From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6CF4FC4167B for ; Fri, 1 Dec 2023 09:27:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378021AbjLAJ1E (ORCPT ); Fri, 1 Dec 2023 04:27:04 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38742 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229455AbjLAJ1B (ORCPT ); Fri, 1 Dec 2023 04:27:01 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 75009194 for ; Fri, 1 Dec 2023 01:27:08 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422826; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Q6FUfFnmqt4IfzZcGlQkVi9fkygYWanokVt8epCh18g=; b=lgvXqUjFJoLwU9+ZZLvtquxTwT6ofi+2y79zdhzkCm+arupJRiVKmMIVcB3lduxwWCFofb MFOL7JDx6+6MFnMmEPZRzTDdRIidDu055pueLPcpiGoOrPv1g40SAikE1AQ96Zg1aCUWsu /RfyywAtAOETUaaOeWDUdTjDg1K5i8v5TCoy1b8UAilHhdNHc0/3AnPNkftGpd67MIalU9 PXMyPG5DMKfCOgRGIYO2Vtiq31A/P7fOfozAca61lrAgMbutkFYtbzGQ38QYnXCUZcDprj jhoN1vY2o7ZgxvN6IUOgYw/d4bOtBFlACxjARMnb88bChF6B1h2PGlbSvNVcnQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422826; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Q6FUfFnmqt4IfzZcGlQkVi9fkygYWanokVt8epCh18g=; b=swIBVCbe9PNsC1cAlRdY84Lq5DKzwDPoPs3oPMIaRGhQn1B3L/aGAyxpp9foQnhZvbP1Cq ixM6qqPcxQvkLZBg== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen Subject: [PATCH v9 01/32] tick-sched: Fix function names in comments Date: Fri, 1 Dec 2023 10:26:23 +0100 Message-Id: <20231201092654.34614-2-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" When referencing functions in comments, it might be helpful to use full function names (including the prefix) to be able to find it when grepping. Signed-off-by: Anna-Maria Behnsen Reviewed-by: Frederic Weisbecker --- v9: New cleanup patch --- kernel/time/tick-sched.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index be77b021e5d6..5c28cc80fd25 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -920,11 +920,11 @@ static void tick_nohz_stop_tick(struct tick_sched *ts= , int cpu) } =20 /* - * nohz_stop_sched_tick() can be called several times before - * nohz_restart_sched_tick() is called. This happens when - * interrupts arrive which do not cause a reschedule. In the - * first call we save the current tick time, so we can restart - * the scheduler tick in nohz_restart_sched_tick(). + * tick_nohz_stop_sched_tick() can be called several times before + * tick_nohz_restart_sched_tick() is called. This happens when + * interrupts arrive which do not cause a reschedule. In the first call + * we save the current tick time, so we can restart the scheduler tick + * in tick_nohz_restart_sched_tick(). */ if (!ts->tick_stopped) { calc_load_nohz_start(); --=20 2.39.2 From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 24994C4167B for ; Fri, 1 Dec 2023 09:27:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378031AbjLAJ1G (ORCPT ); Fri, 1 Dec 2023 04:27:06 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49024 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378004AbjLAJ1C (ORCPT ); Fri, 1 Dec 2023 04:27:02 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E703D10F3 for ; Fri, 1 Dec 2023 01:27:08 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422827; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=jl8/xzU+GiuSpXdMfzNJncPixT2cuPm0ChHCjye17qI=; b=PRcshUeiqQBP6Ypl/4igU9gnAZax/WZ9o6XJmRkijSQlV8N4QjPU98SYISHBREqA75uWZe aXLpTqOnLIMMSJtBYXQmc9vf6PUTFIdnVOz1ssiOQTEDoFR/CgOrgEXe6urDrJO3mAyMOZ CnXf0fRTJBCt/jCRZ09/255zi7frJtW4JTzBXU4m3SuzthrUHV2wDxvgqhxrl/ebelKOPs 8+OOkyFutkDdkDCpN3W0Cap8wApvWQSwQCdI0nIAKfgUSjYLhsPGYaaWgOTaY6tPN0rP28 fpvOInjCw9cXNbhxFLhb7yxte3vgMP/miUKuEACWllOZLXZawL5HAxaL+esNsA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422827; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=jl8/xzU+GiuSpXdMfzNJncPixT2cuPm0ChHCjye17qI=; b=Sb+rjhnebJJIO1g9BgSS4qyOLxH+tt5Barqeak47ZCMSmExPUqtDHBEroBlyuhU1DJydwt x7ySNlMzzhm9QdCg== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen Subject: [PATCH v9 02/32] tick/sched: Cleanup confusing variables Date: Fri, 1 Dec 2023 10:26:24 +0100 Message-Id: <20231201092654.34614-3-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" tick_nohz_stop_tick() contains the expires (u64 variable) and tick (ktime_t) variable. In the beginning the value of expires is written to tick. Afterwards none of the variables is changed. They are only used for checks. Drop the not required variable tick and use always expires instead. Signed-off-by: Anna-Maria Behnsen Reviewed-by: Frederic Weisbecker --- v9: Fix typo in commit message --- kernel/time/tick-sched.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 5c28cc80fd25..89517cfb6510 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -887,7 +887,6 @@ static void tick_nohz_stop_tick(struct tick_sched *ts, = int cpu) struct clock_event_device *dev =3D __this_cpu_read(tick_cpu_device.evtdev= ); u64 basemono =3D ts->timer_expires_base; u64 expires =3D ts->timer_expires; - ktime_t tick =3D expires; =20 /* Make sure we won't be trying to stop it twice in a row. */ ts->timer_expires_base =3D 0; @@ -910,7 +909,7 @@ static void tick_nohz_stop_tick(struct tick_sched *ts, = int cpu) /* Skip reprogram of event if it's not changed */ if (ts->tick_stopped && (expires =3D=3D ts->next_tick)) { /* Sanity check: make sure clockevent is actually programmed */ - if (tick =3D=3D KTIME_MAX || ts->next_tick =3D=3D hrtimer_get_expires(&t= s->sched_timer)) + if (expires =3D=3D KTIME_MAX || ts->next_tick =3D=3D hrtimer_get_expires= (&ts->sched_timer)) return; =20 WARN_ON_ONCE(1); @@ -935,7 +934,7 @@ static void tick_nohz_stop_tick(struct tick_sched *ts, = int cpu) trace_tick_stop(1, TICK_DEP_MASK_NONE); } =20 - ts->next_tick =3D tick; + ts->next_tick =3D expires; =20 /* * If the expiration time =3D=3D KTIME_MAX, then we simply stop @@ -950,11 +949,11 @@ static void tick_nohz_stop_tick(struct tick_sched *ts= , int cpu) } =20 if (ts->nohz_mode =3D=3D NOHZ_MODE_HIGHRES) { - hrtimer_start(&ts->sched_timer, tick, + hrtimer_start(&ts->sched_timer, expires, HRTIMER_MODE_ABS_PINNED_HARD); } else { - hrtimer_set_expires(&ts->sched_timer, tick); - tick_program_event(tick, 1); + hrtimer_set_expires(&ts->sched_timer, expires); + tick_program_event(expires, 1); } } =20 --=20 2.39.2 From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4E9EFC4167B for ; Fri, 1 Dec 2023 09:27:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378041AbjLAJ1J (ORCPT ); Fri, 1 Dec 2023 04:27:09 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49040 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378020AbjLAJ1D (ORCPT ); Fri, 1 Dec 2023 04:27:03 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A980E194 for ; Fri, 1 Dec 2023 01:27:09 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422828; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=TpL4QHNJmRbyjNaiO3+z9ClPjQHijZRgI0ccvQpegrw=; b=UJJq6nocAW/HiAnWK8GyTPEfN1oOPO+9lXJFr9C7HGZTAE0APcdz0FcSis+Nc63mNgmw7f DQPc5vLiU1FzKvIj7a/2povI1jdnoqtwEcyQ4eoRRnp+/slR/Hg9n99bO/DdzE97DLkd42 hzRcSz+mTyBFBysF7BFmGGc2ExkPoKocraYbLNw8ngI0NZCg+akvnglvPjX9CmYUNTqa0i Z+SVu3HynyVTQZWf/Bm6/K2wD5JvHi04S7bTy8ANUEXKTMjAfXPp71O+NVOGHyTBwtWZ62 Jt2ZkJr4otEraNlGF8lGS4zufaLNY/yoA57SyGoui/zyn0ZZgM4oNgQ8y6fvlQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422828; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=TpL4QHNJmRbyjNaiO3+z9ClPjQHijZRgI0ccvQpegrw=; b=iUF3pD/b/ZHxN9ryp4qCxj+pHqQ1FCpLeP6M2yWc0rOxGEeo31fEwzQLExz/7zDZSZEI2g JFxHUEpcXyBZvzCA== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen Subject: [PATCH v9 03/32] tick-sched: Warn when next tick seems to be in the past Date: Fri, 1 Dec 2023 10:26:25 +0100 Message-Id: <20231201092654.34614-4-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" When the next tick is in the past, the delta between basemono and the next tick gets negativ. But the next tick should never be in the past. The negative effect of a wrong next tick might be a stop of the tick and timers might expire late. To prevent expensive debugging when changing underlying code, add a WARN_ON_ONCE into this code path. To prevent complete misbehaviour, also reset next_tick to basemono in this case. Signed-off-by: Anna-Maria Behnsen Reviewed-by: Frederic Weisbecker --- v9: Add reset of next_tick to basemono --- kernel/time/tick-sched.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 89517cfb6510..b1b591de781e 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -839,6 +839,10 @@ static ktime_t tick_nohz_next_event(struct tick_sched = *ts, int cpu) ts->next_timer =3D next_tick; } =20 + /* Make sure next_tick is never before basemono! */ + if (WARN_ON_ONCE(basemono > next_tick)) + next_tick =3D basemono; + /* * If the tick is due in the next period, keep it ticking or * force prod the timer. --=20 2.39.2 From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 298D9C4167B for ; Fri, 1 Dec 2023 09:27:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378054AbjLAJ1P (ORCPT ); Fri, 1 Dec 2023 04:27:15 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49050 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378022AbjLAJ1E (ORCPT ); Fri, 1 Dec 2023 04:27:04 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4E61A10F9 for ; Fri, 1 Dec 2023 01:27:10 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422828; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=EuZUVPY6DwMtX6TE4Diotf1s/Z9ALR3JOBYxJlQlrWo=; b=OrC8zJ88T958APlVyh4kv8Y7X5oRZogAMT9iZFq2jQjoc72FPD8+2eqTlL+ycyJp5uoy5l 3odpYGSoVRz5gOZc3hXdLsfql3bkwEFa/2zEDSpsyfIFvvvxxqEZFmjBeWF+Jr7L72PLnS FvVXfQ26Gi46CvgV/kOtMvpQR57EHIzfxazh71tMy3Bg5YX38DelZ+j5ORZOvg8PbycxVF j3dWdVvRgCkkDrhD/IRT959lpQGbfkPIeSZo9bczNh3QxvTdSAHLnyYPrVF/8GO85T6psE On2U2rnGHPTRScX51/upA2x9kRrpgW2hF4aN7+VFa3SOfqaRuuYbztZrmfHTlA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422828; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=EuZUVPY6DwMtX6TE4Diotf1s/Z9ALR3JOBYxJlQlrWo=; b=iu2NM4FKvnMPiISGNsxUiZzqNgZKsu9vKdvxqy/lJSsO8i3PpLvuA/jj5DgC+UXyMKkZjP y9PPX1zlI6jeCzDQ== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen Subject: [PATCH v9 04/32] tracing/timers: Enhance timer_start tracepoint Date: Fri, 1 Dec 2023 10:26:26 +0100 Message-Id: <20231201092654.34614-5-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" For starting a timer, the timer is enqueued into a bucket of the timer wheel. The bucket expiry is the defacto expiry of the timer but it is not equal the timer expiry because of increasing granularity when bucket is in a higher level of the wheel. To be able to figure out in a trace whether a timer expired in time or not, the bucket expiry time is required as well. Add bucket expiry time to the timer_start tracepoint and thereby simplify the arguments. Signed-off-by: Anna-Maria Behnsen Reviewed-by: Frederic Weisbecker --- v9: New in v9 --- include/trace/events/timer.h | 20 ++++++++++---------- kernel/time/timer.c | 2 +- 2 files changed, 11 insertions(+), 11 deletions(-) diff --git a/include/trace/events/timer.h b/include/trace/events/timer.h index b4bc2828fa09..99ada928d445 100644 --- a/include/trace/events/timer.h +++ b/include/trace/events/timer.h @@ -46,22 +46,21 @@ DEFINE_EVENT(timer_class, timer_init, =20 /** * timer_start - called when the timer is started - * @timer: pointer to struct timer_list - * @expires: the timers expiry time - * @flags: the timers flags + * @timer: pointer to struct timer_list + * @bucket_expiry: the bucket expiry time */ TRACE_EVENT(timer_start, =20 TP_PROTO(struct timer_list *timer, - unsigned long expires, - unsigned int flags), + unsigned long bucket_expiry), =20 - TP_ARGS(timer, expires, flags), + TP_ARGS(timer, bucket_expiry), =20 TP_STRUCT__entry( __field( void *, timer ) __field( void *, function ) __field( unsigned long, expires ) + __field( unsigned long, bucket_expiry ) __field( unsigned long, now ) __field( unsigned int, flags ) ), @@ -69,15 +68,16 @@ TRACE_EVENT(timer_start, TP_fast_assign( __entry->timer =3D timer; __entry->function =3D timer->function; - __entry->expires =3D expires; + __entry->expires =3D timer->expires; + __entry->bucket_expiry =3D bucket_expiry; __entry->now =3D jiffies; - __entry->flags =3D flags; + __entry->flags =3D timer->flags; ), =20 - TP_printk("timer=3D%p function=3D%ps expires=3D%lu [timeout=3D%ld] cpu=3D= %u idx=3D%u flags=3D%s", + TP_printk("timer=3D%p function=3D%ps expires=3D%lu [timeout=3D%ld] bucket= _expiry=3D%lu cpu=3D%u idx=3D%u flags=3D%s", __entry->timer, __entry->function, __entry->expires, (long)__entry->expires - __entry->now, - __entry->flags & TIMER_CPUMASK, + __entry->bucket_expiry, __entry->flags & TIMER_CPUMASK, __entry->flags >> TIMER_ARRAYSHIFT, decode_timer_flags(__entry->flags & TIMER_TRACE_FLAGMASK)) ); diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 63a8ce7177dd..a81d793a43d0 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -606,7 +606,7 @@ static void enqueue_timer(struct timer_base *base, stru= ct timer_list *timer, __set_bit(idx, base->pending_map); timer_set_idx(timer, idx); =20 - trace_timer_start(timer, timer->expires, timer->flags); + trace_timer_start(timer, bucket_expiry); =20 /* * Check whether this is the new first expiring timer. The --=20 2.39.2 From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 98896C4167B for ; Fri, 1 Dec 2023 09:27:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378060AbjLAJ1U (ORCPT ); Fri, 1 Dec 2023 04:27:20 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49056 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378024AbjLAJ1E (ORCPT ); Fri, 1 Dec 2023 04:27:04 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E533510F3 for ; Fri, 1 Dec 2023 01:27:10 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422829; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=x5NV8oLmppm4cChtNeoTUNwitHPz66rl4TtkJG1MsVE=; b=ACJG9BLnPweNxaHJJ9w1pbi+SRth6MXk+ue7mImxGjl0rf06m9//BXNESvnefcAi865eVp HYPHH88orIdDbxTxm6maC9Z7zjntcMuoGw+mucvviLDTWAizOZTFZb3cR0lB9l9VR/YNZ2 XThDs7w8kH85z4y9wuHUBDLuV04+NHpj5jZFQwuLoD1AFW0uGzvPXdi0y5cYapX6LTZk+6 sRTA+PR1Tq1vVNVKY5wlJ92DCMEjLBV6bANERRrmFxSDeOraYXvp1AI2n+5WJao2xPnuyI wNBYPxJiugPji/XfpCYlL5YpmVuIMRE2jvgKEs6sgx+JgsjcFf/iMB+WUJNczg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422829; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=x5NV8oLmppm4cChtNeoTUNwitHPz66rl4TtkJG1MsVE=; b=lV7jqkG/73jefeFGIVa0cvbImUlcDQjpHBuRgRZzzHojWnwJUlYoDZ+Hr85NjGiyrNZEyE 1qQTNsPXqXlEXZCQ== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen Subject: [PATCH v9 05/32] tracing/timers: Add tracepoint for tracking timer base is_idle flag Date: Fri, 1 Dec 2023 10:26:27 +0100 Message-Id: <20231201092654.34614-6-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" When debugging timer code the timer tracepoints are very important. There is no tracepoint when the is_idle flag of the timer base changes. Instead of always adding manually trace_printk(), add tracepoints which can be easily enabled whenever required. Signed-off-by: Anna-Maria Behnsen Reviewed-by: Frederic Weisbecker --- v9: New in v9 --- include/trace/events/timer.h | 20 ++++++++++++++++++++ kernel/time/timer.c | 2 ++ 2 files changed, 22 insertions(+) diff --git a/include/trace/events/timer.h b/include/trace/events/timer.h index 99ada928d445..1ef58a04fc57 100644 --- a/include/trace/events/timer.h +++ b/include/trace/events/timer.h @@ -142,6 +142,26 @@ DEFINE_EVENT(timer_class, timer_cancel, TP_ARGS(timer) ); =20 +TRACE_EVENT(timer_base_idle, + + TP_PROTO(bool is_idle, unsigned int cpu), + + TP_ARGS(is_idle, cpu), + + TP_STRUCT__entry( + __field( bool, is_idle ) + __field( unsigned int, cpu ) + ), + + TP_fast_assign( + __entry->is_idle =3D is_idle; + __entry->cpu =3D cpu; + ), + + TP_printk("is_idle=3D%d cpu=3D%d", + __entry->is_idle, __entry->cpu) +); + #define decode_clockid(type) \ __print_symbolic(type, \ { CLOCK_REALTIME, "CLOCK_REALTIME" }, \ diff --git a/kernel/time/timer.c b/kernel/time/timer.c index a81d793a43d0..46a9b96a3976 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -1964,6 +1964,7 @@ u64 get_next_timer_interrupt(unsigned long basej, u64= basem) if ((expires - basem) > TICK_NSEC) base->is_idle =3D true; } + trace_timer_base_idle(base->is_idle, base->cpu); raw_spin_unlock(&base->lock); =20 return cmp_next_hrtimer_event(basem, expires); @@ -1985,6 +1986,7 @@ void timer_clear_idle(void) * the lock in the exit from idle path. */ base->is_idle =3D false; + trace_timer_base_idle(0, smp_processor_id()); } #endif =20 --=20 2.39.2 From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 83DBDC4167B for ; Fri, 1 Dec 2023 09:27:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378063AbjLAJ1Y (ORCPT ); Fri, 1 Dec 2023 04:27:24 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49060 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378026AbjLAJ1F (ORCPT ); Fri, 1 Dec 2023 04:27:05 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 96970A0 for ; Fri, 1 Dec 2023 01:27:11 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422830; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=l1TO/DAtk+CCicSFDRPTxsBfrzcdsd2AUHicFvATynM=; b=lum7zhufPRoUPgr02L0+nr6ewMLlA4ZRnPpDBOK7AYfwxMTiURnHboUx9eXPXfeoKFWlWj 6K+fqA2/enXeTY+rxTb1bTvUDQYkIxGrDrSeYCwkD//wVE4rieb8koOh1FJ9VKWKxJwN8c q5GIv3tz1v6iJiiz2G8tevShutyRoQfx3C46SmF+O6uXo3GD6xEn8IhesLlwiSlwRNdOqM FawdCuytlVmtP3sAwki1uQ19SKXShRHkMkfB05uFcoe2elWHOYpMt7SLi2qpM36+ZHZwOy k7zjR6RvzhBQMC/lMuSWkxYfSLELuEZ774PPMwGX9rXn+QzoqxVdTm8Aw805Kw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422830; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=l1TO/DAtk+CCicSFDRPTxsBfrzcdsd2AUHicFvATynM=; b=H7J7pHY41+OQTTMvDQDwvpdtt26MF/g+9en13VW2NJaVstqWvRjxzwwVa7UwAS0FehJC09 PPxAiRB4LLN99jBQ== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen Subject: [PATCH v9 06/32] timers: Do not IPI for deferrable timers Date: Fri, 1 Dec 2023 10:26:28 +0100 Message-Id: <20231201092654.34614-7-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Deferrable timers do not prevent CPU from going idle and are not taken into account on idle path. Sending an IPI to a remote CPU when a new first deferrable timer was enqueued will wake up the remote CPU but nothing will be done regarding the deferrable timers. Drop IPI completely when a new first deferrable timer was enqueued. Signed-off-by: Anna-Maria Behnsen Reviewed-by: Frederic Weisbecker --- v9: Only a typo fix v8: Update comment v6: new patch --- kernel/time/timer.c | 15 ++++++--------- 1 file changed, 6 insertions(+), 9 deletions(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 46a9b96a3976..a6e31b09637c 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -571,18 +571,15 @@ static int calc_wheel_index(unsigned long expires, un= signed long clk, static void trigger_dyntick_cpu(struct timer_base *base, struct timer_list *timer) { - if (!is_timers_nohz_active()) - return; - /* - * TODO: This wants some optimizing similar to the code below, but we - * will do that when we switch from push to pull for deferrable timers. + * Deferrable timers do not prevent the CPU from entering dynticks and + * are not taken into account on the idle/nohz_full path. An IPI when a + * new deferrable timer is enqueued will wake up the remote CPU but + * nothing will be done with the deferrable timer base. Therefore skip + * the remote IPI for deferrable timers completely. */ - if (timer->flags & TIMER_DEFERRABLE) { - if (tick_nohz_full_cpu(base->cpu)) - wake_up_nohz_cpu(base->cpu); + if (!is_timers_nohz_active() || timer->flags & TIMER_DEFERRABLE) return; - } =20 /* * We might have to IPI the remote CPU if the base is idle and the --=20 2.39.2 From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D0E0CC4167B for ; Fri, 1 Dec 2023 09:27:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378095AbjLAJ1c (ORCPT ); Fri, 1 Dec 2023 04:27:32 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49066 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378033AbjLAJ1G (ORCPT ); Fri, 1 Dec 2023 04:27:06 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 582C510F3 for ; Fri, 1 Dec 2023 01:27:12 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422830; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=abaveLygv3WKLQ70azOX5Nhmi35F03D2H7Exz6wvRjs=; b=a1nd9r7lEBC9ci6wUVUgi1hN4JCBZlGitekHspDsibrFdu+pl6/3sTyy+324ahw5Rz8T2d uZTYVbFq3MMn/Aork8Mx5jwoQm179AXqZBvu+n7AGwyQykOZik6lmJ1xXTsu7yTmC/HkdF 52j3JYYAPDW4Jg3KME89B0f6l7d6zprctDbQgkcff1pjV5mC/jwRLOLQoZ3LolluWMH1mH YXyx1z+xAybkeuZWQL3+Nc/UPifl2f29OmDqW1J2HjXXELtCOe0OrwmJDsD96TOeH86fTW Sx8OSCuD5mmbxt7QitqcraPf+7fQ+bdykkWeOR1RtVUiv6anLw2D4wUnaXBKgw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422830; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=abaveLygv3WKLQ70azOX5Nhmi35F03D2H7Exz6wvRjs=; b=e0qcp8TwrijRK7VdVHlEYhM6yUkMF56vK2jMfSzEgzTaI8OYcOICJciV0hJSwlLduf3n9/ MRWLn7kdMu364XBA== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen Subject: [PATCH v9 07/32] timers: Move store of next event into __next_timer_interrupt() Date: Fri, 1 Dec 2023 10:26:29 +0100 Message-Id: <20231201092654.34614-8-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Both call sites of __next_timer_interrupt() store the return value directly in base->next_expiry. Move the store into __next_timer_interrupt() and to make its purpose more clear, rename the function to next_expiry_recalc(). No functional change. Signed-off-by: Anna-Maria Behnsen Reviewed-by: Thomas Gleixner Reviewed-by: Frederic Weisbecker --- v9: Typo fix only v6: Fix typos in commit message and drop not required return as suggested by Peter Zijlstra v4: rename function as suggested by Frederic Weisbecker --- kernel/time/timer.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index a6e31b09637c..3ca706db1d20 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -1800,8 +1800,10 @@ static int next_pending_bucket(struct timer_base *ba= se, unsigned offset, /* * Search the first expiring timer in the various clock levels. Caller must * hold base->lock. + * + * Store next expiry time in base->next_expiry. */ -static unsigned long __next_timer_interrupt(struct timer_base *base) +static void next_expiry_recalc(struct timer_base *base) { unsigned long clk, next, adj; unsigned lvl, offset =3D 0; @@ -1867,10 +1869,9 @@ static unsigned long __next_timer_interrupt(struct t= imer_base *base) clk +=3D adj; } =20 + base->next_expiry =3D next; base->next_expiry_recalc =3D false; base->timers_pending =3D !(next =3D=3D base->clk + NEXT_TIMER_MAX_DELTA); - - return next; } =20 #ifdef CONFIG_NO_HZ_COMMON @@ -1930,7 +1931,7 @@ u64 get_next_timer_interrupt(unsigned long basej, u64= basem) =20 raw_spin_lock(&base->lock); if (base->next_expiry_recalc) - base->next_expiry =3D __next_timer_interrupt(base); + next_expiry_recalc(base); nextevt =3D base->next_expiry; =20 /* @@ -2015,7 +2016,7 @@ static inline void __run_timers(struct timer_base *ba= se) WARN_ON_ONCE(!levels && !base->next_expiry_recalc && base->timers_pending); base->clk++; - base->next_expiry =3D __next_timer_interrupt(base); + next_expiry_recalc(base); =20 while (levels--) expire_timers(base, heads + levels); --=20 2.39.2 From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1B23DC4167B for ; Fri, 1 Dec 2023 09:27:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378082AbjLAJ12 (ORCPT ); Fri, 1 Dec 2023 04:27:28 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49080 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378034AbjLAJ1G (ORCPT ); Fri, 1 Dec 2023 04:27:06 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 092D610F9 for ; Fri, 1 Dec 2023 01:27:13 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422831; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=gO/udsWQ+bQJ+e/QIsLEl2DMKpANRb9evAUW1EC/BoI=; b=eIQqB/WQldigQLY0Gair11m9tMLsVtE1Ib3/oPytcBEd0/qDyfDCkRvTegLi/ZOrzT7FAp m6oEWHBnwrgAMkh9+bzPfsxav1MuLLAhzI9oyKAjTVdcqH2yPJXlWIy6lJF+SCwvcwKr1X 7Pp+MFb8jhvlCfqGjEwPSRKuAt9kEkCnabNBehpLjPbkXIZ8K5IoNUljS6/u50/eSfQgUf VSThVmxWrJu8mpM5Qi5/FgIUXg+bYlY8yit7NI2v3s5jB8u5yF0EAH4bk1q8dEM325dil4 5dNv4T2hfHZdbg62aF0lh9ESjOV1r6Dbv991Z5BpJBgmgLhuWM8DC8/sKkvU4g== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422831; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=gO/udsWQ+bQJ+e/QIsLEl2DMKpANRb9evAUW1EC/BoI=; b=DLkvoQ1hQ176JTziAZ/kfHhh7nRRJW7GCXqvS2BDCpVLtS0WNM3KRr3h6ZYLXNylsajT5P e48W33DVK1JYzuDw== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen Subject: [PATCH v9 08/32] timers: Clarify check in forward_timer_base() Date: Fri, 1 Dec 2023 10:26:30 +0100 Message-Id: <20231201092654.34614-9-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" The current check whether a forward of the timer base is required can be simplified by using an already existing comparison function which is easier to read. The related comment is outdated and was not updated when the check changed in commit 36cd28a4cdd0 ("timers: Lower base clock forwarding threshold"). Use time_before_eq() for the check and replace the comment by copying the comment from the same check inside get_next_timer_interrupt(). Move the precious information of the outdated comment to the proper place in __run_timers(). No functional change. Signed-off-by: Anna-Maria Behnsen Reviewed-by: Frederic Weisbecker --- v9: Move precious information of outdated comment to proper place (as suggested by Frederic) --- kernel/time/timer.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 3ca706db1d20..66bac56909ba 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -944,11 +944,10 @@ static inline void forward_timer_base(struct timer_ba= se *base) unsigned long jnow =3D READ_ONCE(jiffies); =20 /* - * No need to forward if we are close enough below jiffies. - * Also while executing timers, base->clk is 1 offset ahead - * of jiffies to avoid endless requeuing to current jiffies. + * Check whether we can forward the base. We can only do that when + * @basej is past base->clk otherwise we might rewind base->clk. */ - if ((long)(jnow - base->clk) < 1) + if (time_before_eq(jnow, base->clk)) return; =20 /* @@ -2015,6 +2014,10 @@ static inline void __run_timers(struct timer_base *b= ase) */ WARN_ON_ONCE(!levels && !base->next_expiry_recalc && base->timers_pending); + /* + * While executing timers, base->clk is set 1 offset ahead of + * jiffies to avoid endless requeuing to current jiffies. + */ base->clk++; next_expiry_recalc(base); =20 --=20 2.39.2 From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C7309C10F04 for ; Fri, 1 Dec 2023 09:27:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378101AbjLAJ1e (ORCPT ); Fri, 1 Dec 2023 04:27:34 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49106 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378035AbjLAJ1H (ORCPT ); Fri, 1 Dec 2023 04:27:07 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AB89710FC for ; Fri, 1 Dec 2023 01:27:13 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422832; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=NX2OtYZi8wYLdH4/EBEFqndbEahIgfLRJkHvTArpnf8=; b=1ggAH7wj+axl9TgEGJFZ0/uAb3cs+EW+X/QNAiGkGxhubO1WQ+ye67f57geO0uUgLmkZkL HvIPqcMu+1kgF6qnb72qlUj9+XGiJQS0qO4JNx9UYCX5iEGrK9FyAavNTYTSNwNpE9ghjY AfDEUuun8UgRzUrq7qEydbw/pXjJWUdOCUkmVDsiEWDsuPTYlj3u1B6Lr6HDIQzL2LG76+ kQcf4y/R6aiDYIlAQdaPPdghBaLiASdU2NCpEJEfA9zsdj9Hf9ZpuCbdej0w3aUOfxFDWQ ZNCAwSvoyAy9aMCi13puWX28GeFSL9rfPfL9btfjxsrP8FzpUmD8JWwSRMXaOQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422832; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=NX2OtYZi8wYLdH4/EBEFqndbEahIgfLRJkHvTArpnf8=; b=FWFW6/pnQLncFa4pPnDKR90jyaAVnwrvB+ARbjuC6CzkQWAsi8kK9Gc2XmjQxcA0arZv6p oCcqOjNaJyyrPcDg== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen Subject: [PATCH v9 09/32] timers: Split out forward timer base functionality Date: Fri, 1 Dec 2023 10:26:31 +0100 Message-Id: <20231201092654.34614-10-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Forwarding timer base is done when the next expiry value is calculated and when a new timer is enqueued. When the next expiry value is calculated the jiffies value is already available and does not need to be reread a second time. Splitting out the forward timer base functionality to make it executable via both contextes - those where jiffies are already known and those, where jiffies need to be read. No functional change. Signed-off-by: Anna-Maria Behnsen Reviewed-by: Frederic Weisbecker --- kernel/time/timer.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 66bac56909ba..e289cbd84e8c 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -939,30 +939,34 @@ get_target_base(struct timer_base *base, unsigned tfl= ags) return get_timer_this_cpu_base(tflags); } =20 -static inline void forward_timer_base(struct timer_base *base) +static inline void __forward_timer_base(struct timer_base *base, + unsigned long basej) { - unsigned long jnow =3D READ_ONCE(jiffies); - /* * Check whether we can forward the base. We can only do that when * @basej is past base->clk otherwise we might rewind base->clk. */ - if (time_before_eq(jnow, base->clk)) + if (time_before_eq(basej, base->clk)) return; =20 /* * If the next expiry value is > jiffies, then we fast forward to * jiffies otherwise we forward to the next expiry value. */ - if (time_after(base->next_expiry, jnow)) { - base->clk =3D jnow; + if (time_after(base->next_expiry, basej)) { + base->clk =3D basej; } else { if (WARN_ON_ONCE(time_before(base->next_expiry, base->clk))) return; base->clk =3D base->next_expiry; } + } =20 +static inline void forward_timer_base(struct timer_base *base) +{ + __forward_timer_base(base, READ_ONCE(jiffies)); +} =20 /* * We are using hashed locking: Holding per_cpu(timer_bases[x]).lock means --=20 2.39.2 From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 10BB9C4167B for ; Fri, 1 Dec 2023 09:27:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378027AbjLAJ1h (ORCPT ); Fri, 1 Dec 2023 04:27:37 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41208 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378065AbjLAJ1U (ORCPT ); Fri, 1 Dec 2023 04:27:20 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 44A8B171A for ; Fri, 1 Dec 2023 01:27:14 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422833; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=+S43URzdkm4GE5deeh35HedlVNn9pKmfGb0vCPSVNJU=; b=el5AdGLCIQZcbBus9nb/xgs+vY+Tv76/155OcrpNkNOjUWHu2Iay04ijEup/CZKYAfF+qh sLqmjFN9GHKVRUzf9cRZklprE52pJ9L8kUfKjnGdDNVQK2XqUFEQ+6+hzipfaedbaRthZm 6Kl2Obge+HPzfqeWxSHmaScooCQbrXk8SOQ3Ik/mN0vTv4iSaOEZbdKEONwbdxIV5BJU/E WNrcDanyKol7UClRMoZbNgCpdqMNa08bdC3xYLNna5+c2HQf/8kKGMT+GtVdqx2WIXo3RJ RgKdDCKh3NQUBx0fiAdJKLos3M2mXq790/QjjGt3MOHAEXZREpaJo/p+qtLbPw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422833; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=+S43URzdkm4GE5deeh35HedlVNn9pKmfGb0vCPSVNJU=; b=HxtFSzHBtGc0DacUydRzFJpAQaTMJ4mc5tul79/rcY9HP9L9pECbfeBHsmnvjQJFudbZJQ DO5tluaLRIL1/YCA== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen Subject: [PATCH v9 10/32] timers: Use already existing function for forwarding timer base Date: Fri, 1 Dec 2023 10:26:32 +0100 Message-Id: <20231201092654.34614-11-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" There is an already existing function for forwarding the timer base. Forwarding the timer base is implemented directly in get_next_timer_interrupt() as well. Remove the code duplication and invoke __forward_timer_base() instead. Signed-off-by: Anna-Maria Behnsen Reviewed-by: Frederic Weisbecker --- kernel/time/timer.c | 10 ++-------- 1 file changed, 2 insertions(+), 8 deletions(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index e289cbd84e8c..fee42dda8237 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -1939,15 +1939,9 @@ u64 get_next_timer_interrupt(unsigned long basej, u6= 4 basem) =20 /* * We have a fresh next event. Check whether we can forward the - * base. We can only do that when @basej is past base->clk - * otherwise we might rewind base->clk. + * base. */ - if (time_after(basej, base->clk)) { - if (time_after(nextevt, basej)) - base->clk =3D basej; - else if (time_after(nextevt, base->clk)) - base->clk =3D nextevt; - } + __forward_timer_base(base, basej); =20 if (time_before_eq(nextevt, basej)) { expires =3D basem; --=20 2.39.2 From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D46B6C4167B for ; Fri, 1 Dec 2023 09:27:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378125AbjLAJ1r (ORCPT ); Fri, 1 Dec 2023 04:27:47 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54352 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378050AbjLAJ1W (ORCPT ); Fri, 1 Dec 2023 04:27:22 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 03BF8171C for ; Fri, 1 Dec 2023 01:27:14 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422833; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=OjHpvhdurB+xA/Q5Qjg90zYVhHrCM9ixI3FXScsHyt8=; b=KKGSI58SUmBD5Umq/6Q4hIqdbuQjSnzca6zjvAccM2ulw1J6bMv4sXp813ZrMIM1hVtQVH MspT53qWCRzuqvVxUVkoZ04eH80zx/S7MKiw82z+OJKUhRBCi4XQI0/1WlXc2sqf13LW5W IliQXqnyGckto5IWaqLX7GyU0+RzB8zepKOF/AnVpcJ+6MNpR5HCo26arlDmQf94v6jG3J wUax+CBx48cBjE5Axx9p7sO19r8k8gYwRvLBrc5EXDJDpWBcX66pOL4Ys/OiTDUdjW/xc+ t8UrhivzaOHFUQCi/N8COFa/nSqBBhaGOO7CG3xoQe4tqPVGSUhVWd0rxerE7Q== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422833; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=OjHpvhdurB+xA/Q5Qjg90zYVhHrCM9ixI3FXScsHyt8=; b=Aml3ir39NvV+AcjCiHTJCqqN6AvMpP5DwCTpdnC7/AHu45ZPNUabml56+ThbNpQsMZFpb2 eyfv64zM1EqeFwBg== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen Subject: [PATCH v9 11/32] timers: Rework idle logic Date: Fri, 1 Dec 2023 10:26:33 +0100 Message-Id: <20231201092654.34614-12-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Thomas Gleixner To improve readability of the code, split base->idle calculation and expires calculation into separate parts. While at it, update the comment about timer base idle marking. Thereby the following subtle change happens if the next event is just one jiffy ahead and the tick was already stopped: Originally base->is_idle remains true in this situation. Now base->is_idle turns to false. This may spare an IPI if a timer is enqueued remotely to an idle CPU that is going to tick on the next jiffy. Signed-off-by: Thomas Gleixner Signed-off-by: Anna-Maria Behnsen Reviewed-by: Frederic Weisbecker --- v9: Re-ordering to not hurt the eyes and update comment v4: Change condition to force 0 delta and update commit message (Frederic) --- kernel/time/timer.c | 31 ++++++++++++++++--------------- 1 file changed, 16 insertions(+), 15 deletions(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index fee42dda8237..0826018d9873 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -1943,22 +1943,23 @@ u64 get_next_timer_interrupt(unsigned long basej, u= 64 basem) */ __forward_timer_base(base, basej); =20 - if (time_before_eq(nextevt, basej)) { - expires =3D basem; - base->is_idle =3D false; - } else { - if (base->timers_pending) - expires =3D basem + (u64)(nextevt - basej) * TICK_NSEC; - /* - * If we expect to sleep more than a tick, mark the base idle. - * Also the tick is stopped so any added timer must forward - * the base clk itself to keep granularity small. This idle - * logic is only maintained for the BASE_STD base, deferrable - * timers may still see large granularity skew (by design). - */ - if ((expires - basem) > TICK_NSEC) - base->is_idle =3D true; + if (base->timers_pending) { + /* If we missed a tick already, force 0 delta */ + if (time_before(nextevt, basej)) + nextevt =3D basej; + expires =3D basem + (u64)(nextevt - basej) * TICK_NSEC; } + + /* + * Base is idle if the next event is more than a tick away. + * + * If the base is marked idle then any timer add operation must forward + * the base clk itself to keep granularity small. This idle logic is + * only maintained for the BASE_STD base, deferrable timers may still + * see large granularity skew (by design). + */ + base->is_idle =3D time_after(nextevt, basej + 1); + trace_timer_base_idle(base->is_idle, base->cpu); raw_spin_unlock(&base->lock); =20 --=20 2.39.2 From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 35A38C4167B for ; Fri, 1 Dec 2023 09:27:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378120AbjLAJ1n (ORCPT ); Fri, 1 Dec 2023 04:27:43 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54358 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378055AbjLAJ1W (ORCPT ); Fri, 1 Dec 2023 04:27:22 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A3A521725 for ; Fri, 1 Dec 2023 01:27:15 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422834; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=nZi/SXfoi2GICSzM+IYBAVSlO8Hm1DXEFr76jQHYOZ0=; b=lPUu/u3782O76F4tssDfbbwJSu1UYJWRXA1YF1HFvK1m8kbs0zLQsUh/Qrq0SympHt1Xn4 fWs6pLLsziRXsDGGtVSkmgIluUmEPyOt49N0oJuW1GpqQsDrQiTwLCGHDYPxL2sHNl8pO8 uZrfXgDRa3Soql/IDz++WAZHigpe67VrkWm7MrhlkMdDJb1cuTVJRBpNVrj0k0qs67dVi3 SnfBc962XKiwdxw27XZSz4hJUgXOfPYnpxuSOBDbSvDj36Sfa0N/0H08AMFC8K3OePFC/t LsAllTQBY9b+fu99vTafsfRYXEb2PxTXLZsynXnrqJJ34TflfOYmg29flJ7ItA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422834; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=nZi/SXfoi2GICSzM+IYBAVSlO8Hm1DXEFr76jQHYOZ0=; b=DGxDnst2vjquka22zFxBnL29sukEirkFvC4s2bWFecYQdCP9TQh2tKsQYBTAwCLj3xIhX6 heDteX2CRHR+6lAg== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen Subject: [PATCH v9 12/32] timers: Fix nextevt calculation when no timers are pending Date: Fri, 1 Dec 2023 10:26:34 +0100 Message-Id: <20231201092654.34614-13-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" When no timer is queued into an empty timer base, the next_expiry will not be updated. It was originally calculated as base->clk + NEXT_TIMER_MAX_DELTA When the timer base stays empty long enough (> NEXT_TIMER_MAX_DELTA), the next_expiry value of the empty base suggests that there is a timer pending soon. This might be more a kind of a theoretical problem, but the fix doesn't hurt. Use only base->next_expiry value as nextevt when timers are pending. Otherwise nextevt will be jiffies + NEXT_TIMER_MAX_DELTA. As all information is in place, update base->next_expiry value of the empty timer base as well. Signed-off-by: Anna-Maria Behnsen Reviewed-by: Frederic Weisbecker --- v9: New patch --- kernel/time/timer.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 0826018d9873..4dffe966424c 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -1922,8 +1922,8 @@ static u64 cmp_next_hrtimer_event(u64 basem, u64 expi= res) u64 get_next_timer_interrupt(unsigned long basej, u64 basem) { struct timer_base *base =3D this_cpu_ptr(&timer_bases[BASE_STD]); + unsigned long nextevt =3D basej + NEXT_TIMER_MAX_DELTA; u64 expires =3D KTIME_MAX; - unsigned long nextevt; =20 /* * Pretend that there is no timer pending if the cpu is offline. @@ -1935,7 +1935,6 @@ u64 get_next_timer_interrupt(unsigned long basej, u64= basem) raw_spin_lock(&base->lock); if (base->next_expiry_recalc) next_expiry_recalc(base); - nextevt =3D base->next_expiry; =20 /* * We have a fresh next event. Check whether we can forward the @@ -1944,10 +1943,20 @@ u64 get_next_timer_interrupt(unsigned long basej, u= 64 basem) __forward_timer_base(base, basej); =20 if (base->timers_pending) { + nextevt =3D base->next_expiry; + /* If we missed a tick already, force 0 delta */ if (time_before(nextevt, basej)) nextevt =3D basej; expires =3D basem + (u64)(nextevt - basej) * TICK_NSEC; + } else { + /* + * Move next_expiry for the empty base into the future to + * prevent a unnecessary raise of the timer softirq when the + * next_expiry value will be reached even if there is no timer + * pending. + */ + base->next_expiry =3D nextevt; } =20 /* --=20 2.39.2 From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2E83FC4167B for ; Fri, 1 Dec 2023 09:27:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378075AbjLAJ1k (ORCPT ); Fri, 1 Dec 2023 04:27:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41242 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378047AbjLAJ1W (ORCPT ); Fri, 1 Dec 2023 04:27:22 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7992E172E for ; Fri, 1 Dec 2023 01:27:16 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422835; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=eWAzXEfpMywLlqp587KxIHRrk44Rp7dtxL6JlN1/eF4=; b=nrPDcWG6y+EdgnAwLZJrMGEaTSj4fpLZbHu1F5MYX4pNfm8XwdDmfbaq3+Qfw75U13WXlN Wn/03lvZN5wgl5keYEfUyqe+Ren56ovfCTN73gvsCHyVcgnrOaxR6UU35FeZKoPn9cXLqx HnQJ41b5XrnUqb9KygJlhKObBRbD0CBisK8MgF7pi4EzW1AySz6TKSzWbQeWz/O25sSOGI mUcxSvIcwOCrfPKPMKcjfpRPDQXVMO/6pXJSNwHje+BVCkdOMwdyCG52Y5obMfOKXuqsrz xPK5vVvU53qVkzQ12pNGeND+dF67+YhA8Kfco1uSKz+rFzdJHkWzTHobUjGZJg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422835; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=eWAzXEfpMywLlqp587KxIHRrk44Rp7dtxL6JlN1/eF4=; b=ejl4p2jWf2hUodAxU46BdlFPsS0jUview2NzC2fTxisTms7SzXjFDnFPfiT065gMEKHznq UDzdpbW485YF6UAw== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen Subject: [PATCH v9 13/32] timers: Restructure get_next_timer_interrupt() Date: Fri, 1 Dec 2023 10:26:35 +0100 Message-Id: <20231201092654.34614-14-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" get_next_timer_interrupt() contains two parts for the next timer interrupt calculation. Those two parts are separated by forwarding the base clock. But the second part does not depend on the forwarded base clock. Therefore restructure get_next_timer_interrupt() to keep things together which belong together. No functional change. Signed-off-by: Anna-Maria Behnsen --- v9: New patch to eases patch "timers: Split out get next timer functionalit= y" --- kernel/time/timer.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 4dffe966424c..9d377ebb7395 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -1936,12 +1936,6 @@ u64 get_next_timer_interrupt(unsigned long basej, u6= 4 basem) if (base->next_expiry_recalc) next_expiry_recalc(base); =20 - /* - * We have a fresh next event. Check whether we can forward the - * base. - */ - __forward_timer_base(base, basej); - if (base->timers_pending) { nextevt =3D base->next_expiry; =20 @@ -1959,6 +1953,12 @@ u64 get_next_timer_interrupt(unsigned long basej, u6= 4 basem) base->next_expiry =3D nextevt; } =20 + /* + * We have a fresh next event. Check whether we can forward the + * base. + */ + __forward_timer_base(base, basej); + /* * Base is idle if the next event is more than a tick away. * --=20 2.39.2 From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B7ABAC4167B for ; Fri, 1 Dec 2023 09:28:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378138AbjLAJ1v (ORCPT ); Fri, 1 Dec 2023 04:27:51 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41208 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378030AbjLAJ1W (ORCPT ); Fri, 1 Dec 2023 04:27:22 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 44E0F1731 for ; Fri, 1 Dec 2023 01:27:17 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422835; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=JrX+uOonkdlgOULBTRJ+tPCkJgZ/y8AeNa7bH45nGMA=; b=D5XrFnLBsbY5lkVSgkpnNLWdRfAh8BRN6Ig8U6EK79iQ7Zz6/XWyZ79d2M5HXR5I74m+Pg S2hARumZwAdv8qw3krKtquSgSCKHqHiLz+BWE4T0RiujFRl5MC0AqCSeVPs3cVP7Qy8QTt BhTFkQaRlJPXDnkOTYvZAkLppDQPesiYyCwodQABI0CGKBDr6ryeU3PvmE3eKTtphN6BN5 vZ6ZXUk6bXGQAKaLiOeCpTyaEQEBor8J2m5oteVUECBzkbP15etoSFY8qeoidjKwOILaA6 vmJKuQ90tjl4f8jjJJDBqc7RPGnDbvC09YC3jWkqB+JV1J73vhnXmj6HVmW2MQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422835; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=JrX+uOonkdlgOULBTRJ+tPCkJgZ/y8AeNa7bH45nGMA=; b=Mla+AechBwy5Fc5CLuvFJk+kdfUcABs97vqRw9ixz3j4sPEqx0f9eeiOBVWA3gXcymuY6G 1eT8gT1dpYXIoHCA== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen Subject: [PATCH v9 14/32] timers: Split out get next timer interrupt Date: Fri, 1 Dec 2023 10:26:36 +0100 Message-Id: <20231201092654.34614-15-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Split out get_next_timer_interrupt() to be able to extend it and make it reusable for other call sites. No functional change. Signed-off-by: Anna-Maria Behnsen --- v9: Move whole get_next_timer_interrupt() into a separate function instead of splitting the bits and pieces. --- kernel/time/timer.c | 23 ++++++++++++++--------- 1 file changed, 14 insertions(+), 9 deletions(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 9d377ebb7395..c9f7f86e95fd 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -1911,15 +1911,7 @@ static u64 cmp_next_hrtimer_event(u64 basem, u64 exp= ires) return DIV_ROUND_UP_ULL(nextevt, TICK_NSEC) * TICK_NSEC; } =20 -/** - * get_next_timer_interrupt - return the time (clock mono) of the next tim= er - * @basej: base time jiffies - * @basem: base time clock monotonic - * - * Returns the tick aligned clock monotonic time of the next pending - * timer or KTIME_MAX if no timer is pending. - */ -u64 get_next_timer_interrupt(unsigned long basej, u64 basem) +static inline u64 __get_next_timer_interrupt(unsigned long basej, u64 base= m) { struct timer_base *base =3D this_cpu_ptr(&timer_bases[BASE_STD]); unsigned long nextevt =3D basej + NEXT_TIMER_MAX_DELTA; @@ -1975,6 +1967,19 @@ u64 get_next_timer_interrupt(unsigned long basej, u6= 4 basem) return cmp_next_hrtimer_event(basem, expires); } =20 +/** + * get_next_timer_interrupt() - return the time (clock mono) of the next t= imer + * @basej: base time jiffies + * @basem: base time clock monotonic + * + * Returns the tick aligned clock monotonic time of the next pending + * timer or KTIME_MAX if no timer is pending. + */ +u64 get_next_timer_interrupt(unsigned long basej, u64 basem) +{ + return __get_next_timer_interrupt(basej, basem); +} + /** * timer_clear_idle - Clear the idle state of the timer base * --=20 2.39.2 From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DF905C10F07 for ; Fri, 1 Dec 2023 09:28:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378098AbjLAJ16 (ORCPT ); Fri, 1 Dec 2023 04:27:58 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54420 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378084AbjLAJ12 (ORCPT ); Fri, 1 Dec 2023 04:27:28 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 69138173A for ; Fri, 1 Dec 2023 01:27:18 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422836; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=XDkZ99bgjbwfcazN7cvP/yxsFnqYGi5j6mcGkkMlXpc=; b=i5sS1zVbA72IjyBXtjc3SlWfoRyosMorQZH3qX/weLjOiNry7I/7+4ZgkwI7rmOt1p/UXO 3ww8mo0MOUqO+0Diq1FG02gACn2a5p8pLaKx4fFpd3Yawe9JQAKrWl12KLbQwY1IMXXpAh 5W45BtdaHxyhbNgs8peW4ql2RF8W+ZB6yl2g9nfSMXzk+zG6IaY0ToMyTnMmUuM/iuz3mQ bqLuNhAa5FwwvNfTHeMY4zkeaW0719YMrlCGBsafijBw499DvJ87pFui7vqLqhZttIzHFJ rv22HaG2jZbCCvq2dWwD47XGS1nPvy+Bj4UvuGISVk33iYxk+xxsOgkyHOJrtQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422836; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=XDkZ99bgjbwfcazN7cvP/yxsFnqYGi5j6mcGkkMlXpc=; b=pmacNEm05CQnWjnwz89fRs+iAO6fnmS1N9jqQgq915NFXVkq+NFsHJgid3bh8sVzGv0A5B dpET6y0V972a7nCA== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen Subject: [PATCH v9 15/32] timers: Move marking timer bases idle into tick_nohz_stop_tick() Date: Fri, 1 Dec 2023 10:26:37 +0100 Message-Id: <20231201092654.34614-16-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" The timer base is marked idle when get_next_timer_interrupt() is executed. But the decision whether the tick will be stopped and whether the system is able to go idle is done later. When the timer bases is marked idle and a new first timer is enqueued remote an IPI is raised. Even if it is not required because the tick is not stopped and the timer base is evaluated again at the next tick. To prevent this, the timer base is marked idle in tick_nohz_stop_tick() and get_next_timer_interrupt() is streamlined by only looking for the next timer interrupt. All other work is postponed to timer_base_try_to_set_idle() which is called by tick_nohz_stop_tick(). While at it fix some nearby whitespace damage as well. Signed-off-by: Anna-Maria Behnsen --- v9: - update to the changes of the patch before - Cleanup logic in tick_nohz_stop_tick() after executing timer_base_try= _to_set_idle() --- kernel/time/tick-internal.h | 1 + kernel/time/tick-sched.c | 46 ++++++++++++++++++++++++++--------- kernel/time/timer.c | 48 ++++++++++++++++++++++++++++--------- 3 files changed, 73 insertions(+), 22 deletions(-) diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h index 649f2b48e8f0..dc12a938f00f 100644 --- a/kernel/time/tick-internal.h +++ b/kernel/time/tick-internal.h @@ -164,6 +164,7 @@ static inline void timers_update_nohz(void) { } DECLARE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases); =20 extern u64 get_next_timer_interrupt(unsigned long basej, u64 basem); +u64 timer_base_try_to_set_idle(unsigned long basej, u64 basem, bool *idle); void timer_clear_idle(void); =20 #define CLOCK_SET_WALL \ diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index b1b591de781e..3e1cdb7c6966 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -849,11 +849,6 @@ static ktime_t tick_nohz_next_event(struct tick_sched = *ts, int cpu) */ delta =3D next_tick - basemono; if (delta <=3D (u64)TICK_NSEC) { - /* - * Tell the timer code that the base is not idle, i.e. undo - * the effect of get_next_timer_interrupt(): - */ - timer_clear_idle(); /* * We've not stopped the tick yet, and there's a timer in the * next period, so no point in stopping it either, bail. @@ -889,12 +884,41 @@ static ktime_t tick_nohz_next_event(struct tick_sched= *ts, int cpu) static void tick_nohz_stop_tick(struct tick_sched *ts, int cpu) { struct clock_event_device *dev =3D __this_cpu_read(tick_cpu_device.evtdev= ); + unsigned long basejiff =3D ts->last_jiffies; u64 basemono =3D ts->timer_expires_base; - u64 expires =3D ts->timer_expires; + bool timer_idle; + u64 expires; =20 /* Make sure we won't be trying to stop it twice in a row. */ ts->timer_expires_base =3D 0; =20 + /* + * Now the tick should be stopped definitely - so the timer base needs + * to be marked idle as well to not miss a newly queued timer. + */ + expires =3D timer_base_try_to_set_idle(basejiff, basemono, &timer_idle); + if (!timer_idle) { + /* + * Do not clear tick_stopped here when it was already set - it + * will be retained on the next idle iteration when the tick + * expired earlier than expected. + */ + expires =3D basemono + TICK_NSEC; + } else if (expires > ts->timer_expires) { + /* + * This path could only happen when the first timer was removed + * between calculating the possible sleep length and now (when + * high resolution mode is not active, timer could also be a + * hrtimer). + * + * We have to stick to the original calculated expiry value to + * not stop the tick for too long with a shallow C-state (which + * was programmed by cpuidle because of an early next expiration + * value). + */ + expires =3D ts->timer_expires; + } + /* * If this CPU is the one which updates jiffies, then give up * the assignment and let it be taken by the CPU which runs @@ -930,6 +954,10 @@ static void tick_nohz_stop_tick(struct tick_sched *ts,= int cpu) * in tick_nohz_restart_sched_tick(). */ if (!ts->tick_stopped) { + /* If the timer base is not idle, retain the tick. */ + if (!timer_idle) + return; + calc_load_nohz_start(); quiet_vmstat(); =20 @@ -991,7 +1019,7 @@ static void tick_nohz_restart_sched_tick(struct tick_s= ched *ts, ktime_t now) touch_softlockup_watchdog_sched(); =20 /* Cancel the scheduled timer and restore the tick: */ - ts->tick_stopped =3D 0; + ts->tick_stopped =3D 0; tick_nohz_restart(ts, now); } =20 @@ -1147,10 +1175,6 @@ void tick_nohz_idle_stop_tick(void) void tick_nohz_idle_retain_tick(void) { tick_nohz_retain_tick(this_cpu_ptr(&tick_cpu_sched)); - /* - * Undo the effect of get_next_timer_interrupt() called from - * tick_nohz_next_event(). - */ timer_clear_idle(); } =20 diff --git a/kernel/time/timer.c b/kernel/time/timer.c index c9f7f86e95fd..df6558f62e6f 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -1911,7 +1911,8 @@ static u64 cmp_next_hrtimer_event(u64 basem, u64 expi= res) return DIV_ROUND_UP_ULL(nextevt, TICK_NSEC) * TICK_NSEC; } =20 -static inline u64 __get_next_timer_interrupt(unsigned long basej, u64 base= m) +static inline u64 __get_next_timer_interrupt(unsigned long basej, u64 base= m, + bool *idle) { struct timer_base *base =3D this_cpu_ptr(&timer_bases[BASE_STD]); unsigned long nextevt =3D basej + NEXT_TIMER_MAX_DELTA; @@ -1921,8 +1922,11 @@ static inline u64 __get_next_timer_interrupt(unsigne= d long basej, u64 basem) * Pretend that there is no timer pending if the cpu is offline. * Possible pending timers will be migrated later to an active cpu. */ - if (cpu_is_offline(smp_processor_id())) + if (cpu_is_offline(smp_processor_id())) { + if (idle) + *idle =3D true; return expires; + } =20 raw_spin_lock(&base->lock); if (base->next_expiry_recalc) @@ -1952,16 +1956,24 @@ static inline u64 __get_next_timer_interrupt(unsign= ed long basej, u64 basem) __forward_timer_base(base, basej); =20 /* - * Base is idle if the next event is more than a tick away. - * - * If the base is marked idle then any timer add operation must forward - * the base clk itself to keep granularity small. This idle logic is - * only maintained for the BASE_STD base, deferrable timers may still - * see large granularity skew (by design). + * Set base->is_idle only when caller is timer_base_try_to_set_idle() */ - base->is_idle =3D time_after(nextevt, basej + 1); + if (idle) { + /* + * Base is idle if the next event is more than a tick away. + * + * If the base is marked idle then any timer add operation must + * forward the base clk itself to keep granularity small. This + * idle logic is only maintained for the BASE_STD base, + * deferrable timers may still see large granularity skew (by + * design). + */ + if (!base->is_idle) + base->is_idle =3D time_after(nextevt, basej + 1); + *idle =3D base->is_idle; + trace_timer_base_idle(base->is_idle, base->cpu); + } =20 - trace_timer_base_idle(base->is_idle, base->cpu); raw_spin_unlock(&base->lock); =20 return cmp_next_hrtimer_event(basem, expires); @@ -1977,7 +1989,21 @@ static inline u64 __get_next_timer_interrupt(unsigne= d long basej, u64 basem) */ u64 get_next_timer_interrupt(unsigned long basej, u64 basem) { - return __get_next_timer_interrupt(basej, basem); + return __get_next_timer_interrupt(basej, basem, NULL); +} + +/** + * timer_base_try_to_set_idle() - Try to set the idle state of the timer b= ases + * @basej: base time jiffies + * @basem: base time clock monotonic + * @idle: pointer to store the value of timer_base->is_idle + * + * Returns the tick aligned clock monotonic time of the next pending + * timer or KTIME_MAX if no timer is pending. + */ +u64 timer_base_try_to_set_idle(unsigned long basej, u64 basem, bool *idle) +{ + return __get_next_timer_interrupt(basej, basem, idle); } =20 /** --=20 2.39.2 From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A04ABC4167B for ; Fri, 1 Dec 2023 09:28:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378154AbjLAJ14 (ORCPT ); Fri, 1 Dec 2023 04:27:56 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54410 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378071AbjLAJ12 (ORCPT ); Fri, 1 Dec 2023 04:27:28 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CE00B173B for ; Fri, 1 Dec 2023 01:27:18 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422837; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=nS3of1gsjpadmlTzOeKtxhnS0y1kmX6N3aik41bHBiA=; b=jd8JdSo6RSMAzUQGD0eFZtqqXum4T5DNbkhKfHsGgfKrpZeYgvPMRbitqOvajGAVnOXjI6 CUwVNu95rNCy/L5GzK63NOh365EDVDrf9ayAK4msa7dXSpEa80xXUWomRi6duxWLFm+VbM qCr1hrcESNQGxbIdSVpGa6B5nMD7U+enDcqohqFlaqh/MYvEqE3lCzl2P2uDwny8GJ0pZb e+Y7Q5UkpxPIXt7kcmWi+U4AE9QBHs0PlQvwXPRBOBrT+RaB+0SEBxJG882s2281fx76As 0B3s31n61vB24z+VP0fxZkI3ZAtKnfsQ0JzpWsdc4wBnNvNXxSgu/bYlY0W5kw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422837; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=nS3of1gsjpadmlTzOeKtxhnS0y1kmX6N3aik41bHBiA=; b=XvAVoft42FnLB6t8nWzHoq+keWMNp0u+ZuAOQmacO5++zBupzj5qe3N+KJ0loGqLT7o1ZZ rrBvtWXBA6WYHMAg== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen Subject: [PATCH v9 16/32] timers: Optimization for timer_base_try_to_set_idle() Date: Fri, 1 Dec 2023 10:26:38 +0100 Message-Id: <20231201092654.34614-17-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" When tick is stopped also the timer base is_idle flag is set. When reentering the timer_base_try_to_set_idle() with the tick stopped, there is no need to check whether the timer base needs to be set idle again. When a timer was enqueued in the meantime, this is already handled by the nohz_get_next_event() call which was executed before tick_nohz_stop_tick(). Signed-off-by: Anna-Maria Behnsen --- v9: New, as this optimization was splitted from the patch before. --- kernel/time/tick-sched.c | 2 +- kernel/time/timer.c | 11 ++++++++--- 2 files changed, 9 insertions(+), 4 deletions(-) diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 3e1cdb7c6966..c6b415052c56 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -886,7 +886,7 @@ static void tick_nohz_stop_tick(struct tick_sched *ts, = int cpu) struct clock_event_device *dev =3D __this_cpu_read(tick_cpu_device.evtdev= ); unsigned long basejiff =3D ts->last_jiffies; u64 basemono =3D ts->timer_expires_base; - bool timer_idle; + bool timer_idle =3D ts->tick_stopped; u64 expires; =20 /* Make sure we won't be trying to stop it twice in a row. */ diff --git a/kernel/time/timer.c b/kernel/time/timer.c index df6558f62e6f..177bcde8a2c0 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -1996,13 +1996,18 @@ u64 get_next_timer_interrupt(unsigned long basej, u= 64 basem) * timer_base_try_to_set_idle() - Try to set the idle state of the timer b= ases * @basej: base time jiffies * @basem: base time clock monotonic - * @idle: pointer to store the value of timer_base->is_idle + * @idle: pointer to store the value of timer_base->is_idle on return; + * *idle contains the information whether tick was already stopped * - * Returns the tick aligned clock monotonic time of the next pending - * timer or KTIME_MAX if no timer is pending. + * Returns the tick aligned clock monotonic time of the next pending timer= or + * KTIME_MAX if no timer is pending. When tick was already stopped KTIME_M= AX is + * returned as well. */ u64 timer_base_try_to_set_idle(unsigned long basej, u64 basem, bool *idle) { + if (*idle) + return KTIME_MAX; + return __get_next_timer_interrupt(basej, basem, idle); } =20 --=20 2.39.2 From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 76002C4167B for ; Fri, 1 Dec 2023 09:28:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378087AbjLAJ2D (ORCPT ); Fri, 1 Dec 2023 04:28:03 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54450 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378092AbjLAJ13 (ORCPT ); Fri, 1 Dec 2023 04:27:29 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E43B9198E for ; Fri, 1 Dec 2023 01:27:19 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422838; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=2ndzPV+KTt0XzydVGeObWOLfmNe4sV+QpfiiUpyraAg=; b=DdWrzuSIaDLRs7yzIx91ENx015zY+Bmvcwzkws9SsYYR3IPive1ZN/YjvXz5AIRcb3lUQJ 1eaFD55Yp/84jZkuy4xRdsDKlqi5dUG53CUAHvUuV54SW87J2P5dxCDkXn3pw2SM+IHA+m oliEtTzAMLz+4sI8FKcuCJKbwTxCuIWJgldOAhjkWo/A9xAV+u20RPxcVr6+JQyO5/lN/N eHQB8YWgHLehL8GusjKbxBsc60KV3OMVRv5+KyaETXeoUXX9j4McyXCEaPkbXT+pAVneeI QIo8xmTScm772bnbBNl5nHwoqorRETkJKffNZ6f40vJ/4UY22exgyqwM/wyewQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422838; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=2ndzPV+KTt0XzydVGeObWOLfmNe4sV+QpfiiUpyraAg=; b=gEaTy8k+UeiLTYq8M4pK9aVOhsiw88tdR3F5jM7tqK3wQRMcl5vQgHp9XLAOw+1WTVDKxw WN8aKGqD4x3gUABw== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen Subject: [PATCH v9 17/32] timers: Introduce add_timer() variants which modify timer flags Date: Fri, 1 Dec 2023 10:26:39 +0100 Message-Id: <20231201092654.34614-18-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Timer might be used as pinned timer (using add_timer_on()) and later on as non pinned timers using add_timer(). When the NOHZ timer pull at expiry model is in place, TIMER_PINNED flag is required to be used whenever a timer needs to expire on a dedicated CPU. Flag must no be set, if expiration on a dedicated CPU is not required. add_timer_on()'s behavior will be changed during the preparation patches for the NOHZ timer pull at expiry model to unconditionally set TIMER_PINNED flag. To be able to reset/set the flag when queueing a timer, two variants of add_timer() are introduced. This is a preparatory patch and has no functional change. Signed-off-by: Anna-Maria Behnsen --- v9: Update documentation to match kernel-doc style (missing brackets after function names) New in v6 --- include/linux/timer.h | 2 ++ kernel/time/timer.c | 34 ++++++++++++++++++++++++++++++++++ 2 files changed, 36 insertions(+) diff --git a/include/linux/timer.h b/include/linux/timer.h index 26a545bb0153..404bb31a95c7 100644 --- a/include/linux/timer.h +++ b/include/linux/timer.h @@ -179,6 +179,8 @@ extern int timer_reduce(struct timer_list *timer, unsig= ned long expires); #define NEXT_TIMER_MAX_DELTA ((1UL << 30) - 1) =20 extern void add_timer(struct timer_list *timer); +extern void add_timer_local(struct timer_list *timer); +extern void add_timer_global(struct timer_list *timer); =20 extern int try_to_del_timer_sync(struct timer_list *timer); extern int timer_delete_sync(struct timer_list *timer); diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 177bcde8a2c0..0ce0e6b25482 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -1245,6 +1245,40 @@ void add_timer(struct timer_list *timer) } EXPORT_SYMBOL(add_timer); =20 +/** + * add_timer_local() - Start a timer on the local CPU + * @timer: The timer to be started + * + * Same as add_timer() except that the timer flag TIMER_PINNED is set. + * + * See add_timer() for further details. + */ +void add_timer_local(struct timer_list *timer) +{ + if (WARN_ON_ONCE(timer_pending(timer))) + return; + timer->flags |=3D TIMER_PINNED; + __mod_timer(timer, timer->expires, MOD_TIMER_NOTPENDING); +} +EXPORT_SYMBOL(add_timer_local); + +/** + * add_timer_global() - Start a timer without TIMER_PINNED flag set + * @timer: The timer to be started + * + * Same as add_timer() except that the timer flag TIMER_PINNED is unset. + * + * See add_timer() for further details. + */ +void add_timer_global(struct timer_list *timer) +{ + if (WARN_ON_ONCE(timer_pending(timer))) + return; + timer->flags &=3D ~TIMER_PINNED; + __mod_timer(timer, timer->expires, MOD_TIMER_NOTPENDING); +} +EXPORT_SYMBOL(add_timer_global); + /** * add_timer_on - Start a timer on a particular CPU * @timer: The timer to be started --=20 2.39.2 From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3615DC07E97 for ; Fri, 1 Dec 2023 09:28:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378128AbjLAJ2L (ORCPT ); Fri, 1 Dec 2023 04:28:11 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54362 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378110AbjLAJ1j (ORCPT ); Fri, 1 Dec 2023 04:27:39 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3A696199F for ; Fri, 1 Dec 2023 01:27:20 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422838; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=fQra51vM0+AF7Pw741oQBrBk7Zt04iCrGLsTZoJApiI=; b=N8IXtw37hnuRY5f/tQtu7mjNOGcU/i3xD1XD3YN/HcZkRvbEDJTCxJEnzHY59YsAQVlW09 M5V5N1Gaw3UDmlFJvd6Z3vXYCUSobPSzHupk7g2MtzfvPcf0yqMH0bkXkUO4BKdnWaaWag PfqxXUIVhTJ5BMnzCgx3VYAMPd+H+/KSwsWZN44BekJmTMFcHV0S4mjzW1xWSg8njws7ZS je0YZRUi4Hb2chqYKXYLxJo1xR7MWsuTgVXgZs6Gmn/tk8VTmsCEyYfpAlpj+s72ofJ+N+ 3u+B/K5EqYxi8Sxy6Nwv8i8Y0C4kuRCAJObBt669iC2PHpvmplNq5EJtRupBAg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422838; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=fQra51vM0+AF7Pw741oQBrBk7Zt04iCrGLsTZoJApiI=; b=R5Qn2IaGcKetkUnTnZUQoeXbKXVdaaPRJW0YVxJFh572/+9QYRhJ06YDFf7IlhLPVjNo0B I8kGucuTQGt9uwCw== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen , Tejun Heo , Lai Jiangshan Subject: [PATCH v9 18/32] workqueue: Use global variant for add_timer() Date: Fri, 1 Dec 2023 10:26:40 +0100 Message-Id: <20231201092654.34614-19-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" The implementation of the NOHZ pull at expiry model will change the timer bases per CPU. Timers, that have to expire on a specific CPU, require the TIMER_PINNED flag. If the CPU doesn't matter, the TIMER_PINNED flag must be dropped. This is required for call sites which use the timer alternately as pinned and not pinned timer like workqueues do. Therefore use add_timer_global() to make sure TIMER_PINNED flag is dropped. Signed-off-by: Anna-Maria Behnsen Reviewed-by: Frederic Weisbecker Acked-by: Tejun Heo Cc: Tejun Heo Cc: Lai Jiangshan --- v6: - New patch: As v6 provides unconditially setting TIMER_PINNED flag in add_timer_on() workqueue requires new add_timer_global() variant. --- kernel/workqueue.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 6e578f576a6f..3a1360794137 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1958,7 +1958,7 @@ static void __queue_delayed_work(int cpu, struct work= queue_struct *wq, if (unlikely(cpu !=3D WORK_CPU_UNBOUND)) add_timer_on(timer, cpu); else - add_timer(timer); + add_timer_global(timer); } =20 /** --=20 2.39.2 From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 520FDC4167B for ; Fri, 1 Dec 2023 09:28:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378215AbjLAJ2T (ORCPT ); Fri, 1 Dec 2023 04:28:19 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54420 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378145AbjLAJ1x (ORCPT ); Fri, 1 Dec 2023 04:27:53 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 94EEC19BA for ; Fri, 1 Dec 2023 01:27:21 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422840; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=1gYaVFuPoy5UW7Ox9DtRT+q6BrvDn/y7/UpgVZp13oQ=; b=PAq/TcXiBr3vZ/bkP9wgwgb+f+unPFLW+vAXzRt+6k89zhx2iT2ghtEO3DDzYolFQNZOSV Dca4vwfGYpZBDms4ilYjqB8hCoVv4jZuEZgU0QzHrKNk/pGZQgajCQo0/Aek2w1bmQfPC/ 5j4+ejwW8gzdI+22p3K0gko4dopIc4xJmfa4JJaKSzGLhapw4mozgr5/AE8c84BjKIWsFW +0VqVw+gdHK/+qHoLWNSRGcBUSLz/GJFhC9yJO/P42yvOvG6j1Jx5SEdqYP1ysDymvxjUo YmERn21/1bO1ajNJRbIUovB2JPf81tx2v0ls0z/9nr6Djonmo1rE3Eqao/xqcQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422840; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=1gYaVFuPoy5UW7Ox9DtRT+q6BrvDn/y7/UpgVZp13oQ=; b=CMqrDpwUb7eN+9HpKDodq8mpQY1W2MPkSZ2JjOUoBa5afMYeE9Fk/f8rGRM2JQgxmB4BPk YINYi1ThYLanF4CA== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen Subject: [PATCH v9 19/32] timers: add_timer_on(): Make sure TIMER_PINNED flag is set Date: Fri, 1 Dec 2023 10:26:41 +0100 Message-Id: <20231201092654.34614-20-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" When adding a timer to the timer wheel using add_timer_on(), it is an implicitly pinned timer. With the timer pull at expiry time model in place, TIMER_PINNED flag is required to make sure timers end up in proper base. Add TIMER_PINNED flag unconditionally when add_timer_on() is executed. Signed-off-by: Anna-Maria Behnsen Reviewed-by: Frederic Weisbecker --- kernel/time/timer.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 0ce0e6b25482..ea94479ee7e2 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -1284,7 +1284,10 @@ EXPORT_SYMBOL(add_timer_global); * @timer: The timer to be started * @cpu: The CPU to start it on * - * Same as add_timer() except that it starts the timer on the given CPU. + * Same as add_timer() except that it starts the timer on the given CPU and + * the TIMER_PINNED flag is set. When timer shouldn't be a pinned timer in + * the next round, add_timer_global() should be used instead as it unsets + * the TIMER_PINNED flag. * * See add_timer() for further details. */ @@ -1298,6 +1301,9 @@ void add_timer_on(struct timer_list *timer, int cpu) if (WARN_ON_ONCE(timer_pending(timer))) return; =20 + /* Make sure timer flags have TIMER_PINNED flag set */ + timer->flags |=3D TIMER_PINNED; + new_base =3D get_timer_cpu_base(timer->flags, cpu); =20 /* --=20 2.39.2 From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E9FA2C10F04 for ; Fri, 1 Dec 2023 09:28:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378038AbjLAJ2W (ORCPT ); Fri, 1 Dec 2023 04:28:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54410 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378144AbjLAJ1x (ORCPT ); Fri, 1 Dec 2023 04:27:53 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 49A161BC0 for ; Fri, 1 Dec 2023 01:27:22 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422840; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=HptRrZ5M792iqw/iN2UweCexRRIRvwfiQKQYLI/3wHc=; b=yTBAHA/pD9Zi3YxjUh/mQPwH80wDQzu4NBOMSc/YlI4oybqc9oa+avtTTMz8Kf+WValTlA dlgISBVCf286D9fbca7mOEhZHUF/fAFl+SrOGDRZtFGcwqMIAvDyHD2cBjo+ebBS1CLvEY BXKYL4sowwjTmrKc4/uWkT8jC/FBfRqYPQGcgHMkXH8GrcgMASx+z1ttb8dMp23D7Ifp86 dwNPYPaYfxtbVjvmKlyr213mfH7G4EKdLJTnLXs1a3ogr5IK4ts3I8LmE4F7Oh8nBih1j6 8/itFyFnOyam5q9D2UY7ueoJkVx4/vtYSK3ZE08jUy2PONXP1WmfA9cIoISLVw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422840; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=HptRrZ5M792iqw/iN2UweCexRRIRvwfiQKQYLI/3wHc=; b=L5L6rigwBQq2b2USGQ9rEjf9ZzpKMx4OAE8/3HInusvYXAisr+mmjXdoDjX4CVFp3WP+ma yfayh02N64lbiAAw== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen Subject: [PATCH v9 20/32] timers: Ease code in run_local_timers() Date: Fri, 1 Dec 2023 10:26:42 +0100 Message-Id: <20231201092654.34614-21-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" The logic for raising a softirq the way it is implemented right now, is readable for two timer bases. When increasing numbers of timer bases, code gets harder to read. With the introduction of the timer migration hierarchy, there will be three timer bases. Therefore ease the code. No functional change. Signed-off-by: Anna-Maria Behnsen Reviewed-by: Frederic Weisbecker --- v5: New patch to decrease patch size of follow up patches --- kernel/time/timer.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index ea94479ee7e2..b14d84f1fe50 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -2132,16 +2132,14 @@ static void run_local_timers(void) struct timer_base *base =3D this_cpu_ptr(&timer_bases[BASE_STD]); =20 hrtimer_run_queues(); - /* Raise the softirq only if required. */ - if (time_before(jiffies, base->next_expiry)) { - if (!IS_ENABLED(CONFIG_NO_HZ_COMMON)) - return; - /* CPU is awake, so check the deferrable base. */ - base++; - if (time_before(jiffies, base->next_expiry)) + + for (int i =3D 0; i < NR_BASES; i++, base++) { + /* Raise the softirq only if required. */ + if (time_after_eq(jiffies, base->next_expiry)) { + raise_softirq(TIMER_SOFTIRQ); return; + } } - raise_softirq(TIMER_SOFTIRQ); } =20 /* --=20 2.39.2 From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 76DAAC4167B for ; Fri, 1 Dec 2023 09:28:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378092AbjLAJ2Z (ORCPT ); Fri, 1 Dec 2023 04:28:25 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46428 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378151AbjLAJ1y (ORCPT ); Fri, 1 Dec 2023 04:27:54 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E40561BC6 for ; Fri, 1 Dec 2023 01:27:22 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422841; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=j1C4FMe7pCnDmgmGqNMXsgIVbPWX+pQUl8aT2cvTpxE=; b=F20CyeVDuw7jm58dTRpNRqAbUkr6ff/ZKa8JWcMJjS1xEGOEeyHQaEWSIyjb9dtKsJPOl7 J51VieHtILw3lrPjVx/SxFIrkBv3xVrmzu018wirkiPPuCMkentQlQjSk0LX9NJeQXsS2a wiXf9rUilA3GKSDN/as4IYPlBFlBhTLb1VnnECsJcr8VK398l1Si0a67e1JFxOfsB7gxRw HGSINAF+Bw0YFNzOQTmLcxncwk05bTQmawg21ZZ8DFGSw+gUqURM0GR5+jlOxTabKjFv1s mMLPgavKnCIkKjeowAwjCsW9Xe46YZ1AfAWpO/dpgDEj8y0jJyegvsvCsPTEgw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422841; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=j1C4FMe7pCnDmgmGqNMXsgIVbPWX+pQUl8aT2cvTpxE=; b=zimkCzW5Hc5BNNqsTiWhrRNjS1Qz+YQP0rnArDywmOir6z0bmDO27jgmpr+TsxqqusG/PV rfRDRQ7UyL85FzDg== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen Subject: [PATCH v9 21/32] timers: Split next timer interrupt logic Date: Fri, 1 Dec 2023 10:26:43 +0100 Message-Id: <20231201092654.34614-22-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Logic for getting next timer interrupt (no matter of recalculated or already stored in base->next_expiry) is split into a separate function "next_timer_interrupt()" to make it available for new call sites. No functional change. Signed-off-by: Anna-Maria Behnsen --- v9: Adapt to the fix for empty timer bases. --- kernel/time/timer.c | 32 +++++++++++++++++++------------- 1 file changed, 19 insertions(+), 13 deletions(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index b14d84f1fe50..eda4972ca862 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -1951,12 +1951,29 @@ static u64 cmp_next_hrtimer_event(u64 basem, u64 ex= pires) return DIV_ROUND_UP_ULL(nextevt, TICK_NSEC) * TICK_NSEC; } =20 +static unsigned long next_timer_interrupt(struct timer_base *base, + unsigned long basej) +{ + if (base->next_expiry_recalc) + next_expiry_recalc(base); + + /* + * Move next_expiry for the empty base into the future to prevent a + * unnecessary raise of the timer softirq when the next_expiry value + * will be reached even if there is no timer pending. + */ + if (!base->timers_pending) + base->next_expiry =3D basej + NEXT_TIMER_MAX_DELTA; + + return base->next_expiry; +} + static inline u64 __get_next_timer_interrupt(unsigned long basej, u64 base= m, bool *idle) { struct timer_base *base =3D this_cpu_ptr(&timer_bases[BASE_STD]); - unsigned long nextevt =3D basej + NEXT_TIMER_MAX_DELTA; u64 expires =3D KTIME_MAX; + unsigned long nextevt; =20 /* * Pretend that there is no timer pending if the cpu is offline. @@ -1969,24 +1986,13 @@ static inline u64 __get_next_timer_interrupt(unsign= ed long basej, u64 basem, } =20 raw_spin_lock(&base->lock); - if (base->next_expiry_recalc) - next_expiry_recalc(base); + nextevt =3D next_timer_interrupt(base, basej); =20 if (base->timers_pending) { - nextevt =3D base->next_expiry; - /* If we missed a tick already, force 0 delta */ if (time_before(nextevt, basej)) nextevt =3D basej; expires =3D basem + (u64)(nextevt - basej) * TICK_NSEC; - } else { - /* - * Move next_expiry for the empty base into the future to - * prevent a unnecessary raise of the timer softirq when the - * next_expiry value will be reached even if there is no timer - * pending. - */ - base->next_expiry =3D nextevt; } =20 /* --=20 2.39.2 From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B4104C4167B for ; Fri, 1 Dec 2023 09:28:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378205AbjLAJ2g (ORCPT ); Fri, 1 Dec 2023 04:28:36 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46488 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378166AbjLAJ16 (ORCPT ); Fri, 1 Dec 2023 04:27:58 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8C2841BD1 for ; Fri, 1 Dec 2023 01:27:23 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422842; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=+2gcknKks11qfAlzDRSwTUEgmadWT0lIiDr7uy6c0kk=; b=LEMhqb0+RZ9Gahc8ukopEQMLtEPRI62P0m7xNOrYz0rhqfu+vWZo3RG2EukSZ+b4aILNJN Yt7OSurt0uLEc1ScjlC+583KJOOXDkZpgyuITxu/0HE7H6ZY1wdl4hIwJD8jLzv8LFe797 vrWwKxDyq9SNTbLfK4c8A+vfwHQEtEhwfgCGWHf8LcG3R84VSm93dQpSpDEBmc04ResOKE NGiZCg3KbbEMTPf+wYbgUa4qbpDoI4P5Ib/CjgYZ/aBidwJm1jF6MfNV1NiAPAoaOrO2eO Wx3EAMeQ+zJ6mrqwRL8qQW47qAPRiJ7HwhISN9FHOsnhCS5FmvfsfEhQTc/baA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422842; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=+2gcknKks11qfAlzDRSwTUEgmadWT0lIiDr7uy6c0kk=; b=M+AlmYf4Cp0yyTXzsnGSUkZHOjn1+YGbV8GtxZbglGJrFRSQu0jnF674YBl3aeatoLgQQR V1wLFUJDfAwiRHBQ== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen , Richard Cochran Subject: [PATCH v9 22/32] timers: Keep the pinned timers separate from the others Date: Fri, 1 Dec 2023 10:26:44 +0100 Message-Id: <20231201092654.34614-23-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Separate the storage space for pinned timers. Deferrable timers (doesn't matter if pinned or non pinned) are still enqueued into their own base. This is preparatory work for changing the NOHZ timer placement from a push at enqueue time to a pull at expiry time model. Originally-by: Richard Cochran (linutronix GmbH) Signed-off-by: Anna-Maria Behnsen Reviewed-by: Frederic Weisbecker --- v9: - Update was required (change of preceding patches) v6: - Drop set TIMER_PINNED flag in add_timer_on() and drop related warning. add_timer_on() fix is splitted into a separate patch. Therefore also drop "Reviewed-by" of Frederic Weisbecker v5: - Add WARN_ONCE() in add_timer_on() - Decrease patch size by splitting into three patches (this patch and the two before) v4: - split out logic to forward base clock into a helper function forward_base_clk() (Frederic) - ease the code in run_local_timers() and timer_clear_idle() (Frederic) --- kernel/time/timer.c | 95 ++++++++++++++++++++++++++++++++------------- 1 file changed, 68 insertions(+), 27 deletions(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index eda4972ca862..366ea26ce3ba 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -187,12 +187,18 @@ EXPORT_SYMBOL(jiffies_64); #define WHEEL_SIZE (LVL_SIZE * LVL_DEPTH) =20 #ifdef CONFIG_NO_HZ_COMMON -# define NR_BASES 2 -# define BASE_STD 0 -# define BASE_DEF 1 +/* + * If multiple bases need to be locked, use the base ordering for lock + * nesting, i.e. lowest number first. + */ +# define NR_BASES 3 +# define BASE_LOCAL 0 +# define BASE_GLOBAL 1 +# define BASE_DEF 2 #else # define NR_BASES 1 -# define BASE_STD 0 +# define BASE_LOCAL 0 +# define BASE_GLOBAL 0 # define BASE_DEF 0 #endif =20 @@ -899,7 +905,10 @@ static int detach_if_pending(struct timer_list *timer,= struct timer_base *base, =20 static inline struct timer_base *get_timer_cpu_base(u32 tflags, u32 cpu) { - struct timer_base *base =3D per_cpu_ptr(&timer_bases[BASE_STD], cpu); + int index =3D tflags & TIMER_PINNED ? BASE_LOCAL : BASE_GLOBAL; + struct timer_base *base; + + base =3D per_cpu_ptr(&timer_bases[index], cpu); =20 /* * If the timer is deferrable and NO_HZ_COMMON is set then we need @@ -912,7 +921,10 @@ static inline struct timer_base *get_timer_cpu_base(u3= 2 tflags, u32 cpu) =20 static inline struct timer_base *get_timer_this_cpu_base(u32 tflags) { - struct timer_base *base =3D this_cpu_ptr(&timer_bases[BASE_STD]); + int index =3D tflags & TIMER_PINNED ? BASE_LOCAL : BASE_GLOBAL; + struct timer_base *base; + + base =3D this_cpu_ptr(&timer_bases[index]); =20 /* * If the timer is deferrable and NO_HZ_COMMON is set then we need @@ -1971,9 +1983,10 @@ static unsigned long next_timer_interrupt(struct tim= er_base *base, static inline u64 __get_next_timer_interrupt(unsigned long basej, u64 base= m, bool *idle) { - struct timer_base *base =3D this_cpu_ptr(&timer_bases[BASE_STD]); + unsigned long nextevt, nextevt_local, nextevt_global; + struct timer_base *base_local, *base_global; u64 expires =3D KTIME_MAX; - unsigned long nextevt; + bool local_first; =20 /* * Pretend that there is no timer pending if the cpu is offline. @@ -1985,10 +1998,31 @@ static inline u64 __get_next_timer_interrupt(unsign= ed long basej, u64 basem, return expires; } =20 - raw_spin_lock(&base->lock); - nextevt =3D next_timer_interrupt(base, basej); + base_local =3D this_cpu_ptr(&timer_bases[BASE_LOCAL]); + base_global =3D this_cpu_ptr(&timer_bases[BASE_GLOBAL]); + + raw_spin_lock(&base_local->lock); + raw_spin_lock_nested(&base_global->lock, SINGLE_DEPTH_NESTING); + + nextevt_local =3D next_timer_interrupt(base_local, basej); + nextevt_global =3D next_timer_interrupt(base_global, basej); =20 - if (base->timers_pending) { + /* + * Check whether the local event is expiring before or at the same + * time as the global event. + * + * Note, that nextevt_global and nextevt_local might be based on + * different base->clk values. So it's not guaranteed that + * comparing with empty bases results in a correct local_first. + */ + if (base_local->timers_pending && base_global->timers_pending) + local_first =3D time_before_eq(nextevt_local, nextevt_global); + else + local_first =3D base_local->timers_pending; + + nextevt =3D local_first ? nextevt_local : nextevt_global; + + if (base_local->timers_pending || base_global->timers_pending) { /* If we missed a tick already, force 0 delta */ if (time_before(nextevt, basej)) nextevt =3D basej; @@ -1999,28 +2033,33 @@ static inline u64 __get_next_timer_interrupt(unsign= ed long basej, u64 basem, * We have a fresh next event. Check whether we can forward the * base. */ - __forward_timer_base(base, basej); + __forward_timer_base(base_local, basej); + __forward_timer_base(base_global, basej); =20 /* * Set base->is_idle only when caller is timer_base_try_to_set_idle() */ if (idle) { /* - * Base is idle if the next event is more than a tick away. + * Bases are idle if the next event is more than a tick away. * * If the base is marked idle then any timer add operation must * forward the base clk itself to keep granularity small. This - * idle logic is only maintained for the BASE_STD base, - * deferrable timers may still see large granularity skew (by - * design). + * idle logic is only maintained for the BASE_LOCAL and + * BASE_GLOBAL base, deferrable timers may still see large + * granularity skew (by design). */ - if (!base->is_idle) - base->is_idle =3D time_after(nextevt, basej + 1); - *idle =3D base->is_idle; - trace_timer_base_idle(base->is_idle, base->cpu); + if (!base_local->is_idle) { + bool is_idle =3D time_after(nextevt, basej + 1); + + base_local->is_idle =3D base_global->is_idle =3D is_idle; + } + *idle =3D base_local->is_idle; + trace_timer_base_idle(base_local->is_idle, base_local->cpu); } =20 - raw_spin_unlock(&base->lock); + raw_spin_unlock(&base_global->lock); + raw_spin_unlock(&base_local->lock); =20 return cmp_next_hrtimer_event(basem, expires); } @@ -2064,15 +2103,15 @@ u64 timer_base_try_to_set_idle(unsigned long basej,= u64 basem, bool *idle) */ void timer_clear_idle(void) { - struct timer_base *base =3D this_cpu_ptr(&timer_bases[BASE_STD]); - /* * We do this unlocked. The worst outcome is a remote enqueue sending * a pointless IPI, but taking the lock would just make the window for * sending the IPI a few instructions smaller for the cost of taking * the lock in the exit from idle path. */ - base->is_idle =3D false; + __this_cpu_write(timer_bases[BASE_LOCAL].is_idle, false); + __this_cpu_write(timer_bases[BASE_GLOBAL].is_idle, false); + trace_timer_base_idle(0, smp_processor_id()); } #endif @@ -2123,11 +2162,13 @@ static inline void __run_timers(struct timer_base *= base) */ static __latent_entropy void run_timer_softirq(struct softirq_action *h) { - struct timer_base *base =3D this_cpu_ptr(&timer_bases[BASE_STD]); + struct timer_base *base =3D this_cpu_ptr(&timer_bases[BASE_LOCAL]); =20 __run_timers(base); - if (IS_ENABLED(CONFIG_NO_HZ_COMMON)) + if (IS_ENABLED(CONFIG_NO_HZ_COMMON)) { + __run_timers(this_cpu_ptr(&timer_bases[BASE_GLOBAL])); __run_timers(this_cpu_ptr(&timer_bases[BASE_DEF])); + } } =20 /* @@ -2135,7 +2176,7 @@ static __latent_entropy void run_timer_softirq(struct= softirq_action *h) */ static void run_local_timers(void) { - struct timer_base *base =3D this_cpu_ptr(&timer_bases[BASE_STD]); + struct timer_base *base =3D this_cpu_ptr(&timer_bases[BASE_LOCAL]); =20 hrtimer_run_queues(); =20 --=20 2.39.2 From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5F8DFC4167B for ; Fri, 1 Dec 2023 09:28:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378173AbjLAJ2a (ORCPT ); Fri, 1 Dec 2023 04:28:30 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41224 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378167AbjLAJ16 (ORCPT ); Fri, 1 Dec 2023 04:27:58 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 439561BD6 for ; Fri, 1 Dec 2023 01:27:24 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422842; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=IdBDR0/tYNJhJm6cSGNxPr1uzJXFKTmkB6lItnLpMig=; b=3VH7dqj99SCQxtKQ1cSHqIAwzHimk0La70Y55WoifDDH6FVLlQTD7yElldyys8j5ak6Ljq YM2qwCAcIoxkO3hle8SiRG4mhPdiNBC/EL0AwtvgMX4Kqp1sbL/KJu9cLEaFC1rpO7xrQr D42gEzHFUKk9udutpeiMZHyEuXmMHcC/OsdsNl1AYyKkSb8mRAHkzDl6n6TU3xEWUhsY3K usjBau79n5bQPwp4uEWs/boCxqsThIyOccM08vg6aBAC9p8HXqfiG9EV+O2fxtx/1XSuGd 0lItm/ND1gNEZOUCslMqCpUE3+It9I2+8K80cO721GJVXTEDDgT7kZwG9JbByA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422842; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=IdBDR0/tYNJhJm6cSGNxPr1uzJXFKTmkB6lItnLpMig=; b=ObRXt5dMA2n4hQG6FSjAmMYBdk0L7rGzSvM/iGKlEi37gmbtj9rRCfhmDpjRCr0+YuSwYw jMbfdkMFH/57TNBQ== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen , Richard Cochran Subject: [PATCH v9 23/32] timers: Retrieve next expiry of pinned/non-pinned timers separately Date: Fri, 1 Dec 2023 10:26:45 +0100 Message-Id: <20231201092654.34614-24-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" For the conversion of the NOHZ timer placement to a pull at expiry time model it's required to have separate expiry times for the pinned and the non-pinned (movable) timers. Therefore struct timer_events is introduced. No functional change Originally-by: Richard Cochran (linutronix GmbH) Signed-off-by: Anna-Maria Behnsen Reviewed-by: Frederic Weisbecker --- v9: Update was required (change of preceding patches) --- kernel/time/timer.c | 35 +++++++++++++++++++++++++++++++---- 1 file changed, 31 insertions(+), 4 deletions(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 366ea26ce3ba..0d53d853ae22 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -221,6 +221,11 @@ struct timer_base { =20 static DEFINE_PER_CPU(struct timer_base, timer_bases[NR_BASES]); =20 +struct timer_events { + u64 local; + u64 global; +}; + #ifdef CONFIG_NO_HZ_COMMON =20 static DEFINE_STATIC_KEY_FALSE(timers_nohz_active); @@ -1983,10 +1988,11 @@ static unsigned long next_timer_interrupt(struct ti= mer_base *base, static inline u64 __get_next_timer_interrupt(unsigned long basej, u64 base= m, bool *idle) { + struct timer_events tevt =3D { .local =3D KTIME_MAX, .global =3D KTIME_MA= X }; unsigned long nextevt, nextevt_local, nextevt_global; struct timer_base *base_local, *base_global; - u64 expires =3D KTIME_MAX; bool local_first; + u64 expires; =20 /* * Pretend that there is no timer pending if the cpu is offline. @@ -1995,7 +2001,7 @@ static inline u64 __get_next_timer_interrupt(unsigned= long basej, u64 basem, if (cpu_is_offline(smp_processor_id())) { if (idle) *idle =3D true; - return expires; + return tevt.local; } =20 base_local =3D this_cpu_ptr(&timer_bases[BASE_LOCAL]); @@ -2022,13 +2028,31 @@ static inline u64 __get_next_timer_interrupt(unsign= ed long basej, u64 basem, =20 nextevt =3D local_first ? nextevt_local : nextevt_global; =20 - if (base_local->timers_pending || base_global->timers_pending) { + /* + * If the @nextevt is at max. one tick away, use @nextevt and store + * it in the local expiry value. The next global event is irrelevant in + * this case and can be left as KTIME_MAX. + */ + if (time_before_eq(nextevt, basej + 1)) { /* If we missed a tick already, force 0 delta */ if (time_before(nextevt, basej)) nextevt =3D basej; - expires =3D basem + (u64)(nextevt - basej) * TICK_NSEC; + tevt.local =3D basem + (u64)(nextevt - basej) * TICK_NSEC; + goto unlock; } =20 + /* + * Update tevt.* values: + * + * If the local queue expires first, then the global event can be + * ignored. If the global queue is empty, nothing to do either. + */ + if (!local_first && base_global->timers_pending) + tevt.global =3D basem + (u64)(nextevt_global - basej) * TICK_NSEC; + + if (base_local->timers_pending) + tevt.local =3D basem + (u64)(nextevt_local - basej) * TICK_NSEC; + /* * We have a fresh next event. Check whether we can forward the * base. @@ -2058,9 +2082,12 @@ static inline u64 __get_next_timer_interrupt(unsigne= d long basej, u64 basem, trace_timer_base_idle(base_local->is_idle, base_local->cpu); } =20 +unlock: raw_spin_unlock(&base_global->lock); raw_spin_unlock(&base_local->lock); =20 + expires =3D min_t(u64, tevt.local, tevt.global); + return cmp_next_hrtimer_event(basem, expires); } =20 --=20 2.39.2 From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 28DE1C4167B for ; Fri, 1 Dec 2023 09:28:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378057AbjLAJ2k (ORCPT ); Fri, 1 Dec 2023 04:28:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55022 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378025AbjLAJ2I (ORCPT ); Fri, 1 Dec 2023 04:28:08 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 530B51BE2 for ; Fri, 1 Dec 2023 01:27:25 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422843; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Uvz4yBwpNSi6fkT+oXIwoWMRBUwA4W1/FjhD6j61hx8=; b=qMsRwsr+tm2NABELd3xGyoIvs9Q3nKC7dA+P1bwnlmoDT+38yK2pUvPofS2GsHFXVt1295 HLaoAEa2mvXXxrwoBYDdvGli/++GZR+ZlkxXl6ewYb2ZbP77HoKfsEkiSiERJVGHfPUfkc sIvtIy0a3bwOVEnQVH/GBNHgGNiouQ70U2o+efM9AwjPrNKIXSnFQaQEn2QGhVLg+OwriT 86PuSupt2sL8tiDwd/TwQjJlybwK5x5Ya1ZGxjsBN4mZucPh9YxFI+GIi1FKFGgieAXDMv BAx2JlsD2U8C5nD8a1aLR8JCCNgq+5CP2wfh9Thj/lLlvXL2ISNL4GV0Go+zKw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422843; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Uvz4yBwpNSi6fkT+oXIwoWMRBUwA4W1/FjhD6j61hx8=; b=L2MRucXc33ide4+3K4Tl8jxU6vJKiCjEajaGrRk0LYhWnwHLfvl45rw41XC9DgrZmjhbtH ODBBm8bO2hjr5RAg== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen Subject: [PATCH v9 24/32] timers: Split out "get next timer interrupt" functionality Date: Fri, 1 Dec 2023 10:26:46 +0100 Message-Id: <20231201092654.34614-25-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" The functionality for getting the next timer interrupt in get_next_timer_interrupt() is split into a separate function fetch_next_timer_interrupt() to be usable by other call sites. This is preparatory work for the conversion of the NOHZ timer placement to a pull at expiry time model. No functional change. Signed-off-by: Anna-Maria Behnsen Reviewed-by: Frederic Weisbecker --- v9: Update was required (change of preceding patches) v6: s/splitted/split v5: Update commit message v4: Fix typo in comment --- kernel/time/timer.c | 64 +++++++++++++++++++++++++++------------------ 1 file changed, 38 insertions(+), 26 deletions(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 0d53d853ae22..fc376e06980e 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -1985,30 +1985,13 @@ static unsigned long next_timer_interrupt(struct ti= mer_base *base, return base->next_expiry; } =20 -static inline u64 __get_next_timer_interrupt(unsigned long basej, u64 base= m, - bool *idle) +static unsigned long fetch_next_timer_interrupt(unsigned long basej, u64 b= asem, + struct timer_base *base_local, + struct timer_base *base_global, + struct timer_events *tevt) { - struct timer_events tevt =3D { .local =3D KTIME_MAX, .global =3D KTIME_MA= X }; unsigned long nextevt, nextevt_local, nextevt_global; - struct timer_base *base_local, *base_global; bool local_first; - u64 expires; - - /* - * Pretend that there is no timer pending if the cpu is offline. - * Possible pending timers will be migrated later to an active cpu. - */ - if (cpu_is_offline(smp_processor_id())) { - if (idle) - *idle =3D true; - return tevt.local; - } - - base_local =3D this_cpu_ptr(&timer_bases[BASE_LOCAL]); - base_global =3D this_cpu_ptr(&timer_bases[BASE_GLOBAL]); - - raw_spin_lock(&base_local->lock); - raw_spin_lock_nested(&base_global->lock, SINGLE_DEPTH_NESTING); =20 nextevt_local =3D next_timer_interrupt(base_local, basej); nextevt_global =3D next_timer_interrupt(base_global, basej); @@ -2037,8 +2020,8 @@ static inline u64 __get_next_timer_interrupt(unsigned= long basej, u64 basem, /* If we missed a tick already, force 0 delta */ if (time_before(nextevt, basej)) nextevt =3D basej; - tevt.local =3D basem + (u64)(nextevt - basej) * TICK_NSEC; - goto unlock; + tevt->local =3D basem + (u64)(nextevt - basej) * TICK_NSEC; + return nextevt; } =20 /* @@ -2048,10 +2031,40 @@ static inline u64 __get_next_timer_interrupt(unsign= ed long basej, u64 basem, * ignored. If the global queue is empty, nothing to do either. */ if (!local_first && base_global->timers_pending) - tevt.global =3D basem + (u64)(nextevt_global - basej) * TICK_NSEC; + tevt->global =3D basem + (u64)(nextevt_global - basej) * TICK_NSEC; =20 if (base_local->timers_pending) - tevt.local =3D basem + (u64)(nextevt_local - basej) * TICK_NSEC; + tevt->local =3D basem + (u64)(nextevt_local - basej) * TICK_NSEC; + + return nextevt; +} + +static inline u64 __get_next_timer_interrupt(unsigned long basej, u64 base= m, + bool *idle) +{ + struct timer_events tevt =3D { .local =3D KTIME_MAX, .global =3D KTIME_MA= X }; + struct timer_base *base_local, *base_global; + unsigned long nextevt; + u64 expires; + + /* + * Pretend that there is no timer pending if the cpu is offline. + * Possible pending timers will be migrated later to an active cpu. + */ + if (cpu_is_offline(smp_processor_id())) { + if (idle) + *idle =3D true; + return tevt.local; + } + + base_local =3D this_cpu_ptr(&timer_bases[BASE_LOCAL]); + base_global =3D this_cpu_ptr(&timer_bases[BASE_GLOBAL]); + + raw_spin_lock(&base_local->lock); + raw_spin_lock_nested(&base_global->lock, SINGLE_DEPTH_NESTING); + + nextevt =3D fetch_next_timer_interrupt(basej, basem, base_local, + base_global, &tevt); =20 /* * We have a fresh next event. Check whether we can forward the @@ -2082,7 +2095,6 @@ static inline u64 __get_next_timer_interrupt(unsigned= long basej, u64 basem, trace_timer_base_idle(base_local->is_idle, base_local->cpu); } =20 -unlock: raw_spin_unlock(&base_global->lock); raw_spin_unlock(&base_local->lock); =20 --=20 2.39.2 From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8159BC4167B for ; Fri, 1 Dec 2023 09:28:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378133AbjLAJ2q (ORCPT ); Fri, 1 Dec 2023 04:28:46 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55030 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378171AbjLAJ2J (ORCPT ); Fri, 1 Dec 2023 04:28:09 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A2FF21BF0 for ; Fri, 1 Dec 2023 01:27:25 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422844; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=EMy/vrIt0wUl/L/Xwvre8ZwMi27M9d4t8qpR3rpCe2k=; b=yCIUgpS6DAyFZ8C+W8wpV+zk8mIstno8Qba+0sPG3PSxDJo+5BUB5F473xYkcVjgPP3dqD VXjM6gDKpd56m7SVWXJuVMkXwInZHcUxydH+gKyAWwMriE/h/7KF3lMYHr6DR5no3LxqaZ uu4OqVGV5fFmOBxfkTQvWy47cH74awVqLpGZjR2Mz+lCJ8ZQGLagORM4Agy4kf7/06VM/1 nBPTuvltdE2/XdGcl0pE/+sxVTES6ed2yHTYxln+d084ZGenBbqFLcyBExYdlxj2eDXZ+i aD8o5bbmJBzEW/BEvoH+717FWClTXFQVy1XfaCOY8yunMWNY7Mec/EXorOuv6w== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422844; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=EMy/vrIt0wUl/L/Xwvre8ZwMi27M9d4t8qpR3rpCe2k=; b=LwTgEJB/4Z47VOr90GUt4Dm/KDzYcbxGm3Lp9yeRN6wbMT0NGFec55NSe5xhWf9zfwsoL4 P0W4Qs23JbuKXoAQ== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen Subject: [PATCH v9 25/32] timers: Add get next timer interrupt functionality for remote CPUs Date: Fri, 1 Dec 2023 10:26:47 +0100 Message-Id: <20231201092654.34614-26-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" To prepare for the conversion of the NOHZ timer placement to a pull at expiry time model it's required to have functionality available getting the next timer interrupt on a remote CPU. Locking of the timer bases and getting the information for the next timer interrupt functionality is split into separate functions. This is required to be compliant with lock ordering when the new model is in place. Signed-off-by: Anna-Maria Behnsen Reviewed-by: Frederic Weisbecker --- v8: - Update comment v7: - Move functions into CONFIG_SMP && CONFIG_NO_HZ_COMMON section - change lock, fetch functions to be unconditional - split out unlock function into a separate function v6: - introduce timer_lock_remote_bases() to fix race --- kernel/time/tick-internal.h | 10 +++++ kernel/time/timer.c | 76 ++++++++++++++++++++++++++++++++++--- 2 files changed, 81 insertions(+), 5 deletions(-) diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h index dc12a938f00f..183ad32330fb 100644 --- a/kernel/time/tick-internal.h +++ b/kernel/time/tick-internal.h @@ -8,6 +8,11 @@ #include "timekeeping.h" #include "tick-sched.h" =20 +struct timer_events { + u64 local; + u64 global; +}; + #ifdef CONFIG_GENERIC_CLOCKEVENTS =20 # define TICK_DO_TIMER_NONE -1 @@ -155,6 +160,11 @@ extern unsigned long tick_nohz_active; extern void timers_update_nohz(void); # ifdef CONFIG_SMP extern struct static_key_false timers_migration_enabled; +extern void fetch_next_timer_interrupt_remote(unsigned long basej, u64 bas= em, + struct timer_events *tevt, + unsigned int cpu); +extern void timer_lock_remote_bases(unsigned int cpu); +extern void timer_unlock_remote_bases(unsigned int cpu); # endif #else /* CONFIG_NO_HZ_COMMON */ static inline void timers_update_nohz(void) { } diff --git a/kernel/time/timer.c b/kernel/time/timer.c index fc376e06980e..2cff43c10329 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -221,11 +221,6 @@ struct timer_base { =20 static DEFINE_PER_CPU(struct timer_base, timer_bases[NR_BASES]); =20 -struct timer_events { - u64 local; - u64 global; -}; - #ifdef CONFIG_NO_HZ_COMMON =20 static DEFINE_STATIC_KEY_FALSE(timers_nohz_active); @@ -2039,6 +2034,77 @@ static unsigned long fetch_next_timer_interrupt(unsi= gned long basej, u64 basem, return nextevt; } =20 +# ifdef CONFIG_SMP +/** + * fetch_next_timer_interrupt_remote() - Store next timers into @tevt + * @basej: base time jiffies + * @basem: base time clock monotonic + * @tevt: Pointer to the storage for the expiry values + * @cpu: Remote CPU + * + * Stores the next pending local and global timer expiry values in the + * struct pointed to by @tevt. If a queue is empty the corresponding + * field is set to KTIME_MAX. If local event expires before global + * event, global event is set to KTIME_MAX as well. + * + * Caller needs to make sure timer base locks are held (use + * timer_lock_remote_bases() for this purpose). + */ +void fetch_next_timer_interrupt_remote(unsigned long basej, u64 basem, + struct timer_events *tevt, + unsigned int cpu) +{ + struct timer_base *base_local, *base_global; + + /* Preset local / global events */ + tevt->local =3D tevt->global =3D KTIME_MAX; + + base_local =3D per_cpu_ptr(&timer_bases[BASE_LOCAL], cpu); + base_global =3D per_cpu_ptr(&timer_bases[BASE_GLOBAL], cpu); + + lockdep_assert_held(&base_local->lock); + lockdep_assert_held(&base_global->lock); + + fetch_next_timer_interrupt(basej, basem, base_local, base_global, tevt); +} + +/** + * timer_unlock_remote_bases - unlock timer bases of cpu + * @cpu: Remote CPU + * + * Unlocks the remote timer bases. + */ +void timer_unlock_remote_bases(unsigned int cpu) +{ + struct timer_base *base_local, *base_global; + + base_local =3D per_cpu_ptr(&timer_bases[BASE_LOCAL], cpu); + base_global =3D per_cpu_ptr(&timer_bases[BASE_GLOBAL], cpu); + + raw_spin_unlock(&base_global->lock); + raw_spin_unlock(&base_local->lock); +} + +/** + * timer_lock_remote_bases - lock timer bases of cpu + * @cpu: Remote CPU + * + * Locks the remote timer bases. + */ +void timer_lock_remote_bases(unsigned int cpu) +{ + struct timer_base *base_local, *base_global; + + base_local =3D per_cpu_ptr(&timer_bases[BASE_LOCAL], cpu); + base_global =3D per_cpu_ptr(&timer_bases[BASE_GLOBAL], cpu); + + lockdep_assert_irqs_disabled(); + + raw_spin_lock(&base_local->lock); + raw_spin_lock_nested(&base_global->lock, SINGLE_DEPTH_NESTING); +} +# endif /* CONFIG_SMP */ + static inline u64 __get_next_timer_interrupt(unsigned long basej, u64 base= m, bool *idle) { --=20 2.39.2 From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 16737C4167B for ; Fri, 1 Dec 2023 09:29:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378077AbjLAJ2y (ORCPT ); Fri, 1 Dec 2023 04:28:54 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50122 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378126AbjLAJ2K (ORCPT ); Fri, 1 Dec 2023 04:28:10 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BC6641BFE for ; Fri, 1 Dec 2023 01:27:26 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422844; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=bWHMK6r5kBUJ9iV8cP/TU68Vsy3sDvddkiKO4TwUZlc=; b=QMhs93p2ZCm6/MJxUMJdkxY/fBy9yYF7JUtsxSHtc9PYue8MZ0SoTHBdgGncOOxORk0ako vL2tnp0171mhN/4n/ReEYLl/a3R6Z/zdScU2QBslAWcu1KSe4vZ+h5iv0arm6+pF4t+FeB NjTheIExH1dDjaJXiRJsT4vg4FMpVT27Wiuihfby106yl2uG6MuiyJfHPXoRVnihspDN6Y SFZd19aQtV1uHqBTmaAUH80vC9KQsqfY6IqczyD0Sp+K85mgP6sQgx6Te5oltDezegw1H0 luV9XbDyrXLtx5BGc7S0R3jPEnug9EJnE2fhRH49c0HGea35EpV2UQ/Z1rlS9A== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422844; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=bWHMK6r5kBUJ9iV8cP/TU68Vsy3sDvddkiKO4TwUZlc=; b=xZTklOBzQvP69gCnFqvs8Dq2tLlMJcoPnlLizYK7DoNtiWj3CrGJ5Pba/DvLj/dMeYpxV6 VDw0ycerZCa3TDCQ== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , "Richard Cochran (linutronix GmbH)" , Anna-Maria Behnsen Subject: [PATCH v9 26/32] timers: Restructure internal locking Date: Fri, 1 Dec 2023 10:26:48 +0100 Message-Id: <20231201092654.34614-27-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: "Richard Cochran (linutronix GmbH)" Move the locking out from __run_timers() to the call sites, so the protected section can be extended at the call site. Preparatory patch for changing the NOHZ timer placement to a pull at expiry time model. No functional change. Signed-off-by: Richard Cochran (linutronix GmbH) Signed-off-by: Anna-Maria Behnsen --- kernel/time/timer.c | 31 +++++++++++++++++++++---------- 1 file changed, 21 insertions(+), 10 deletions(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 2cff43c10329..b0fa8afe9059 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -2230,11 +2230,7 @@ static inline void __run_timers(struct timer_base *b= ase) struct hlist_head heads[LVL_DEPTH]; int levels; =20 - if (time_before(jiffies, base->next_expiry)) - return; - - timer_base_lock_expiry(base); - raw_spin_lock_irq(&base->lock); + lockdep_assert_held(&base->lock); =20 while (time_after_eq(jiffies, base->clk) && time_after_eq(jiffies, base->next_expiry)) { @@ -2258,21 +2254,36 @@ static inline void __run_timers(struct timer_base *= base) while (levels--) expire_timers(base, heads + levels); } +} + +static void __run_timer_base(struct timer_base *base) +{ + if (time_before(jiffies, base->next_expiry)) + return; + + timer_base_lock_expiry(base); + raw_spin_lock_irq(&base->lock); + __run_timers(base); raw_spin_unlock_irq(&base->lock); timer_base_unlock_expiry(base); } =20 +static void run_timer_base(int index) +{ + struct timer_base *base =3D this_cpu_ptr(&timer_bases[index]); + + __run_timer_base(base); +} + /* * This function runs timers and the timer-tq in bottom half context. */ static __latent_entropy void run_timer_softirq(struct softirq_action *h) { - struct timer_base *base =3D this_cpu_ptr(&timer_bases[BASE_LOCAL]); - - __run_timers(base); + run_timer_base(BASE_LOCAL); if (IS_ENABLED(CONFIG_NO_HZ_COMMON)) { - __run_timers(this_cpu_ptr(&timer_bases[BASE_GLOBAL])); - __run_timers(this_cpu_ptr(&timer_bases[BASE_DEF])); + run_timer_base(BASE_GLOBAL); + run_timer_base(BASE_DEF); } } =20 --=20 2.39.2 From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 23159C4167B for ; Fri, 1 Dec 2023 09:28:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378256AbjLAJ2u (ORCPT ); Fri, 1 Dec 2023 04:28:50 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35886 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378045AbjLAJ2K (ORCPT ); Fri, 1 Dec 2023 04:28:10 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BDBB21FC3 for ; Fri, 1 Dec 2023 01:27:27 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422845; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=2bCi4tjY8tpa6/56LAAq7Ts1AT6CM22+SLDU0+3P94Q=; b=ahMjG98K3D4qOpghguU0ozTb5iyD0FeZ0e5qaVghe+bnsovvsp9OfHlCCOcSaqeATT2Vkh c1SjyHLSvCTPSGf11wOQ2zyxFpjVtFxMniVVw3F/Q52kHz0HrUtZlSBaE/xRYKYjhSSElS WxFViLi9vbKezJgTeWYLvyjOfEEJcuD9Tq0lrBkeaj4TP53vIdwFRvlg3MfeGjugPF8D06 +ybZr+fk81iM6Q8TgOKUYnWfazS4hFI6RmskRMMxWUfFwGZINJlsSbuAxriqyYib5oQAjk gi395JEUfMV5MhMhK8rJplN0PV51wsrhLxKt703ruRVq5tCXBavriNC/6VmjQg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422845; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=2bCi4tjY8tpa6/56LAAq7Ts1AT6CM22+SLDU0+3P94Q=; b=kRRyCgAuOmpklgvzYnSGwKqnsdjYnb8yb20cvQrna6iuwxMVhjGeLMMflSoErV8LCPv6EQ BP7JgzBcRXdMQuCA== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen Subject: [PATCH v9 27/32] timers: Check if timers base is handled already Date: Fri, 1 Dec 2023 10:26:49 +0100 Message-Id: <20231201092654.34614-28-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Due to the conversion of the NOHZ timer placement to a pull at expiry time model, the per CPU timer bases with non pinned timers are no longer handled only by the local CPU. In case a remote CPU already expires the non pinned timers base of the local cpu, nothing more needs to be done by the local CPU. A check at the begin of the expire timers routine is required, because timer base lock is dropped before executing the timer callback function. This is a preparatory work, but has no functional impact right now. Signed-off-by: Anna-Maria Behnsen --- v6: Drop double negation --- kernel/time/timer.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index b0fa8afe9059..a797603dfd49 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -2232,6 +2232,9 @@ static inline void __run_timers(struct timer_base *ba= se) =20 lockdep_assert_held(&base->lock); =20 + if (base->running_timer) + return; + while (time_after_eq(jiffies, base->clk) && time_after_eq(jiffies, base->next_expiry)) { levels =3D collect_expired_timers(base, heads); --=20 2.39.2 From nobody Mon Dec 29 03:02:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 442A4C4167B for ; Fri, 1 Dec 2023 09:29:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378032AbjLAJ25 (ORCPT ); Fri, 1 Dec 2023 04:28:57 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41282 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378182AbjLAJ2M (ORCPT ); Fri, 1 Dec 2023 04:28:12 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 17AF510F9 for ; Fri, 1 Dec 2023 01:27:27 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422846; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=eJA4rUNXEYpQORMvzo1itCOqghLSNPP1k7n+/ZfaqQw=; b=kEhWR6BpILpXBPleNuixEgrOHoHU+tSLpntkJXiwMC8Z3g/64p2VWGhRaqc+DO6Mn4EZt3 SO9QnO91MCwqCP4ALrC++C3NiTHGCv2Xj2yvjQiWf+xpDcizD47QTatabumYvok/s049QC Tz+T+2CbvsMSpwCdbPqfi5wVGiTaSj9thk/F3OpNgnFwDG4Vl09HX5UORn+Vz1m8M0spqJ 3HbiuMuItqnoTfzPiaP0bEMg1GB4c4GAs6osXO1jBr3jpHrsQaR2qP0WevQp63Mz1Z9o7M DymzebXlPg5BwTTWtHVUbz0zYCVu9+a2GQmWontxhQ9njwtYQ6QIra/RoFmvUQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422846; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=eJA4rUNXEYpQORMvzo1itCOqghLSNPP1k7n+/ZfaqQw=; b=PwBCPeViNGgkYRsSqSmBYt+Pw1wS+y9k7jm6ttbX8IIbrYXD4/2A5lmwrnK83nic0Y2ESy WLfgLJyWRc/AmGBA== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , "Richard Cochran (linutronix GmbH)" , Anna-Maria Behnsen Subject: [PATCH v9 28/32] tick/sched: Split out jiffies update helper function Date: Fri, 1 Dec 2023 10:26:50 +0100 Message-Id: <20231201092654.34614-29-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: "Richard Cochran (linutronix GmbH)" The logic to get the time of the last jiffies update will be needed by the timer pull model as well. Move the code into a global function in anticipation of the new caller. No functional change. Signed-off-by: Richard Cochran (linutronix GmbH) Signed-off-by: Anna-Maria Behnsen --- kernel/time/tick-internal.h | 1 + kernel/time/tick-sched.c | 18 +++++++++++++++--- 2 files changed, 16 insertions(+), 3 deletions(-) diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h index 183ad32330fb..e0e58dd18919 100644 --- a/kernel/time/tick-internal.h +++ b/kernel/time/tick-internal.h @@ -158,6 +158,7 @@ static inline void tick_nohz_init(void) { } #ifdef CONFIG_NO_HZ_COMMON extern unsigned long tick_nohz_active; extern void timers_update_nohz(void); +extern u64 get_jiffies_update(unsigned long *basej); # ifdef CONFIG_SMP extern struct static_key_false timers_migration_enabled; extern void fetch_next_timer_interrupt_remote(unsigned long basej, u64 bas= em, diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index c6b415052c56..aca0e133ba09 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -799,18 +799,30 @@ static inline bool local_timer_softirq_pending(void) return local_softirq_pending() & BIT(TIMER_SOFTIRQ); } =20 -static ktime_t tick_nohz_next_event(struct tick_sched *ts, int cpu) +/* + * Read jiffies and the time when jiffies were updated last + */ +u64 get_jiffies_update(unsigned long *basej) { - u64 basemono, next_tick, delta, expires; unsigned long basejiff; unsigned int seq; + u64 basemono; =20 - /* Read jiffies and the time when jiffies were updated last */ do { seq =3D read_seqcount_begin(&jiffies_seq); basemono =3D last_jiffies_update; basejiff =3D jiffies; } while (read_seqcount_retry(&jiffies_seq, seq)); + *basej =3D basejiff; + return basemono; +} + +static ktime_t tick_nohz_next_event(struct tick_sched *ts, int cpu) +{ + u64 basemono, next_tick, delta, expires; + unsigned long basejiff; + + basemono =3D get_jiffies_update(&basejiff); ts->last_jiffies =3D basejiff; ts->timer_expires_base =3D basemono; =20 --=20 2.39.2 From nobody Mon Dec 29 03:02:50 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BA480C4167B for ; Fri, 1 Dec 2023 09:29:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378247AbjLAJ3B (ORCPT ); Fri, 1 Dec 2023 04:29:01 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52290 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378081AbjLAJ2M (ORCPT ); Fri, 1 Dec 2023 04:28:12 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7FB571FCB for ; Fri, 1 Dec 2023 01:27:28 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422846; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Lz8mvggzvpUJEzbVXb4zUQlWwIeSFK/TCyXr++4TCPE=; b=EdTH1vhM3NGV6kmiUinGxLJ1Pm0M49zT313ppufUyWkX5Xlv7reO3Fk/sLVkQhQK7lDkKO OKyWIf49mKkvRSRvEz9LZ5jjWbVDcj8jaEtC5xYrxylR/wiK7coOeLfGlMNmNN21nXNxHf sLA55soY106JsKuC2y5XYkXpChswmiJF6O35gv4lDjmZE9ckO49OZq9IJPQgcUO9H2pjss N8ZOv+qp88KBvyM5BxqOCJu8mB64sQctsoqxBAJ1AjggNxBxfqRnfryYYOwsaBJgc3yW80 DJAqa12Niwukm8v9KHr9jy9njV6OEiO4TlibrrJzd9x+L3mFmztY9Gk/tbWvqg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422846; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Lz8mvggzvpUJEzbVXb4zUQlWwIeSFK/TCyXr++4TCPE=; b=7AWmEIidBRmfR/ZiDTR0IYKQlxe2r1jHuUlbpKg2IhmL9oFRBHb5oBeNAoamIAoHtCdXMK z8HthAkNaKBDp5Dg== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen Subject: [PATCH v9 29/32] timers: Introduce function to check timer base is_idle flag Date: Fri, 1 Dec 2023 10:26:51 +0100 Message-Id: <20231201092654.34614-30-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" To prepare for the conversion of the NOHZ timer placement to a pull at expiry time model it's required to have a function that returns the value of the is_idle flag of the timer base to keep the hierarchy states during online in sync with timer base state. No functional change. Signed-off-by: Anna-Maria Behnsen --- v9: new in v9 --- kernel/time/tick-internal.h | 1 + kernel/time/timer.c | 10 ++++++++++ 2 files changed, 11 insertions(+) diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h index e0e58dd18919..2d1a44850c20 100644 --- a/kernel/time/tick-internal.h +++ b/kernel/time/tick-internal.h @@ -166,6 +166,7 @@ extern void fetch_next_timer_interrupt_remote(unsigned = long basej, u64 basem, unsigned int cpu); extern void timer_lock_remote_bases(unsigned int cpu); extern void timer_unlock_remote_bases(unsigned int cpu); +extern bool timer_base_is_idle(void); # endif #else /* CONFIG_NO_HZ_COMMON */ static inline void timers_update_nohz(void) { } diff --git a/kernel/time/timer.c b/kernel/time/timer.c index a797603dfd49..b6c9ac0c3712 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -2201,6 +2201,16 @@ u64 timer_base_try_to_set_idle(unsigned long basej, = u64 basem, bool *idle) return __get_next_timer_interrupt(basej, basem, idle); } =20 +/** + * timer_base_is_idle() - Return whether timer base is set idle + * + * Returns value of local timer base is_idle value. + */ +bool timer_base_is_idle(void) +{ + return __this_cpu_read(timer_bases[BASE_LOCAL].is_idle); +} + /** * timer_clear_idle - Clear the idle state of the timer base * --=20 2.39.2 From nobody Mon Dec 29 03:02:50 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DF533C4167B for ; Fri, 1 Dec 2023 09:29:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378094AbjLAJ3U (ORCPT ); Fri, 1 Dec 2023 04:29:20 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46468 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378163AbjLAJ2T (ORCPT ); Fri, 1 Dec 2023 04:28:19 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 45CCC1FD5 for ; Fri, 1 Dec 2023 01:27:29 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422847; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=KXMsmyJyufEgL2ebmuiCg2SwPgKd/zMJW6cpMta/sXs=; b=wxVPUVtsCWsVS7pdkFzWxLvQMDp07QSFTczhOBOvCdH270RAdlV5leOboe7jXRZuz74+9w fMkcLwKKaNGJ9/JDiigBmL0BxJWjU2VjK/V7/TdO34VfbMWFXFm4BXNdzaPZr7fuWgO33y sS1gqbaag5+WNk3NJwM6JncYPt+1KVMLdswUTU/queLktc5xNyp7+pLvNfghdKkJST/tq1 dIMBEdMzp1SNJEMjJ4PDVMBqbl9FvQ/luCZEKs7SlCzB9VMzm/2/HEy8E60M2o+Q45ouTK 7tM9lraD9Hu1skZrsbiYl2Ow/nXNXrz1BhiwEJqSvXKPC8M1kf1Xryf2rIw2Qg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422847; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=KXMsmyJyufEgL2ebmuiCg2SwPgKd/zMJW6cpMta/sXs=; b=9YkZVZayylTHiBIfC+OG3OfnipCjB8b0mTo7ZpwtFl9tqvjKgWhB1wPbYXNbOCRQukQGWQ E0EwaDIELCZfjLDQ== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen Subject: [PATCH v9 30/32] timers: Implement the hierarchical pull model Date: Fri, 1 Dec 2023 10:26:52 +0100 Message-Id: <20231201092654.34614-31-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Placing timers at enqueue time on a target CPU based on dubious heuristics does not make any sense: 1) Most timer wheel timers are canceled or rearmed before they expire. 2) The heuristics to predict which CPU will be busy when the timer expires are wrong by definition. So placing the timers at enqueue wastes precious cycles. The proper solution to this problem is to always queue the timers on the local CPU and allow the non pinned timers to be pulled onto a busy CPU at expiry time. Therefore split the timer storage into local pinned and global timers: Local pinned timers are always expired on the CPU on which they have been queued. Global timers can be expired on any CPU. As long as a CPU is busy it expires both local and global timers. When a CPU goes idle it arms for the first expiring local timer. If the first expiring pinned (local) timer is before the first expiring movable timer, then no action is required because the CPU will wake up before the first movable timer expires. If the first expiring movable timer is before the first expiring pinned (local) timer, then this timer is queued into a idle timerqueue and eventually expired by some other active CPU. To avoid global locking the timerqueues are implemented as a hierarchy. The lowest level of the hierarchy holds the CPUs. The CPUs are associated to groups of 8, which are separated per node. If more than one CPU group exist, then a second level in the hierarchy collects the groups. Depending on the size of the system more than 2 levels are required. Each group has a "migrator" which checks the timerqueue during the tick for remote expirable timers. If the last CPU in a group goes idle it reports the first expiring event in the group up to the next group(s) in the hierarchy. If the last CPU goes idle it arms its timer for the first system wide expiring timer to ensure that no timer event is missed. Signed-off-by: Anna-Maria Behnsen --- v9: - Adapt to the changes of the preceding patches - Fix state inconsitency (when timer base is idle, cpu must also be marked as idle in hierarchy) - Make sure new timers are considered, when timer base is idle and a timer is enqueued into global queue (e.g. during interrupt) -> timer_use_tmigr() - Changes which are required due to the timer code change of marking the timer base idle in tick_nohz_stop_tick() v8: - Review of Frederic: - Fix hotplug race (introduction of wakeup_recalc) - Make wakeup and wakeup_recalc logic consistent all over the place - Fix child/group state race and read it with locks held - Add more clarifying comments - Fix grammar all over the place - change integers which act as boolean value into bool - rewrite condition in tmigr_check_migrator() without negation - Improve update events logic with a check of the first event - Implement a quick forecast which is called when get_next_timer_interrupt() is executed. v7: - Review remarks of Frederic and bigeasy: - change logic in tmigr_handle_remote_cpu() - s/kzalloc/kcalloc - move timer_expire_remote() into NO_HZ_COMMON && SMP config section - drop DBG_BUG_ON() makro and use only WARN_ON_ONCE() - remove leftovers from sibling logic during setup - Move timer_expire_remote() into tick-internal.h - Add documentation section about "Required event and timerqueue update after remote expiry" - Fix fallout of kernel test robot v6: - Fix typos - Review remarks of Peter Zijlstra (locking, struct member cleanup, use atomic_try_cmpxchg(), update struct member descriptions) - Fix race in tmigr_handle_remote_cpu() (Frederic Weisbecker) v5: - Review remarks of Frederic - Return nextevt when CPU is marked offline in timer migration hierarchy instead of KTIME_MAX - Fix update of group events issue, after remote expiring v4: - Fold typo fix in comment into proper patch "timer: Split out "get next timer interrupt" functionality" - Update wrong comment for tmigr_state union definition - Fix fallout of kernel test robot --- include/linux/cpuhotplug.h | 1 + kernel/time/Makefile | 3 + kernel/time/tick-internal.h | 1 + kernel/time/timer.c | 111 ++- kernel/time/timer_migration.c | 1636 +++++++++++++++++++++++++++++++++ kernel/time/timer_migration.h | 144 +++ 6 files changed, 1888 insertions(+), 8 deletions(-) create mode 100644 kernel/time/timer_migration.c create mode 100644 kernel/time/timer_migration.h diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h index efc0c0b07efb..85a78c5a7c01 100644 --- a/include/linux/cpuhotplug.h +++ b/include/linux/cpuhotplug.h @@ -245,6 +245,7 @@ enum cpuhp_state { CPUHP_AP_PERF_POWERPC_HV_24x7_ONLINE, CPUHP_AP_PERF_POWERPC_HV_GPCI_ONLINE, CPUHP_AP_PERF_CSKY_ONLINE, + CPUHP_AP_TMIGR_ONLINE, CPUHP_AP_WATCHDOG_ONLINE, CPUHP_AP_WORKQUEUE_ONLINE, CPUHP_AP_RANDOM_ONLINE, diff --git a/kernel/time/Makefile b/kernel/time/Makefile index 7e875e63ff3b..4af2a264a160 100644 --- a/kernel/time/Makefile +++ b/kernel/time/Makefile @@ -17,6 +17,9 @@ endif obj-$(CONFIG_GENERIC_SCHED_CLOCK) +=3D sched_clock.o obj-$(CONFIG_TICK_ONESHOT) +=3D tick-oneshot.o tick-sched.o obj-$(CONFIG_LEGACY_TIMER_TICK) +=3D tick-legacy.o +ifeq ($(CONFIG_SMP),y) + obj-$(CONFIG_NO_HZ_COMMON) +=3D timer_migration.o +endif obj-$(CONFIG_HAVE_GENERIC_VDSO) +=3D vsyscall.o obj-$(CONFIG_DEBUG_FS) +=3D timekeeping_debug.o obj-$(CONFIG_TEST_UDELAY) +=3D test_udelay.o diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h index 2d1a44850c20..9cec0c0c314f 100644 --- a/kernel/time/tick-internal.h +++ b/kernel/time/tick-internal.h @@ -167,6 +167,7 @@ extern void fetch_next_timer_interrupt_remote(unsigned = long basej, u64 basem, extern void timer_lock_remote_bases(unsigned int cpu); extern void timer_unlock_remote_bases(unsigned int cpu); extern bool timer_base_is_idle(void); +extern void timer_expire_remote(unsigned int cpu); # endif #else /* CONFIG_NO_HZ_COMMON */ static inline void timers_update_nohz(void) { } diff --git a/kernel/time/timer.c b/kernel/time/timer.c index b6c9ac0c3712..ac3e888d053f 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -53,6 +53,7 @@ #include =20 #include "tick-internal.h" +#include "timer_migration.h" =20 #define CREATE_TRACE_POINTS #include @@ -2103,6 +2104,64 @@ void timer_lock_remote_bases(unsigned int cpu) raw_spin_lock(&base_local->lock); raw_spin_lock_nested(&base_global->lock, SINGLE_DEPTH_NESTING); } + +static void __run_timer_base(struct timer_base *base); + +/** + * timer_expire_remote() - expire global timers of cpu + * @cpu: Remote CPU + * + * Expire timers of global base of remote CPU. + */ +void timer_expire_remote(unsigned int cpu) +{ + struct timer_base *base =3D per_cpu_ptr(&timer_bases[BASE_GLOBAL], cpu); + + __run_timer_base(base); +} + +static void timer_use_tmigr(unsigned long basej, u64 basem, + unsigned long *nextevt, bool *tick_stop_path, + bool timer_base_idle, struct timer_events *tevt) +{ + u64 next_tmigr; + + if (timer_base_idle) + next_tmigr =3D tmigr_cpu_new_timer(tevt->global); + else if (tick_stop_path) + next_tmigr =3D tmigr_cpu_deactivate(tevt->global); + else + next_tmigr =3D tmigr_quick_check(); + + /* + * If the CPU is the last going idle in timer migration hierarchy, make + * sure the CPU will wake up in time to handle remote timers. + * next_tmigr =3D=3D KTIME_MAX if other CPUs are still active. + */ + if (next_tmigr < tevt->local) { + u64 tmp; + + /* If we missed a tick already, force 0 delta */ + if (next_tmigr < basem) + next_tmigr =3D basem; + + tmp =3D div_u64(next_tmigr - basem, TICK_NSEC); + + *nextevt =3D basej + (unsigned long)tmp; + tevt->local =3D next_tmigr; + } +} +# else +static void timer_use_tmigr(unsigned long basej, u64 basem, + unsigned long *nextevt, bool *tick_stop_path, + bool timer_base_idle, struct timer_events *tevt) +{ + /* + * Make sure first event is written into tevt->local to not miss a + * timer on !SMP systems. + */ + tevt->local =3D min_t(u64, tevt->local, tevt->global); +} # endif /* CONFIG_SMP */ =20 static inline u64 __get_next_timer_interrupt(unsigned long basej, u64 base= m, @@ -2111,7 +2170,6 @@ static inline u64 __get_next_timer_interrupt(unsigned= long basej, u64 basem, struct timer_events tevt =3D { .local =3D KTIME_MAX, .global =3D KTIME_MA= X }; struct timer_base *base_local, *base_global; unsigned long nextevt; - u64 expires; =20 /* * Pretend that there is no timer pending if the cpu is offline. @@ -2132,6 +2190,21 @@ static inline u64 __get_next_timer_interrupt(unsigne= d long basej, u64 basem, nextevt =3D fetch_next_timer_interrupt(basej, basem, base_local, base_global, &tevt); =20 + /* + * When the when the next event is only one jiffie ahead there is no + * need to call timer migration hierarchy related + * functions. @tevt->global will be KTIME_MAX, nevertheless if the next + * timer is a global timer. This is also true, when the timer base is + * idle. + * + * The proper timer migration hierarchy function depends on the callsite + * and whether timer base is idle or not. @nextevt will be updated when + * this CPU needs to handle the first timer migration hierarchy event. + */ + if (time_after(nextevt, basej + 1)) + timer_use_tmigr(basej, basem, &nextevt, idle, + base_local->is_idle, &tevt); + /* * We have a fresh next event. Check whether we can forward the * base. @@ -2144,7 +2217,10 @@ static inline u64 __get_next_timer_interrupt(unsigne= d long basej, u64 basem, */ if (idle) { /* - * Bases are idle if the next event is more than a tick away. + * Bases are idle if the next event is more than a tick + * away. Caution: @nextevt could have changed by enqueueing a + * global timer into timer migration hierarchy. Therefore a new + * check is required here. * * If the base is marked idle then any timer add operation must * forward the base clk itself to keep granularity small. This @@ -2159,14 +2235,23 @@ static inline u64 __get_next_timer_interrupt(unsign= ed long basej, u64 basem, } *idle =3D base_local->is_idle; trace_timer_base_idle(base_local->is_idle, base_local->cpu); + + /* + * When timer base is not set idle, undo the effect of + * tmigr_cpu_deactivate() to prevent inconsitent states - active + * timer base but inactive timer migration hierarchy. + * + * When timer base was already marked idle, nothing will be + * changed here. + */ + if (!base_local->is_idle) + tmigr_cpu_activate(); } =20 raw_spin_unlock(&base_global->lock); raw_spin_unlock(&base_local->lock); =20 - expires =3D min_t(u64, tevt.local, tevt.global); - - return cmp_next_hrtimer_event(basem, expires); + return cmp_next_hrtimer_event(basem, tevt.local); } =20 /** @@ -2174,8 +2259,11 @@ static inline u64 __get_next_timer_interrupt(unsigne= d long basej, u64 basem, * @basej: base time jiffies * @basem: base time clock monotonic * - * Returns the tick aligned clock monotonic time of the next pending - * timer or KTIME_MAX if no timer is pending. + * Returns the tick aligned clock monotonic time of the next pending timer= or + * KTIME_MAX if no timer is pending. If timer of global base was queued in= to + * timer migration hierarchy, first global timer is not taken into account= . If + * it was the last CPU of timer migration hierarchy going idle, first glob= al + * event is taken into account. */ u64 get_next_timer_interrupt(unsigned long basej, u64 basem) { @@ -2228,6 +2316,9 @@ void timer_clear_idle(void) __this_cpu_write(timer_bases[BASE_GLOBAL].is_idle, false); =20 trace_timer_base_idle(0, smp_processor_id()); + + /* Activate without holding the timer_base->lock */ + tmigr_cpu_activate(); } #endif =20 @@ -2297,6 +2388,9 @@ static __latent_entropy void run_timer_softirq(struct= softirq_action *h) if (IS_ENABLED(CONFIG_NO_HZ_COMMON)) { run_timer_base(BASE_GLOBAL); run_timer_base(BASE_DEF); + + if (is_timers_nohz_active()) + tmigr_handle_remote(); } } =20 @@ -2311,7 +2405,8 @@ static void run_local_timers(void) =20 for (int i =3D 0; i < NR_BASES; i++, base++) { /* Raise the softirq only if required. */ - if (time_after_eq(jiffies, base->next_expiry)) { + if (time_after_eq(jiffies, base->next_expiry) || + (i =3D=3D BASE_DEF && tmigr_requires_handle_remote())) { raise_softirq(TIMER_SOFTIRQ); return; } diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c new file mode 100644 index 000000000000..05cd8f1bc45d --- /dev/null +++ b/kernel/time/timer_migration.c @@ -0,0 +1,1636 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Infrastructure for migratable timers + * + * Copyright(C) 2022 linutronix GmbH + */ +#include +#include +#include +#include +#include +#include + +#include "timer_migration.h" +#include "tick-internal.h" + +/* + * The timer migration mechanism is built on a hierarchy of groups. The + * lowest level group contains CPUs, the next level groups of CPU groups + * and so forth. The CPU groups are kept per node so for the normal case + * lock contention won't happen across nodes. Depending on the number of + * CPUs per node even the next level might be kept as groups of CPU groups + * per node and only the levels above cross the node topology. + * + * Example topology for a two node system with 24 CPUs each. + * + * LVL 2 [GRP2:0] + * GRP1:0 =3D GRP1:M + * + * LVL 1 [GRP1:0] [GRP1:1] + * GRP0:0 - GRP0:2 GRP0:3 - GRP0:5 + * + * LVL 0 [GRP0:0] [GRP0:1] [GRP0:2] [GRP0:3] [GRP0:4] [GRP0:5] + * CPUS 0-7 8-15 16-23 24-31 32-39 40-47 + * + * The groups hold a timer queue of events sorted by expiry time. These + * queues are updated when CPUs go in idle. When they come out of idle + * ignore flag of events is set. + * + * Each group has a designated migrator CPU/group as long as a CPU/group is + * active in the group. This designated role is necessary to avoid that all + * active CPUs in a group try to migrate expired timers from other CPUs, + * which would result in massive lock bouncing. + * + * When a CPU is awake, it checks in it's own timer tick the group + * hierarchy up to the point where it is assigned the migrator role or if + * no CPU is active, it also checks the groups where no migrator is set + * (TMIGR_NONE). + * + * If it finds expired timers in one of the group queues it pulls them over + * from the idle CPU and runs the timer function. After that it updates the + * group and the parent groups if required. + * + * CPUs which go idle arm their CPU local timer hardware for the next local + * (pinned) timer event. If the next migratable timer expires after the + * next local timer or the CPU has no migratable timer pending then the + * CPU does not queue an event in the LVL0 group. If the next migratable + * timer expires before the next local timer then the CPU queues that timer + * in the LVL0 group. In both cases the CPU marks itself idle in the LVL0 + * group. + * + * When CPU comes out of idle and when a group has at least a single active + * child, the ignore flag of the tmigr_event is set. This indicates, that + * the event is ignored even if it is still enqueued in the parent groups + * timer queue. It will be removed when touching the timer queue the next + * time. This spares locking in active path as the lock protects (after + * setup) only event information. For more information about locking, + * please read the section "Locking rules". + * + * If the CPU is the migrator of the group then it delegates that role to + * the next active CPU in the group or sets migrator to TMIGR_NONE when + * there is no active CPU in the group. This delegation needs to be + * propagated up the hierarchy so hand over from other leaves can happen at + * all hierarchy levels w/o doing a search. + * + * When the last CPU in the system goes idle, then it drops all migrator + * duties up to the top level of the hierarchy (LVL2 in the example). It + * then has to make sure, that it arms it's own local hardware timer for + * the earliest event in the system. + * + * + * Lifetime rules: + * --------------- + * + * The groups are built up at init time or when CPUs come online. They are + * not destroyed when a group becomes empty due to offlining. The group + * just won't participate in the hierarchy management anymore. Destroying + * groups would result in interesting race conditions which would just make + * the whole mechanism slow and complex. + * + * + * Locking rules: + * -------------- + * + * For setting up new groups and handling events it's required to lock both + * child and parent group. The lock ordering is always bottom up. This also + * includes the per CPU locks in struct tmigr_cpu. For updating the migrat= or and + * active CPU/group information atomic_try_cmpxchg() is used instead and o= nly + * the per CPU tmigr_cpu->lock is held. + * + * During the setup of groups tmigr_level_list is required. It is protecte= d by + * @tmigr_mutex. + * + * When @timer_base->lock as well as tmigr related locks are required, the= lock + * ordering is: first @timer_base->lock, afterwards tmigr related locks. + * + * + * Protection of the tmigr group state information: + * ------------------------------------------------ + * + * The state information with the list of active children and migrator nee= ds to + * be protected by a sequence counter. It prevents a race when updates in a + * child groups are propagated in changed order. The following scenario + * describes what happens without updating the sequence counter: + * + * Therefore, let's take three groups and four CPUs (CPU2 and CPU3 as well + * as GRP0:1 will not change during the scenario): + * + * LVL 1 [GRP1:0] + * migrator =3D GRP0:1 + * active =3D GRP0:0, GRP0:1 + * / \ + * LVL 0 [GRP0:0] [GRP0:1] + * migrator =3D CPU0 migrator =3D CPU2 + * active =3D CPU0 active =3D CPU2 + * / \ / \ + * CPUs 0 1 2 3 + * active idle active idle + * + * + * 1. CPU0 goes idle (changes are updated in GRP0:0; afterwards the current + * states of GRP0:0 and GRP1:0 are stored in the data for walking the + * hierarchy): + * + * LVL 1 [GRP1:0] + * migrator =3D GRP0:1 + * active =3D GRP0:0, GRP0:1 + * / \ + * LVL 0 [GRP0:0] [GRP0:1] + * --> migrator =3D TMIGR_NONE migrator =3D CPU2 + * --> active =3D active =3D CPU2 + * / \ / \ + * CPUs 0 1 2 3 + * --> idle idle active idle + * + * 2. CPU1 comes out of idle (changes are update in GRP0:0; afterwards the + * current states of GRP0:0 and GRP1:0 are stored in the data for walki= ng the + * hierarchy): + * + * LVL 1 [GRP1:0] + * migrator =3D GRP0:1 + * active =3D GRP0:0, GRP0:1 + * / \ + * LVL 0 [GRP0:0] [GRP0:1] + * --> migrator =3D CPU1 migrator =3D CPU2 + * --> active =3D CPU1 active =3D CPU2 + * / \ / \ + * CPUs 0 1 2 3 + * idle --> active active idle + * + * 3. Here comes the change of the order: Propagating the changes of step 2 + * through the hierarchy to GRP1:0 - nothing to be done, because GRP0:0 + * is already up to date. + * + * 4. Propagating the changes of step 1 through the hierarchy to GRP1:0 + * + * LVL 1 [GRP1:0] + * --> migrator =3D GRP0:1 + * --> active =3D GRP0:1 + * / \ + * LVL 0 [GRP0:0] [GRP0:1] + * migrator =3D CPU1 migrator =3D CPU2 + * active =3D CPU1 active =3D CPU2 + * / \ / \ + * CPUs 0 1 2 3 + * idle active active idle + * + * Now there is a inconsistent overall state because GRP0:0 is active, but + * it is marked as idle in the GRP1:0. This is prevented by incrementing + * sequence counter whenever changing the state. + * + * + * Required event and timerqueue update after a remote expiry: + * ----------------------------------------------------------- + * + * After a remote expiry of a CPU, a walk through the hierarchy updating t= he + * events and timerqueues has to be done when there is a 'new' global time= r of + * the remote CPU (which is obvious) but also if there is no new global ti= mer, + * but the remote CPU is still idle: + * + * 1. CPU2 is the migrator and does the remote expiry in GRP1:0; expiry of + * evt-CPU0 and evt-CPU1 are equal: + * + * LVL 1 [GRP1:0] + * migrator =3D GRP0:1 + * active =3D GRP0:1 + * --> timerqueue =3D evt-GRP0:0 + * / \ + * LVL 0 [GRP0:0] [GRP0:1] + * migrator =3D TMIGR_NONE migrator =3D CPU2 + * active =3D active =3D CPU2 + * groupevt.ignore =3D false groupevt.ignore =3D true + * groupevt.cpu =3D CPU0 groupevt.cpu =3D + * timerqueue =3D evt-CPU0, timerqueue =3D + * evt-CPU1 + * / \ / \ + * CPUs 0 1 2 3 + * idle idle active idle + * + * 2. Remove the first event of the timerqueue in GRP1:0 and expire the ti= mers + * of CPU0 (see evt-GRP0:0->cpu value): + * + * LVL 1 [GRP1:0] + * migrator =3D GRP0:1 + * active =3D GRP0:1 + * --> timerqueue =3D + * / \ + * LVL 0 [GRP0:0] [GRP0:1] + * migrator =3D TMIGR_NONE migrator =3D CPU2 + * active =3D active =3D CPU2 + * groupevt.ignore =3D false groupevt.ignore =3D true + * --> groupevt.cpu =3D CPU0 groupevt.cpu =3D + * timerqueue =3D evt-CPU0, timerqueue =3D + * evt-CPU1 + * / \ / \ + * CPUs 0 1 2 3 + * idle idle active idle + * + * 3. After the remote expiry CPU0 has no global timer that needs to be + * enqueued. When skipping the walk, the global timer of CPU1 is not ha= ndled, + * as the group event of GRP0:0 is not updated and not enqueued into GR= P1:0. The + * walk has to be done to update the group events and timerqueues: + * + * LVL 1 [GRP1:0] + * migrator =3D GRP0:1 + * active =3D GRP0:1 + * --> timerqueue =3D evt-GRP0:0 + * / \ + * LVL 0 [GRP0:0] [GRP0:1] + * migrator =3D TMIGR_NONE migrator =3D CPU2 + * active =3D active =3D CPU2 + * groupevt.ignore =3D false groupevt.ignore =3D true + * --> groupevt.cpu =3D CPU1 groupevt.cpu =3D + * --> timerqueue =3D evt-CPU1 timerqueue =3D + * / \ / \ + * CPUs 0 1 2 3 + * idle idle active idle + * + * Now CPU2 (migrator) is able to handle the timer of CPU1 as CPU2 only sc= ans + * the timerqueues of GRP0:1 and GRP1:0. + * + * The update of step 3 is valid to be skipped, when the remote CPU went o= ffline + * in the meantime because an update was already done during inactive path= . When + * CPU became active in the meantime, update isn't required as well, becau= se + * GRP0:0 is now longer idle. + */ + +static DEFINE_MUTEX(tmigr_mutex); +static struct list_head *tmigr_level_list __read_mostly; + +static unsigned int tmigr_hierarchy_levels __read_mostly; +static unsigned int tmigr_crossnode_level __read_mostly; + +static DEFINE_PER_CPU(struct tmigr_cpu, tmigr_cpu); + +#define TMIGR_NONE 0xFF +#define BIT_CNT 8 + +static inline bool tmigr_is_not_available(struct tmigr_cpu *tmc) +{ + return !(tmc->tmgroup && tmc->online); +} + +/* + * Returns true, when @childmask corresponds to the group migrator or when= the + * group is not active - so no migrator is set. + */ +static bool tmigr_check_migrator(struct tmigr_group *group, u8 childmask) +{ + union tmigr_state s; + + s.state =3D atomic_read(&group->migr_state); + + if ((s.migrator =3D=3D childmask) || (s.migrator =3D=3D TMIGR_NONE)) + return true; + + return false; +} + +static bool tmigr_check_migrator_and_lonely(struct tmigr_group *group, u8 = childmask) +{ + bool lonely, migrator =3D false; + unsigned long active; + union tmigr_state s; + + s.state =3D atomic_read(&group->migr_state); + + if ((s.migrator =3D=3D childmask) || (s.migrator =3D=3D TMIGR_NONE)) + migrator =3D true; + + active =3D s.active; + lonely =3D bitmap_weight(&active, BIT_CNT) <=3D 1; + + return (migrator && lonely); +} + +static bool tmigr_check_lonely(struct tmigr_group *group) +{ + unsigned long active; + union tmigr_state s; + + s.state =3D atomic_read(&group->migr_state); + + active =3D s.active; + + return bitmap_weight(&active, BIT_CNT) <=3D 1; +} + +typedef bool (*up_f)(struct tmigr_group *, struct tmigr_group *, void *); + +static void __walk_groups(up_f up, void *data, + struct tmigr_cpu *tmc) +{ + struct tmigr_group *child =3D NULL, *group =3D tmc->tmgroup; + + do { + WARN_ON_ONCE(group->level >=3D tmigr_hierarchy_levels); + + if (up(group, child, data)) + break; + + child =3D group; + group =3D group->parent; + } while (group); +} + +static void walk_groups(up_f up, void *data, struct tmigr_cpu *tmc) +{ + lockdep_assert_held(&tmc->lock); + + __walk_groups(up, data, tmc); +} + +/** + * struct tmigr_walk - data required for walking the hierarchy + * @evt: Pointer to tmigr_event which needs to be queued (of idle + * child group) + * @childmask: childmask of child group + * @nextexp: Next CPU event expiry information which is handed into + * the timer migration code by the timer code + * (get_next_timer_interrupt()); it is furthermore used for + * the first event which is queued, if the timer migration + * hierarchy is completely idle + * @childstate: tmigr_group->migr_state of the child - will be only + * reread when cmpxchg in the group fails (is required for + * the deactivate path and the new timer path) + * @groupstate: tmigr_group->migr_state of the group - will be only + * reread when cmpxchg in the group fails (is required for + * the active, the deactivate and the new timer path) + * @remote: Is set, when the new timer path is executed in + * tmigr_handle_remote_cpu() + */ +struct tmigr_walk { + struct tmigr_event *evt; + u8 childmask; + u64 nextexp; + union tmigr_state childstate; + union tmigr_state groupstate; + bool remote; +}; + +/** + * struct tmigr_remote_data - data required for remote expiry hierarchy wa= lk + * @basej: timer base in jiffies + * @now: timer base monotonic + * @nextexp: returns expiry of the first timer in the idle timer + * migration hierarchy to make sure the timer is handled in + * time; it is stored in the per CPU tmigr_cpu struct of + * CPU which expires remote timers + * @childmask: childmask of child group + * @check: is set if there is the need to handle remote timers; + * required in tmigr_check_handle_remote() only + * @tmc_active: this flag indicates, whether the CPU which triggers + * the hierarchy walk is !idle in the timer migration + * hierarchy. When the CPU is idle and the whole hierarchy is + * idle, only the first event of the top level has to be + * considered. + */ +struct tmigr_remote_data { + unsigned long basej; + u64 now; + u64 nextexp; + u8 childmask; + bool check; + bool tmc_active; +}; + +/* + * Returns the next event of the timerqueue @group->events + * + * Removes timers with ignore flag and update next_expiry of the group. Va= lues + * of the group event are updated in tmigr_update_events() only. + */ +static struct tmigr_event *tmigr_next_groupevt(struct tmigr_group *group) +{ + struct timerqueue_node *node =3D NULL; + struct tmigr_event *evt =3D NULL; + + lockdep_assert_held(&group->lock); + + WRITE_ONCE(group->next_expiry, KTIME_MAX); + + while ((node =3D timerqueue_getnext(&group->events))) { + evt =3D container_of(node, struct tmigr_event, nextevt); + + if (!evt->ignore) { + WRITE_ONCE(group->next_expiry, evt->nextevt.expires); + return evt; + } + + /* + * Remove next timers with ignore flag, because the group lock + * is held anyway + */ + if (!timerqueue_del(&group->events, node)) + break; + } + + return NULL; +} + +/* + * Return the next event which is already expired of the group timerqueue + * + * Event, which is returned, is also removed from the queue. + */ +static struct tmigr_event *tmigr_next_expired_groupevt(struct tmigr_group = *group, + u64 now) +{ + struct tmigr_event *evt =3D tmigr_next_groupevt(group); + + if (!evt || now < evt->nextevt.expires) + return NULL; + + /* + * The event is already expired. Remove it. If it's not the last event, + * then update all group event related information. + */ + if (timerqueue_del(&group->events, &evt->nextevt)) + tmigr_next_groupevt(group); + else + WRITE_ONCE(group->next_expiry, KTIME_MAX); + + return evt; +} + +static u64 tmigr_next_groupevt_expires(struct tmigr_group *group) +{ + struct tmigr_event *evt; + + evt =3D tmigr_next_groupevt(group); + + if (!evt) + return KTIME_MAX; + else + return evt->nextevt.expires; +} + +static bool tmigr_active_up(struct tmigr_group *group, + struct tmigr_group *child, + void *ptr) +{ + union tmigr_state curstate, newstate; + struct tmigr_walk *data =3D ptr; + bool walk_done; + u8 childmask; + + childmask =3D data->childmask; + newstate =3D curstate =3D data->groupstate; + +retry: + walk_done =3D true; + + if (newstate.migrator =3D=3D TMIGR_NONE) { + newstate.migrator =3D childmask; + + /* Changes need to be propagated */ + walk_done =3D false; + } + + newstate.active |=3D childmask; + + newstate.seq++; + + if (!atomic_try_cmpxchg(&group->migr_state, &curstate.state, newstate.sta= te)) { + newstate.state =3D curstate.state; + goto retry; + } + + if (group->parent && (walk_done =3D=3D false)) { + data->groupstate.state =3D atomic_read(&group->parent->migr_state); + data->childmask =3D group->childmask; + } + + /* + * The group is active and the event will be ignored - the ignore flag is + * updated without holding the lock. In case the bit is set while + * another CPU already handles remote events, nothing happens, because + * it is clear that the CPU became active just in this moment, or in + * worst case the event is handled remote. Nothing to worry about. + */ + group->groupevt.ignore =3D true; + + return walk_done; +} + +static void __tmigr_cpu_activate(struct tmigr_cpu *tmc) +{ + struct tmigr_walk data; + + data.childmask =3D tmc->childmask; + data.groupstate.state =3D atomic_read(&tmc->tmgroup->migr_state); + + tmc->cpuevt.ignore =3D true; + WRITE_ONCE(tmc->wakeup, KTIME_MAX); + tmc->wakeup_recalc =3D false; + + walk_groups(&tmigr_active_up, &data, tmc); +} + +/** + * tmigr_cpu_activate() - set this CPU active in timer migration hierarchy + * + * Call site timer_clear_idle() is called with interrupts disabled. + */ +void tmigr_cpu_activate(void) +{ + struct tmigr_cpu *tmc =3D this_cpu_ptr(&tmigr_cpu); + + if (tmigr_is_not_available(tmc)) + return; + + if (WARN_ON_ONCE(!tmc->idle)) + return; + + raw_spin_lock(&tmc->lock); + tmc->idle =3D false; + __tmigr_cpu_activate(tmc); + raw_spin_unlock(&tmc->lock); +} + +/* + * Returns true, if there is nothing to be propagated to the next level + * + * @data->nextexp is reset to KTIME_MAX; it is reused for the first global= event + * which needs to be handled by the migrator (in the top level group). + * + * This is the only place where the group event expiry value is set. + */ +static bool tmigr_update_events(struct tmigr_group *group, + struct tmigr_group *child, + struct tmigr_walk *data) +{ + struct tmigr_event *evt, *first_childevt; + bool walk_done, remote =3D data->remote; + bool leftmost_change =3D false; + u64 nextexp; + + if (child) { + raw_spin_lock(&child->lock); + raw_spin_lock_nested(&group->lock, SINGLE_DEPTH_NESTING); + + data->childstate.state =3D atomic_read(&child->migr_state); + data->groupstate.state =3D atomic_read(&group->migr_state); + + if (data->childstate.active) { + walk_done =3D true; + goto unlock; + } + + first_childevt =3D tmigr_next_groupevt(child); + nextexp =3D child->next_expiry; + evt =3D &child->groupevt; + } else { + nextexp =3D data->nextexp; + + /* + * Set @data->nextexp to KTIME_MAX; it is reused for the first + * global event which needs to be handled by the migrator (in + * the top level group). + */ + data->nextexp =3D KTIME_MAX; + + first_childevt =3D evt =3D data->evt; + + /* + * Walking the hierarchy is required in any case when a + * remote expiry was done before. This ensures to not lose + * already queued events in non active groups (see section + * "Required event and timerqueue update after remote + * expiry" in the documentation at the top). + * + * The two call sites which are executed without a remote expiry + * before, are not prevented from propagating changes through + * the hierarchy by the return: + * - When entering this path by tmigr_new_timer(), @evt->ignore + * is never set. + * - tmigr_inactive_up() takes care of the propagation by + * itself and ignores the return value. But an immediate + * return is required because nothing has to be done in this + * level as the event could be ignored. + */ + if (evt->ignore && !remote) + return true; + + raw_spin_lock(&group->lock); + data->groupstate.state =3D atomic_read(&group->migr_state); + } + + if (nextexp =3D=3D KTIME_MAX) { + evt->ignore =3D true; + + /* + * When the next child event could be ignored (nextexp is + * KTIME_MAX) and there was no remote timer handling before or + * the group is already active, there is no need to walk the + * hierarchy even if there is a parent group. + * + * The other way round: even if the event could be ignored, but + * if a remote timer handling was executed before and the group + * is not active, walking the hierarchy is required to not miss + * an enqueued timer in the non active group. The enqueued timer + * of the group needs to be propagated to a higher level to + * ensure it is handled. + */ + if (!remote || data->groupstate.active) { + walk_done =3D true; + goto unlock; + } + } else { + /* + * An update of @evt->cpu and @evt->ignore flag is required only + * when @child is set (the child is equal or higher than lvl0), + * but it doesn't matter if it is written once more to the per + * CPU event; make the update unconditional. + */ + evt->cpu =3D first_childevt->cpu; + evt->ignore =3D false; + } + + walk_done =3D !group->parent; + + /* + * If the child event is already queued in the group, remove it from the + * queue when the expiry time changed only. + */ + if (timerqueue_node_queued(&evt->nextevt)) { + if (evt->nextevt.expires =3D=3D nextexp) + goto check_toplvl; + + leftmost_change =3D timerqueue_getnext(&group->events) =3D=3D &evt->next= evt; + if (!timerqueue_del(&group->events, &evt->nextevt)) + WRITE_ONCE(group->next_expiry, KTIME_MAX); + } + + evt->nextevt.expires =3D nextexp; + + if (timerqueue_add(&group->events, &evt->nextevt)) { + leftmost_change =3D true; + WRITE_ONCE(group->next_expiry, nextexp); + } + +check_toplvl: + if (walk_done && (data->groupstate.migrator =3D=3D TMIGR_NONE)) { + /* + * Nothing to do when first event didn't changed and update was + * done during remote timer handling. + */ + if (remote && !leftmost_change) + goto unlock; + /* + * The top level group is idle and it has to be ensured the + * global timers are handled in time. (This could be optimized + * by keeping track of the last global scheduled event and only + * arming it on the CPU if the new event is earlier. Not sure if + * its worth the complexity.) + */ + data->nextexp =3D tmigr_next_groupevt_expires(group); + } + +unlock: + raw_spin_unlock(&group->lock); + + if (child) + raw_spin_unlock(&child->lock); + + return walk_done; +} + +static bool tmigr_new_timer_up(struct tmigr_group *group, + struct tmigr_group *child, + void *ptr) +{ + struct tmigr_walk *data =3D ptr; + + return tmigr_update_events(group, child, data); +} + +/* + * Returns the expiry of the next timer that needs to be handled. KTIME_MA= X is + * returned, when an active CPU will handle all the timer migration hierar= chy + * timers. + */ +static u64 tmigr_new_timer(struct tmigr_cpu *tmc, u64 nextexp) +{ + struct tmigr_walk data =3D { .evt =3D &tmc->cpuevt, + .nextexp =3D nextexp }; + + lockdep_assert_held(&tmc->lock); + + if (tmc->remote) + return KTIME_MAX; + + tmc->cpuevt.ignore =3D false; + data.remote =3D false; + + walk_groups(&tmigr_new_timer_up, &data, tmc); + + /* If there is a new first global event, make sure it is handled */ + return data.nextexp; +} + +static u64 tmigr_handle_remote_cpu(unsigned int cpu, u64 now, + unsigned long jif) +{ + struct timer_events tevt; + struct tmigr_walk data; + struct tmigr_cpu *tmc; + u64 next =3D KTIME_MAX; + + tmc =3D per_cpu_ptr(&tmigr_cpu, cpu); + + raw_spin_lock_irq(&tmc->lock); + + /* + * The remote CPU is offline or the CPU event does not has to be handled + * (the CPU is active or there is no longer an event to expire) or + * another CPU handles the CPU timers already or the next event was + * already expired - return! + */ + if (!tmc->online || tmc->remote || tmc->cpuevt.ignore || + now < tmc->cpuevt.nextevt.expires) { + raw_spin_unlock_irq(&tmc->lock); + return next; + } + + tmc->remote =3D true; + WRITE_ONCE(tmc->wakeup, KTIME_MAX); + + /* Drop the lock to allow the remote CPU to exit idle */ + raw_spin_unlock_irq(&tmc->lock); + + if (cpu !=3D smp_processor_id()) + timer_expire_remote(cpu); + + /* + * Lock ordering needs to be preserved - timer_base locks before tmigr + * related locks (see section "Locking rules" in the documentation at + * the top). During fetching the next timer interrupt, also tmc->lock + * needs to be held. Otherwise there is a possible race window against + * the CPU itself when it comes out of idle, updates the first timer in + * the hierarchy and goes back to idle. + * + * timer base locks are dropped as fast as possible: After checking + * whether the remote CPU went offline in the meantime and after + * fetching the next remote timer interrupt. Dropping the locks as fast + * as possible keeps the locking region small and prevents holding + * several (unnecessary) locks during walking the hierarchy for updating + * the timerqueue and group events. + */ + local_irq_disable(); + timer_lock_remote_bases(cpu); + raw_spin_lock(&tmc->lock); + + /* + * When the CPU went offline in the meantime, no hierarchy walk has to + * be done for updating the queued events, because the walk was + * already done during marking the CPU offline in the hierarchy. + * + * When the CPU is no longer idle, the CPU takes care of the timers and + * also of the timers in the path to the top. + * + * (See also section "Required event and timerqueue update after + * remote expiry" in the documentation at the top) + */ + if (!tmc->online || !tmc->idle) { + timer_unlock_remote_bases(cpu); + goto unlock; + } else { + /* next event of CPU */ + fetch_next_timer_interrupt_remote(jif, now, &tevt, cpu); + } + + timer_unlock_remote_bases(cpu); + + data.evt =3D &tmc->cpuevt; + data.nextexp =3D tevt.global; + data.remote =3D true; + + /* + * The update is done even when there is no 'new' global timer pending + * on the remote CPU (see section "Required event and timerqueue update + * after remote expiry" in the documentation at the top) + */ + walk_groups(&tmigr_new_timer_up, &data, tmc); + + next =3D data.nextexp; + +unlock: + tmc->remote =3D false; + raw_spin_unlock_irq(&tmc->lock); + + return next; +} + +static bool tmigr_handle_remote_up(struct tmigr_group *group, + struct tmigr_group *child, + void *ptr) +{ + struct tmigr_remote_data *data =3D ptr; + u64 now, next =3D KTIME_MAX; + struct tmigr_event *evt; + unsigned long jif; + u8 childmask; + + jif =3D data->basej; + now =3D data->now; + + childmask =3D data->childmask; + +again: + /* + * Handle the group only if @childmask is the migrator or if the + * group has no migrator. Otherwise the group is active and is + * handled by its own migrator. + */ + if (!tmigr_check_migrator(group, childmask)) + return true; + + raw_spin_lock_irq(&group->lock); + + evt =3D tmigr_next_expired_groupevt(group, now); + + if (evt) { + unsigned int remote_cpu =3D evt->cpu; + + raw_spin_unlock_irq(&group->lock); + + next =3D tmigr_handle_remote_cpu(remote_cpu, now, jif); + + /* check if there is another event, that needs to be handled */ + goto again; + } else { + raw_spin_unlock_irq(&group->lock); + } + + /* Update of childmask for the next level */ + data->childmask =3D group->childmask; + data->nextexp =3D next; + + return false; +} + +/** + * tmigr_handle_remote() - Handle global timers of remote idle CPUs + * + * Called from the timer soft interrupt with interrupts enabled. + */ +void tmigr_handle_remote(void) +{ + struct tmigr_cpu *tmc =3D this_cpu_ptr(&tmigr_cpu); + struct tmigr_remote_data data; + + if (tmigr_is_not_available(tmc)) + return; + + data.childmask =3D tmc->childmask; + data.nextexp =3D KTIME_MAX; + + /* + * NOTE: This is a doubled check because the migrator test will be done + * in tmigr_handle_remote_up() anyway. Keep this check to fasten the + * return when nothing has to be done. + */ + if (!tmigr_check_migrator(tmc->tmgroup, tmc->childmask)) + return; + + data.now =3D get_jiffies_update(&data.basej); + + /* + * Update @tmc->wakeup only at the end and do not reset @tmc->wakeup to + * KTIME_MAX. Even if tmc->lock is not held during the whole remote + * handling, tmc->wakeup is fine to be stale as it is called in + * interrupt context and tick_nohz_next_event() is executed in interrupt + * exit path only after processing the last pending interrupt. + */ + + __walk_groups(&tmigr_handle_remote_up, &data, tmc); + + raw_spin_lock_irq(&tmc->lock); + WRITE_ONCE(tmc->wakeup, data.nextexp); + raw_spin_unlock_irq(&tmc->lock); +} + +static bool tmigr_requires_handle_remote_up(struct tmigr_group *group, + struct tmigr_group *child, + void *ptr) +{ + struct tmigr_remote_data *data =3D ptr; + u8 childmask; + + childmask =3D data->childmask; + + /* + * Handle the group only if the child is the migrator or if the group + * has no migrator. Otherwise the group is active and is handled by its + * own migrator. + */ + if (!tmigr_check_migrator(group, childmask)) + return true; + + /* + * When there is a parent group and the CPU which triggered the + * hierarchy walk is not active, proceed the walk to reach the top level + * group before reading the next_expiry value. + */ + if (group->parent && !data->tmc_active) + goto out; + + /* + * On 32 bit systems the racy lockless check for next_expiry will + * turn into a random number generator. Therefore do the lockless + * check only on 64 bit systems. + */ + if (IS_ENABLED(CONFIG_64BIT)) { + data->nextexp =3D READ_ONCE(group->next_expiry); + if (data->now >=3D data->nextexp) { + data->check =3D true; + return true; + } + } else { + raw_spin_lock(&group->lock); + data->nextexp =3D group->next_expiry; + if (data->now >=3D group->next_expiry) { + data->check =3D true; + raw_spin_unlock(&group->lock); + return true; + } + raw_spin_unlock(&group->lock); + } + +out: + /* Update of childmask for the next level */ + data->childmask =3D group->childmask; + return false; +} + +/** + * tmigr_requires_handle_remote() - Check the need of remote timer handling + * + * Must be called with interrupts disabled. + */ +int tmigr_requires_handle_remote(void) +{ + struct tmigr_cpu *tmc =3D this_cpu_ptr(&tmigr_cpu); + struct tmigr_remote_data data; + unsigned int ret =3D 0; + unsigned long jif; + + if (tmigr_is_not_available(tmc)) + return ret; + + data.now =3D get_jiffies_update(&jif); + data.childmask =3D tmc->childmask; + data.nextexp =3D KTIME_MAX; + data.tmc_active =3D !tmc->idle; + data.check =3D false; + + /* + * When the CPU is active, walking the hierarchy to check whether a + * remote expiry is required. + * + * Check is done lockless as interrupts are disabled and @tmc->idle is + * set only by the local CPU. + */ + if (!tmc->idle) { + __walk_groups(&tmigr_requires_handle_remote_up, &data, tmc); + + if (data.nextexp !=3D KTIME_MAX) + ret =3D 1; + + return ret; + } + + /* + * When the CPU is idle, check whether the recalculation of @tmc->wakeup + * is required. @tmc->wakeup_recalc is set by a remote CPU which is + * about to go offline, was the last active CPU in the whole timer + * migration hierarchy and now delegates handling of the hierarchy to + * this CPU. + * + * Racy lockless check is valid: + * - @tmc->wakeup_recalc is set by the remote CPU before it issues + * reschedule IPI. + * - As interrupts are disabled here this CPU will either observe + * @tmc->wakeup_recalc set before the reschedule IPI can be handled or + * it will observe it when this function is called again on return + * from handling the reschedule IPI. + */ + if (tmc->wakeup_recalc) { + raw_spin_lock(&tmc->lock); + + __walk_groups(&tmigr_requires_handle_remote_up, &data, tmc); + + if (data.nextexp !=3D KTIME_MAX) + ret =3D 1; + + WRITE_ONCE(tmc->wakeup, data.nextexp); + tmc->wakeup_recalc =3D false; + raw_spin_unlock(&tmc->lock); + + return ret; + } + + /* + * When the CPU is idle and @tmc->wakeup is reliable, compare it with + * @data.now. On 64 bit it is valid to do this lockless. On 32 bit + * systems, holding the lock is required to get valid data on concurrent + * writers. + */ + if (IS_ENABLED(CONFIG_64BIT)) { + if (data.now >=3D READ_ONCE(tmc->wakeup)) + ret =3D 1; + } else { + raw_spin_lock(&tmc->lock); + if (data.now >=3D tmc->wakeup) + ret =3D 1; + raw_spin_unlock(&tmc->lock); + } + + return ret; +} + +/** + * tmigr_cpu_new_timer() - enqueue next global timer into hierarchy (idle = tmc) + * @nextexp: Next expiry of global timer (or KTIME_MAX if not) + * + * The CPU is already deactivated in the timer migration + * hierarchy. tick_nohz_get_sleep_length() calls tick_nohz_next_event() + * and thereby the timer idle path is executed once more. @tmc->wakeup + * holds the first timer, when the timer migration hierarchy is + * completely idle. + * + * Returns the first timer that needs to be handled by this CPU or KTIME_M= AX if + * nothing needs to be done. + */ +u64 tmigr_cpu_new_timer(u64 nextexp) +{ + struct tmigr_cpu *tmc =3D this_cpu_ptr(&tmigr_cpu); + u64 ret; + + if (tmigr_is_not_available(tmc)) + return nextexp; + + raw_spin_lock(&tmc->lock); + + ret =3D READ_ONCE(tmc->wakeup); + if (nextexp !=3D KTIME_MAX) { + if (nextexp !=3D tmc->cpuevt.nextevt.expires || + tmc->cpuevt.ignore) { + ret =3D tmigr_new_timer(tmc, nextexp); + } + } else if (tmc->wakeup_recalc) { + struct tmigr_remote_data data; + + data.now =3D KTIME_MAX; + data.childmask =3D tmc->childmask; + data.nextexp =3D KTIME_MAX; + data.tmc_active =3D false; + data.check =3D false; + + __walk_groups(&tmigr_requires_handle_remote_up, &data, tmc); + + ret =3D data.nextexp; + } + tmc->wakeup_recalc =3D false; + + /* + * Make sure the reevaluation of timers in idle path will not miss an + * event. + */ + WRITE_ONCE(tmc->wakeup, ret); + + raw_spin_unlock(&tmc->lock); + return ret; +} + +static bool tmigr_inactive_up(struct tmigr_group *group, + struct tmigr_group *child, + void *ptr) +{ + union tmigr_state curstate, newstate; + struct tmigr_walk *data =3D ptr; + bool walk_done; + u8 childmask; + + childmask =3D data->childmask; + newstate =3D curstate =3D data->groupstate; + +retry: + walk_done =3D true; + + /* Reset active bit when the child is no longer active */ + if (!data->childstate.active) + newstate.active &=3D ~childmask; + + if (newstate.migrator =3D=3D childmask) { + /* + * Find a new migrator for the group, because the child group is + * idle! + */ + if (!data->childstate.active) { + unsigned long new_migr_bit, active =3D newstate.active; + + new_migr_bit =3D find_first_bit(&active, BIT_CNT); + + if (new_migr_bit !=3D BIT_CNT) { + newstate.migrator =3D BIT(new_migr_bit); + } else { + newstate.migrator =3D TMIGR_NONE; + + /* Changes need to be propagated */ + walk_done =3D false; + } + } + } + + newstate.seq++; + + WARN_ON_ONCE((newstate.migrator !=3D TMIGR_NONE) && !(newstate.active)); + + if (!atomic_try_cmpxchg(&group->migr_state, &curstate.state, newstate.sta= te)) { + newstate.state =3D curstate.state; + + /* + * Something changed in the child/parent group in the meantime, + * reread the state of the child and parent; Update of + * data->childstate is required for event handling; + */ + if (child) + data->childstate.state =3D atomic_read(&child->migr_state); + + goto retry; + } + + data->groupstate =3D newstate; + data->remote =3D false; + + /* Event Handling */ + tmigr_update_events(group, child, data); + + if (group->parent && (walk_done =3D=3D false)) { + data->childmask =3D group->childmask; + data->childstate =3D newstate; + data->groupstate.state =3D atomic_read(&group->parent->migr_state); + } + + /* + * data->nextexp was set by tmigr_update_events() and contains the + * expiry of the first global event which needs to be handled + */ + if (data->nextexp !=3D KTIME_MAX) { + WARN_ON_ONCE(group->parent); + /* + * Top level path - If this CPU is about going offline, wake + * up some random other CPU so it will take over the + * migrator duty and program its timer properly. Ideally + * wake the CPU with the closest expiry time, but that's + * overkill to figure out. + * + * Set wakeup_recalc of remote CPU, to make sure the complete + * idle hierarchy with enqueued timers is reevaluated. + */ + if (!(this_cpu_ptr(&tmigr_cpu)->online)) { + struct tmigr_cpu *tmc =3D this_cpu_ptr(&tmigr_cpu); + unsigned int cpu =3D smp_processor_id(); + struct tmigr_cpu *tmc_resched; + + cpu =3D cpumask_any_but(cpu_online_mask, cpu); + tmc_resched =3D per_cpu_ptr(&tmigr_cpu, cpu); + + raw_spin_unlock(&tmc->lock); + + raw_spin_lock(&tmc_resched->lock); + tmc_resched->wakeup_recalc =3D true; + raw_spin_unlock(&tmc_resched->lock); + + raw_spin_lock(&tmc->lock); + smp_send_reschedule(cpu); + } + } + + return walk_done; +} + +static u64 __tmigr_cpu_deactivate(struct tmigr_cpu *tmc, u64 nextexp) +{ + struct tmigr_walk data =3D { .childmask =3D tmc->childmask, + .evt =3D &tmc->cpuevt, + .nextexp =3D nextexp, + .childstate.state =3D 0 }; + + data.groupstate.state =3D atomic_read(&tmc->tmgroup->migr_state); + + /* + * If nextexp is KTIME_MAX, the CPU event will be ignored because the + * local timer expires before the global timer, no global timer is set + * or CPU goes offline. + */ + if (nextexp !=3D KTIME_MAX) + tmc->cpuevt.ignore =3D false; + + walk_groups(&tmigr_inactive_up, &data, tmc); + return data.nextexp; +} + +/** + * tmigr_cpu_deactivate() - Put current CPU into inactive state + * @nextexp: The next timer event expiry set in the current CPU + * + * Must be called with interrupts disabled. + * + * Return: the next event expiry of the current CPU or the next event expi= ry + * from the hierarchy if this CPU is the top level migrator or the hierarc= hy is + * completely idle. + */ +u64 tmigr_cpu_deactivate(u64 nextexp) +{ + struct tmigr_cpu *tmc =3D this_cpu_ptr(&tmigr_cpu); + u64 ret; + + if (tmigr_is_not_available(tmc)) + return nextexp; + + raw_spin_lock(&tmc->lock); + + ret =3D __tmigr_cpu_deactivate(tmc, nextexp); + + tmc->idle =3D true; + + /* + * Make sure the reevaluation of timers in idle path will not miss an + * event. + */ + WRITE_ONCE(tmc->wakeup, ret); + + raw_spin_unlock(&tmc->lock); + return ret; +} + +/** + * tmigr_quick_check() - Quick forecast of next tmigr event when CPU wants= to + * go idle + * + * Returns KTIME_MAX, when it is probable that nothing has to be done (not= the + * only one in the level 0 group; and if it is the only one in level 0 gro= up, + * but there are more than a single group active in top level) + * + * Returns first expiry of the top level group, when it is the only one in= level + * 0 and top level also only has a single active child. + */ +u64 tmigr_quick_check(void) +{ + struct tmigr_cpu *tmc =3D this_cpu_ptr(&tmigr_cpu); + struct tmigr_group *topgroup; + struct list_head lvllist; + + if (tmigr_is_not_available(tmc)) + return KTIME_MAX; + + if (WARN_ON_ONCE(tmc->idle)) + return KTIME_MAX; + + if (!tmigr_check_migrator_and_lonely(tmc->tmgroup, tmc->childmask)) + return KTIME_MAX; + + for (int i =3D tmigr_hierarchy_levels; i > 0 ; i--) { + lvllist =3D tmigr_level_list[i - 1]; + if (list_is_singular(&lvllist)) { + topgroup =3D list_first_entry(&lvllist, struct tmigr_group, list); + + if (tmigr_check_lonely(topgroup)) + return READ_ONCE(topgroup->next_expiry); + } else { + continue; + } + } + + return KTIME_MAX; +} + +static void tmigr_init_group(struct tmigr_group *group, unsigned int lvl, + int node) +{ + union tmigr_state s; + + raw_spin_lock_init(&group->lock); + + group->level =3D lvl; + group->numa_node =3D lvl < tmigr_crossnode_level ? node : NUMA_NO_NODE; + + group->num_children =3D 0; + + s.migrator =3D TMIGR_NONE; + s.active =3D 0; + s.seq =3D 0; + atomic_set(&group->migr_state, s.state); + + timerqueue_init_head(&group->events); + timerqueue_init(&group->groupevt.nextevt); + group->groupevt.nextevt.expires =3D KTIME_MAX; + WRITE_ONCE(group->next_expiry, KTIME_MAX); + group->groupevt.ignore =3D true; +} + +static struct tmigr_group *tmigr_get_group(unsigned int cpu, int node, + unsigned int lvl) +{ + struct tmigr_group *tmp, *group =3D NULL; + + lockdep_assert_held(&tmigr_mutex); + + /* Try to attach to an existing group first */ + list_for_each_entry(tmp, &tmigr_level_list[lvl], list) { + /* + * If @lvl is below the cross numa node level, check whether + * this group belongs to the same numa node. + */ + if (lvl < tmigr_crossnode_level && tmp->numa_node !=3D node) + continue; + + /* Capacity left? */ + if (tmp->num_children >=3D TMIGR_CHILDREN_PER_GROUP) + continue; + + /* + * TODO: A possible further improvement: Make sure that all CPU + * siblings end up in the same group of the lowest level of the + * hierarchy. Rely on the topology sibling mask would be a + * reasonable solution. + */ + + group =3D tmp; + break; + } + + if (group) + return group; + + /* Allocate and set up a new group */ + group =3D kzalloc_node(sizeof(*group), GFP_KERNEL, node); + if (!group) + return ERR_PTR(-ENOMEM); + + tmigr_init_group(group, lvl, node); + + /* Setup successful. Add it to the hierarchy */ + list_add(&group->list, &tmigr_level_list[lvl]); + return group; +} + +static void tmigr_connect_child_parent(struct tmigr_group *child, + struct tmigr_group *parent) +{ + union tmigr_state childstate; + + raw_spin_lock_irq(&child->lock); + raw_spin_lock_nested(&parent->lock, SINGLE_DEPTH_NESTING); + + child->parent =3D parent; + child->childmask =3D BIT(parent->num_children++); + + raw_spin_unlock(&parent->lock); + raw_spin_unlock_irq(&child->lock); + + /* + * To prevent inconsistent states, active children need to be active in + * the new parent as well. Inactive children are already marked inactive + * in the parent group. + */ + childstate.state =3D atomic_read(&child->migr_state); + if (childstate.migrator !=3D TMIGR_NONE) { + struct tmigr_walk data; + + data.childmask =3D child->childmask; + data.groupstate.state =3D atomic_read(&parent->migr_state); + + /* + * There is only one new level per time. When connecting the + * child and the parent and set the child active when the parent + * is inactive, the parent needs to be the uppermost + * level. Otherwise there went something wrong! + */ + WARN_ON(!tmigr_active_up(parent, child, &data) && parent->parent); + } +} + +static int tmigr_setup_groups(unsigned int cpu, unsigned int node) +{ + struct tmigr_group *group, *child, **stack; + int top =3D 0, err =3D 0, i =3D 0; + struct list_head *lvllist; + + stack =3D kcalloc(tmigr_hierarchy_levels, sizeof(*stack), GFP_KERNEL); + if (!stack) + return -ENOMEM; + + do { + group =3D tmigr_get_group(cpu, node, i); + if (IS_ERR(group)) { + err =3D PTR_ERR(group); + break; + } + + top =3D i; + stack[i++] =3D group; + + /* + * When booting only less CPUs of a system than CPUs are + * available, not all calculated hierarchy levels are required. + * + * The loop is aborted as soon as the highest level, which might + * be different from tmigr_hierarchy_levels, contains only a + * single group. + */ + if (group->parent || i =3D=3D tmigr_hierarchy_levels || + (list_empty(&tmigr_level_list[i]) && + list_is_singular(&tmigr_level_list[i - 1]))) + break; + + } while (i < tmigr_hierarchy_levels); + + do { + group =3D stack[--i]; + + if (err < 0) { + list_del(&group->list); + kfree(group); + continue; + } + + WARN_ON_ONCE(i !=3D group->level); + + /* + * Update tmc -> group / child -> group connection + */ + if (i =3D=3D 0) { + struct tmigr_cpu *tmc =3D this_cpu_ptr(&tmigr_cpu); + + raw_spin_lock_irq(&group->lock); + + tmc->tmgroup =3D group; + tmc->childmask =3D BIT(group->num_children++); + + raw_spin_unlock_irq(&group->lock); + + /* There are no children that need to be connected */ + continue; + } else { + child =3D stack[i - 1]; + tmigr_connect_child_parent(child, group); + } + + /* check if uppermost level was newly created */ + if (top !=3D i) + continue; + + WARN_ON_ONCE(top =3D=3D 0); + + lvllist =3D &tmigr_level_list[top]; + if (group->num_children =3D=3D 1 && list_is_singular(lvllist)) { + lvllist =3D &tmigr_level_list[top - 1]; + list_for_each_entry(child, lvllist, list) { + if (child->parent) + continue; + + tmigr_connect_child_parent(child, group); + } + } + } while (i > 0); + + kfree(stack); + + return err; +} + +static int tmigr_add_cpu(unsigned int cpu) +{ + int node =3D cpu_to_node(cpu); + int ret; + + mutex_lock(&tmigr_mutex); + ret =3D tmigr_setup_groups(cpu, node); + mutex_unlock(&tmigr_mutex); + + return ret; +} + +static int tmigr_cpu_online(unsigned int cpu) +{ + struct tmigr_cpu *tmc =3D this_cpu_ptr(&tmigr_cpu); + unsigned int ret; + + /* First online attempt? Initialize CPU data */ + if (!tmc->tmgroup) { + raw_spin_lock_init(&tmc->lock); + + ret =3D tmigr_add_cpu(cpu); + if (ret < 0) + return ret; + + if (tmc->childmask =3D=3D 0) + return -EINVAL; + + timerqueue_init(&tmc->cpuevt.nextevt); + tmc->cpuevt.nextevt.expires =3D KTIME_MAX; + tmc->cpuevt.ignore =3D true; + tmc->cpuevt.cpu =3D cpu; + + tmc->remote =3D false; + WRITE_ONCE(tmc->wakeup, KTIME_MAX); + } + raw_spin_lock_irq(&tmc->lock); + if (timer_base_is_idle()) + tmc->idle =3D true; + else + __tmigr_cpu_activate(tmc); + tmc->online =3D true; + raw_spin_unlock_irq(&tmc->lock); + return 0; +} + +static int tmigr_cpu_offline(unsigned int cpu) +{ + struct tmigr_cpu *tmc =3D this_cpu_ptr(&tmigr_cpu); + + raw_spin_lock_irq(&tmc->lock); + tmc->online =3D false; + WRITE_ONCE(tmc->wakeup, KTIME_MAX); + + /* + * CPU has to handle the local events on his own, when on the way to + * offline; Therefore nextevt value is set to KTIME_MAX + */ + __tmigr_cpu_deactivate(tmc, KTIME_MAX); + raw_spin_unlock_irq(&tmc->lock); + + return 0; +} + +static int __init tmigr_init(void) +{ + unsigned int cpulvl, nodelvl, cpus_per_node, i; + unsigned int nnodes =3D num_possible_nodes(); + unsigned int ncpus =3D num_possible_cpus(); + int ret =3D -ENOMEM; + + /* Nothing to do if running on UP */ + if (ncpus =3D=3D 1) + return 0; + + /* + * Calculate the required hierarchy levels. Unfortunately there is no + * reliable information available, unless all possible CPUs have been + * brought up and all numa nodes are populated. + * + * Estimate the number of levels with the number of possible nodes and + * the number of possible CPUs. Assume CPUs are spread evenly across + * nodes. We cannot rely on cpumask_of_node() because there only already + * online CPUs are considered. + */ + cpus_per_node =3D DIV_ROUND_UP(ncpus, nnodes); + + /* Calc the hierarchy levels required to hold the CPUs of a node */ + cpulvl =3D DIV_ROUND_UP(order_base_2(cpus_per_node), + ilog2(TMIGR_CHILDREN_PER_GROUP)); + + /* Calculate the extra levels to connect all nodes */ + nodelvl =3D DIV_ROUND_UP(order_base_2(nnodes), + ilog2(TMIGR_CHILDREN_PER_GROUP)); + + tmigr_hierarchy_levels =3D cpulvl + nodelvl; + + /* + * If a numa node spawns more than one CPU level group then the next + * level(s) of the hierarchy contains groups which handle all CPU groups + * of the same numa node. The level above goes across numa nodes. Store + * this information for the setup code to decide when node matching is + * not longer required. + */ + tmigr_crossnode_level =3D cpulvl; + + tmigr_level_list =3D kcalloc(tmigr_hierarchy_levels, sizeof(struct list_h= ead), GFP_KERNEL); + if (!tmigr_level_list) + goto err; + + for (i =3D 0; i < tmigr_hierarchy_levels; i++) + INIT_LIST_HEAD(&tmigr_level_list[i]); + + pr_info("Timer migration: %d hierarchy levels; %d children per group;" + " %d crossnode level\n", + tmigr_hierarchy_levels, TMIGR_CHILDREN_PER_GROUP, + tmigr_crossnode_level); + + ret =3D cpuhp_setup_state(CPUHP_AP_TMIGR_ONLINE, "tmigr:online", + tmigr_cpu_online, tmigr_cpu_offline); + if (ret) + goto err; + + return 0; + +err: + pr_err("Timer migration setup failed\n"); + return ret; +} +late_initcall(tmigr_init); diff --git a/kernel/time/timer_migration.h b/kernel/time/timer_migration.h new file mode 100644 index 000000000000..260b87e5708d --- /dev/null +++ b/kernel/time/timer_migration.h @@ -0,0 +1,144 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +#ifndef _KERNEL_TIME_MIGRATION_H +#define _KERNEL_TIME_MIGRATION_H + +/* Per group capacity. Must be a power of 2! */ +#define TMIGR_CHILDREN_PER_GROUP 8 + +/** + * struct tmigr_event - a timer event associated to a CPU + * @nextevt: The node to enqueue an event in the parent group queue + * @cpu: The CPU to which this event belongs + * @ignore: Hint whether the event could be ignored; it is set when + * CPU or group is active; + */ +struct tmigr_event { + struct timerqueue_node nextevt; + unsigned int cpu; + bool ignore; +}; + +/** + * struct tmigr_group - timer migration hierarchy group + * @lock: Lock protecting the event information and group hierarchy + * information during setup + * @migr_state: State of the group (see union tmigr_state) + * @parent: Pointer to the parent group + * @groupevt: Next event of the group which is only used when the + * group is !active. The group event is then queued into + * the parent timer queue. + * Ignore bit of @groupevt is set when the group is active. + * @next_expiry: Base monotonic expiry time of the next event of the + * group; It is used for the racy lockless check whether a + * remote expiry is required; it is always reliable + * @events: Timer queue for child events queued in the group + * @childmask: childmask of the group in the parent group; is set + * during setup and will never change; could be read + * lockless + * @level: Hierarchy level of the group; Required during setup + * @list: List head that is added to the per level + * tmigr_level_list; is required during setup when a + * new group needs to be connected to the existing + * hierarchy groups + * @numa_node: Is set to numa node when level < tmigr_crossnode_level; + * otherwise it is set to NUMA_NO_NODE; Required for + * setup only to make sure CPUs and groups are per + * numa node as long as level < tmigr_crossnode_level + * @num_children: Counter of group children to make sure the group is only + * filled with TMIGR_CHILDREN_PER_GROUP; Required for setup + * only + */ +struct tmigr_group { + raw_spinlock_t lock; + atomic_t migr_state; + struct tmigr_group *parent; + struct tmigr_event groupevt; + u64 next_expiry; + struct timerqueue_head events; + u8 childmask; + unsigned int level; + struct list_head list; + int numa_node; + unsigned int num_children; +}; + +/** + * struct tmigr_cpu - timer migration per CPU group + * @lock: Lock protecting the tmigr_cpu group information + * @online: Indicates whether the CPU is online; In deactivate path + * it is required to know whether the migrator in the top + * level group is on the way to go offline when a timer is + * pending. Then another online CPU needs to be rescheduled + * to make sure the timers are handled properly; + * Furthermore the information is required in CPU hotplug + * path as the CPU is able to go idle before the timer + * migration hierarchy hotplug AP is reached. During this + * phase, the CPU has to handle the global timers by its + * own and does not act as a migrator. + * @idle: Indicates whether the CPU is idle in the timer migration + * hierarchy + * @remote: Is set when timers of the CPU are expired remote + * @wakeup_recalc: Indicates, whether a recalculation of the @wakeup value + * is required. It is only used when the CPU is marked idle + * in the timer migration hierarchy. + * @tmgroup: Pointer to the parent group + * @childmask: childmask of tmigr_cpu in the parent group + * @wakeup: Stores the first timer when the timer migration + * hierarchy is completely idle and remote expiry was done; + * is returned to timer code in the idle path; it is only + * valid, when @wakeup_recalc is not set + * @cpuevt: CPU event which could be queued into the parent group + */ +struct tmigr_cpu { + raw_spinlock_t lock; + bool online; + bool idle; + bool remote; + bool wakeup_recalc; + struct tmigr_group *tmgroup; + u8 childmask; + u64 wakeup; + struct tmigr_event cpuevt; +}; + +/** + * union tmigr_state - state of tmigr_group + * @state: Combined version of the state - only used for atomic + * read/cmpxchg function + * @struct: Split version of the state - only use the struct members to + * update information to stay independent of endianness + */ +union tmigr_state { + u32 state; + /** + * struct - split state of tmigr_group + * @active: Contains each childmask bit of the active children + * @migrator: Contains childmask of the child which is migrator + * @seq: Sequence counter needs to be increased when an update + * to the tmigr_state is done. It prevents a race when + * updates in the child groups are propagated in changed + * order. Detailed information about the scenario is + * given in the documentation at the begin of + * timer_migration.c. + */ + struct { + u8 active; + u8 migrator; + u16 seq; + } __packed; +}; + +#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON) +extern void tmigr_handle_remote(void); +extern int tmigr_requires_handle_remote(void); +extern void tmigr_cpu_activate(void); +extern u64 tmigr_cpu_deactivate(u64 nextevt); +extern u64 tmigr_cpu_new_timer(u64 nextevt); +extern u64 tmigr_quick_check(void); +#else +static inline void tmigr_handle_remote(void) { } +static inline int tmigr_requires_handle_remote(void) { return 0; } +static inline void tmigr_cpu_activate(void) { } +#endif + +#endif --=20 2.39.2 From nobody Mon Dec 29 03:02:50 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A0ACFC4167B for ; Fri, 1 Dec 2023 09:29:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378160AbjLAJ3J (ORCPT ); Fri, 1 Dec 2023 04:29:09 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52392 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378148AbjLAJ2R (ORCPT ); Fri, 1 Dec 2023 04:28:17 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3FFB11FD9 for ; Fri, 1 Dec 2023 01:27:30 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422848; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ZXDeEjIBNXYe4LZ65KgmZyDO9TwDwGVuKUpoOVmxOWc=; b=zm31mmUk2IjTpxPYsC6/ialV0ay+XIkmitMWTaydrVJdz6B3TKLisJeKPPGvg5dErxwEHD v9zjHLfgWJxRLchQkayhTIjIgJQm/FPDfari+Kp5ipgw/Bd3gJWDxQGWHh0YDoMQPEKwDg Yp3Z7YUzWpgAluAUJSReQlykqtm+8koH1B1inrAlm4GuOAYcbezZm+j5BquS5UQF+f5JRG hNbP91HjSVbq2cS6E00VIvm/lnapYOuMjyAhFAsICEd3oJJcPGzk9BTnCxkSUh6BpHdcYp DDHbfH/zwH04KxwfIf5j5Wzz+Pm7l1nEHNcC1NJwDRMGund+pT0fueJ1hrOsIA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422848; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ZXDeEjIBNXYe4LZ65KgmZyDO9TwDwGVuKUpoOVmxOWc=; b=p9mSNC+mdFKvEq4pxhCmglgSSShce5hxYxXZE6i/056/w2VrmsQ8Me+Ms3lu+DRytfJ61c 7JzJMkCgoePaajBw== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen Subject: [PATCH v9 31/32] timer_migration: Add tracepoints Date: Fri, 1 Dec 2023 10:26:53 +0100 Message-Id: <20231201092654.34614-32-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" The timer pull logic needs proper debugging aids. Add tracepoints so the hierarchical idle machinery can be diagnosed. Signed-off-by: Anna-Maria Behnsen --- v9: Add tmigr_cpu_new_timer_idle tracepoint v8: Add wakeup value to tracepoints --- include/trace/events/timer_migration.h | 297 +++++++++++++++++++++++++ kernel/time/timer_migration.c | 26 +++ 2 files changed, 323 insertions(+) create mode 100644 include/trace/events/timer_migration.h diff --git a/include/trace/events/timer_migration.h b/include/trace/events/= timer_migration.h new file mode 100644 index 000000000000..a2e7e32058f8 --- /dev/null +++ b/include/trace/events/timer_migration.h @@ -0,0 +1,297 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ + +#undef TRACE_SYSTEM +#define TRACE_SYSTEM timer_migration + +#if !defined(_TRACE_TIMER_MIGRATION_H) || defined(TRACE_HEADER_MULTI_READ) +#define _TRACE_TIMER_MIGRATION_H + +#include + +/* Group events */ +TRACE_EVENT(tmigr_group_set, + + TP_PROTO(struct tmigr_group *group), + + TP_ARGS(group), + + TP_STRUCT__entry( + __field( void *, group ) + __field( unsigned int, lvl ) + __field( unsigned int, numa_node ) + ), + + TP_fast_assign( + __entry->group =3D group; + __entry->lvl =3D group->level; + __entry->numa_node =3D group->numa_node; + ), + + TP_printk("group=3D%p lvl=3D%d numa=3D%d", + __entry->group, __entry->lvl, __entry->numa_node) +); + +TRACE_EVENT(tmigr_connect_child_parent, + + TP_PROTO(struct tmigr_group *child), + + TP_ARGS(child), + + TP_STRUCT__entry( + __field( void *, child ) + __field( void *, parent ) + __field( unsigned int, lvl ) + __field( unsigned int, numa_node ) + __field( unsigned int, num_children ) + __field( u32, childmask ) + ), + + TP_fast_assign( + __entry->child =3D child; + __entry->parent =3D child->parent; + __entry->lvl =3D child->parent->level; + __entry->numa_node =3D child->parent->numa_node; + __entry->numa_node =3D child->parent->num_children; + __entry->childmask =3D child->childmask; + ), + + TP_printk("group=3D%p childmask=3D%0x parent=3D%p lvl=3D%d numa=3D%d num_= children=3D%d", + __entry->child, __entry->childmask, __entry->parent, + __entry->lvl, __entry->numa_node, __entry->num_children) +); + +TRACE_EVENT(tmigr_connect_cpu_parent, + + TP_PROTO(struct tmigr_cpu *tmc), + + TP_ARGS(tmc), + + TP_STRUCT__entry( + __field( void *, parent ) + __field( unsigned int, cpu ) + __field( unsigned int, lvl ) + __field( unsigned int, numa_node ) + __field( unsigned int, num_children ) + __field( u32, childmask ) + ), + + TP_fast_assign( + __entry->parent =3D tmc->tmgroup; + __entry->cpu =3D tmc->cpuevt.cpu; + __entry->lvl =3D tmc->tmgroup->level; + __entry->numa_node =3D tmc->tmgroup->numa_node; + __entry->numa_node =3D tmc->tmgroup->num_children; + __entry->childmask =3D tmc->childmask; + ), + + TP_printk("cpu=3D%d childmask=3D%0x parent=3D%p lvl=3D%d numa=3D%d num_ch= ildren=3D%d", + __entry->cpu, __entry->childmask, __entry->parent, + __entry->lvl, __entry->numa_node, __entry->num_children) +); + +DECLARE_EVENT_CLASS(tmigr_group_and_cpu, + + TP_PROTO(struct tmigr_group *group, union tmigr_state state, u32 childmas= k), + + TP_ARGS(group, state, childmask), + + TP_STRUCT__entry( + __field( void *, group ) + __field( void *, parent ) + __field( unsigned int, lvl ) + __field( unsigned int, numa_node ) + __field( u8, active ) + __field( u8, migrator ) + __field( u32, childmask ) + ), + + TP_fast_assign( + __entry->group =3D group; + __entry->parent =3D group->parent; + __entry->lvl =3D group->level; + __entry->numa_node =3D group->numa_node; + __entry->active =3D state.active; + __entry->migrator =3D state.migrator; + __entry->childmask =3D childmask; + ), + + TP_printk("group=3D%p lvl=3D%d numa=3D%d active=3D%0x migrator=3D%0x " + "parent=3D%p childmask=3D%0x", + __entry->group, __entry->lvl, __entry->numa_node, + __entry->active, __entry->migrator, + __entry->parent, __entry->childmask) +); + +DEFINE_EVENT(tmigr_group_and_cpu, tmigr_group_set_cpu_inactive, + + TP_PROTO(struct tmigr_group *group, union tmigr_state state, u32 childmas= k), + + TP_ARGS(group, state, childmask) +); + +DEFINE_EVENT(tmigr_group_and_cpu, tmigr_group_set_cpu_active, + + TP_PROTO(struct tmigr_group *group, union tmigr_state state, u32 childmas= k), + + TP_ARGS(group, state, childmask) +); + +/* CPU events*/ +DECLARE_EVENT_CLASS(tmigr_cpugroup, + + TP_PROTO(struct tmigr_cpu *tmc), + + TP_ARGS(tmc), + + TP_STRUCT__entry( + __field( void *, parent) + __field( unsigned int, cpu) + __field( u64, wakeup) + ), + + TP_fast_assign( + __entry->cpu =3D tmc->cpuevt.cpu; + __entry->parent =3D tmc->tmgroup; + __entry->wakeup =3D tmc->wakeup; + ), + + TP_printk("cpu=3D%d parent=3D%p wakeup=3D%llu", __entry->cpu, __entry->pa= rent, __entry->wakeup) +); + +DEFINE_EVENT(tmigr_cpugroup, tmigr_cpu_new_timer, + + TP_PROTO(struct tmigr_cpu *tmc), + + TP_ARGS(tmc) +); + +DEFINE_EVENT(tmigr_cpugroup, tmigr_cpu_active, + + TP_PROTO(struct tmigr_cpu *tmc), + + TP_ARGS(tmc) +); + +DEFINE_EVENT(tmigr_cpugroup, tmigr_cpu_online, + + TP_PROTO(struct tmigr_cpu *tmc), + + TP_ARGS(tmc) +); + +DEFINE_EVENT(tmigr_cpugroup, tmigr_cpu_offline, + + TP_PROTO(struct tmigr_cpu *tmc), + + TP_ARGS(tmc) +); + +DEFINE_EVENT(tmigr_cpugroup, tmigr_handle_remote_cpu, + + TP_PROTO(struct tmigr_cpu *tmc), + + TP_ARGS(tmc) +); + +DECLARE_EVENT_CLASS(tmigr_idle, + + TP_PROTO(struct tmigr_cpu *tmc, u64 nextevt), + + TP_ARGS(tmc, nextevt), + + TP_STRUCT__entry( + __field( void *, parent) + __field( unsigned int, cpu) + __field( u64, nextevt) + __field( u64, wakeup) + ), + + TP_fast_assign( + __entry->cpu =3D tmc->cpuevt.cpu; + __entry->parent =3D tmc->tmgroup; + __entry->nextevt =3D nextevt; + __entry->wakeup =3D tmc->wakeup; + ), + + TP_printk("cpu=3D%d parent=3D%p nextevt=3D%llu wakeup=3D%llu", + __entry->cpu, __entry->parent, __entry->nextevt, __entry->wakeup) +); + +DEFINE_EVENT(tmigr_idle, tmigr_cpu_idle, + + TP_PROTO(struct tmigr_cpu *tmc, u64 nextevt), + + TP_ARGS(tmc, nextevt) +); + +DEFINE_EVENT(tmigr_idle, tmigr_cpu_new_timer_idle, + + TP_PROTO(struct tmigr_cpu *tmc, u64 nextevt), + + TP_ARGS(tmc, nextevt) +); + +TRACE_EVENT(tmigr_update_events, + + TP_PROTO(struct tmigr_group *child, struct tmigr_group *group, + union tmigr_state childstate, union tmigr_state groupstate, + u64 nextevt), + + TP_ARGS(child, group, childstate, groupstate, nextevt), + + TP_STRUCT__entry( + __field( void *, child ) + __field( void *, group ) + __field( u64, nextevt ) + __field( u64, group_next_expiry ) + __field( unsigned int, group_lvl ) + __field( u8, child_active ) + __field( u8, group_active ) + __field( unsigned int, child_evtcpu ) + __field( u64, child_evt_expiry ) + ), + + TP_fast_assign( + __entry->child =3D child; + __entry->group =3D group; + __entry->nextevt =3D nextevt; + __entry->group_next_expiry =3D group->next_expiry; + __entry->group_lvl =3D group->level; + __entry->child_active =3D childstate.active; + __entry->group_active =3D groupstate.active; + __entry->child_evtcpu =3D child ? child->groupevt.cpu : 0; + __entry->child_evt_expiry =3D child ? child->groupevt.nextevt.expires : = 0; + ), + + TP_printk("child=3D%p group=3D%p group_lvl=3D%d child_active=3D%0x group_= active=3D%0x " + "nextevt=3D%llu next_expiry=3D%llu child_evt_expiry=3D%llu child_evtcp= u=3D%d", + __entry->child, __entry->group, __entry->group_lvl, __entry->child_act= ive, + __entry->group_active, + __entry->nextevt, __entry->group_next_expiry, __entry->child_evt_expir= y, + __entry->child_evtcpu) +); + +TRACE_EVENT(tmigr_handle_remote, + + TP_PROTO(struct tmigr_group *group), + + TP_ARGS(group), + + TP_STRUCT__entry( + __field( void * , group ) + __field( unsigned int , lvl ) + ), + + TP_fast_assign( + __entry->group =3D group; + __entry->lvl =3D group->level; + ), + + TP_printk("group=3D%p lvl=3D%d", + __entry->group, __entry->lvl) +); + +#endif /* _TRACE_TIMER_MIGRATION_H */ + +/* This part must be outside protection */ +#include diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c index 05cd8f1bc45d..54ab18ccc62b 100644 --- a/kernel/time/timer_migration.c +++ b/kernel/time/timer_migration.c @@ -14,6 +14,9 @@ #include "timer_migration.h" #include "tick-internal.h" =20 +#define CREATE_TRACE_POINTS +#include + /* * The timer migration mechanism is built on a hierarchy of groups. The * lowest level group contains CPUs, the next level groups of CPU groups @@ -511,6 +514,8 @@ static bool tmigr_active_up(struct tmigr_group *group, */ group->groupevt.ignore =3D true; =20 + trace_tmigr_group_set_cpu_active(group, newstate, childmask); + return walk_done; } =20 @@ -521,6 +526,8 @@ static void __tmigr_cpu_activate(struct tmigr_cpu *tmc) data.childmask =3D tmc->childmask; data.groupstate.state =3D atomic_read(&tmc->tmgroup->migr_state); =20 + trace_tmigr_cpu_active(tmc); + tmc->cpuevt.ignore =3D true; WRITE_ONCE(tmc->wakeup, KTIME_MAX); tmc->wakeup_recalc =3D false; @@ -688,6 +695,9 @@ static bool tmigr_update_events(struct tmigr_group *gro= up, data->nextexp =3D tmigr_next_groupevt_expires(group); } =20 + trace_tmigr_update_events(child, group, data->childstate, + data->groupstate, nextexp); + unlock: raw_spin_unlock(&group->lock); =20 @@ -721,6 +731,8 @@ static u64 tmigr_new_timer(struct tmigr_cpu *tmc, u64 n= extexp) if (tmc->remote) return KTIME_MAX; =20 + trace_tmigr_cpu_new_timer(tmc); + tmc->cpuevt.ignore =3D false; data.remote =3D false; =20 @@ -754,6 +766,8 @@ static u64 tmigr_handle_remote_cpu(unsigned int cpu, u6= 4 now, return next; } =20 + trace_tmigr_handle_remote_cpu(tmc); + tmc->remote =3D true; WRITE_ONCE(tmc->wakeup, KTIME_MAX); =20 @@ -838,6 +852,7 @@ static bool tmigr_handle_remote_up(struct tmigr_group *= group, =20 childmask =3D data->childmask; =20 + trace_tmigr_handle_remote(group); again: /* * Handle the group only if @childmask is the migrator or if the @@ -1101,6 +1116,7 @@ u64 tmigr_cpu_new_timer(u64 nextexp) */ WRITE_ONCE(tmc->wakeup, ret); =20 + trace_tmigr_cpu_new_timer_idle(tmc, nextexp); raw_spin_unlock(&tmc->lock); return ret; } @@ -1210,6 +1226,8 @@ static bool tmigr_inactive_up(struct tmigr_group *gro= up, } } =20 + trace_tmigr_group_set_cpu_inactive(group, newstate, childmask); + return walk_done; } =20 @@ -1264,6 +1282,7 @@ u64 tmigr_cpu_deactivate(u64 nextexp) */ WRITE_ONCE(tmc->wakeup, ret); =20 + trace_tmigr_cpu_idle(tmc, nextexp); raw_spin_unlock(&tmc->lock); return ret; } @@ -1376,6 +1395,7 @@ static struct tmigr_group *tmigr_get_group(unsigned i= nt cpu, int node, =20 /* Setup successful. Add it to the hierarchy */ list_add(&group->list, &tmigr_level_list[lvl]); + trace_tmigr_group_set(group); return group; } =20 @@ -1393,6 +1413,8 @@ static void tmigr_connect_child_parent(struct tmigr_g= roup *child, raw_spin_unlock(&parent->lock); raw_spin_unlock_irq(&child->lock); =20 + trace_tmigr_connect_child_parent(child); + /* * To prevent inconsistent states, active children need to be active in * the new parent as well. Inactive children are already marked inactive @@ -1474,6 +1496,8 @@ static int tmigr_setup_groups(unsigned int cpu, unsig= ned int node) =20 raw_spin_unlock_irq(&group->lock); =20 + trace_tmigr_connect_cpu_parent(tmc); + /* There are no children that need to be connected */ continue; } else { @@ -1541,6 +1565,7 @@ static int tmigr_cpu_online(unsigned int cpu) WRITE_ONCE(tmc->wakeup, KTIME_MAX); } raw_spin_lock_irq(&tmc->lock); + trace_tmigr_cpu_online(tmc); if (timer_base_is_idle()) tmc->idle =3D true; else @@ -1563,6 +1588,7 @@ static int tmigr_cpu_offline(unsigned int cpu) * offline; Therefore nextevt value is set to KTIME_MAX */ __tmigr_cpu_deactivate(tmc, KTIME_MAX); + trace_tmigr_cpu_offline(tmc); raw_spin_unlock_irq(&tmc->lock); =20 return 0; --=20 2.39.2 From nobody Mon Dec 29 03:02:50 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 605E9C4167B for ; Fri, 1 Dec 2023 09:29:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378200AbjLAJ3H (ORCPT ); Fri, 1 Dec 2023 04:29:07 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52370 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378201AbjLAJ2R (ORCPT ); Fri, 1 Dec 2023 04:28:17 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0D88E1FDD for ; Fri, 1 Dec 2023 01:27:30 -0800 (PST) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701422849; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=QYexXRgS2m5/dffYZ2zGFXnxjxh6wHD+OeXAnIrdHS4=; b=CaKDJWrMIQ2XDsHebkDLVj6vhfpY1bVbxlutZsI2FXCWK5GlSqOp9ycw/krKlnZcFKGsaX jSZcx3uZRM97ThMaXYFFFJmCWI864VKBNRpf92bkHuN3DykbJ7cDnWITVhwupQzdBiMR3C VDhuTVto3q6v34p/0MU4EEmoa+i01EcMnxju8dE+Lb9C7Qubv7nrrElqNIBRevESh3OjqH Ky8ewq1ml+IcXQspz+Wrw1MZ0tUyQ2JHWZuX5fn8Vc/JxL9l60YggYqiXRQsnsAftvNM5f g9gDlKPSCoZlnABDbZ1fGARLiMBLefQ5l8uNx3F8nCiWoJIR+yEnQIH+TaC+cQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701422849; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=QYexXRgS2m5/dffYZ2zGFXnxjxh6wHD+OeXAnIrdHS4=; b=A0lpCutDv4FDkeQp+mxGZD/cO52q4pGv2KnxDGTXksG1RQRM0/MTNKD+h5e0wys3W7C0zA IZU3vnjknhOnYjAA== To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , Eric Dumazet , "Rafael J . Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Steven Rostedt , Sebastian Siewior , Giovanni Gherdovich , Lukasz Luba , "Gautham R . Shenoy" , Srinivas Pandruvada , K Prateek Nayak , Anna-Maria Behnsen , Richard Cochran Subject: [PATCH v9 32/32] timers: Always queue timers on the local CPU Date: Fri, 1 Dec 2023 10:26:54 +0100 Message-Id: <20231201092654.34614-33-anna-maria@linutronix.de> In-Reply-To: <20231201092654.34614-1-anna-maria@linutronix.de> References: <20231201092654.34614-1-anna-maria@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" The timer pull model is in place so we can remove the heuristics which try to guess the best target CPU at enqueue/modification time. All non pinned timers are queued on the local CPU in the separate storage and eventually pulled at expiry time to a remote CPU. Originally-by: Richard Cochran (linutronix GmbH) Signed-off-by: Anna-Maria Behnsen --- v9: - Update to the changes of the preceding patches v6: - Update TIMER_PINNED flag description. v5: - Move WARN_ONCE() in add_timer_on() into a previous patch - Fold crystallball magic related hunks into this patch v4: Update comment about TIMER_PINNED flag (heristic is removed) --- include/linux/timer.h | 14 ++++--------- kernel/time/timer.c | 46 +++++++++++++++++++++---------------------- 2 files changed, 26 insertions(+), 34 deletions(-) diff --git a/include/linux/timer.h b/include/linux/timer.h index 404bb31a95c7..4dd59e4e5681 100644 --- a/include/linux/timer.h +++ b/include/linux/timer.h @@ -50,16 +50,10 @@ struct timer_list { * workqueue locking issues. It's not meant for executing random crap * with interrupts disabled. Abuse is monitored! * - * @TIMER_PINNED: A pinned timer will not be affected by any timer - * placement heuristics (like, NOHZ) and will always expire on the CPU - * on which the timer was enqueued. - * - * Note: Because enqueuing of timers can migrate the timer from one - * CPU to another, pinned timers are not guaranteed to stay on the - * initialy selected CPU. They move to the CPU on which the enqueue - * function is invoked via mod_timer() or add_timer(). If the timer - * should be placed on a particular CPU, then add_timer_on() has to be - * used. + * @TIMER_PINNED: A pinned timer will always expire on the CPU on which the + * timer was enqueued. When a particular CPU is required, add_timer_on() + * has to be used. Enqueue via mod_timer() and add_timer() is always done + * on the local CPU. */ #define TIMER_CPUMASK 0x0003FFFF #define TIMER_MIGRATING 0x00040000 diff --git a/kernel/time/timer.c b/kernel/time/timer.c index ac3e888d053f..6e9e1d852438 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -590,10 +590,13 @@ trigger_dyntick_cpu(struct timer_base *base, struct t= imer_list *timer) =20 /* * We might have to IPI the remote CPU if the base is idle and the - * timer is not deferrable. If the other CPU is on the way to idle - * then it can't set base->is_idle as we hold the base lock: + * timer is pinned. If it is a non pinned timer, it is only queued + * on the remote CPU, when timer was running during queueing. Then + * everything is handled by remote CPU anyway. If the other CPU is + * on the way to idle then it can't set base->is_idle as we hold + * the base lock: */ - if (base->is_idle) + if (base->is_idle && timer->flags & TIMER_PINNED) wake_up_nohz_cpu(base->cpu); } =20 @@ -941,17 +944,6 @@ static inline struct timer_base *get_timer_base(u32 tf= lags) return get_timer_cpu_base(tflags, tflags & TIMER_CPUMASK); } =20 -static inline struct timer_base * -get_target_base(struct timer_base *base, unsigned tflags) -{ -#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON) - if (static_branch_likely(&timers_migration_enabled) && - !(tflags & TIMER_PINNED)) - return get_timer_cpu_base(tflags, get_nohz_timer_target()); -#endif - return get_timer_this_cpu_base(tflags); -} - static inline void __forward_timer_base(struct timer_base *base, unsigned long basej) { @@ -1106,7 +1098,7 @@ __mod_timer(struct timer_list *timer, unsigned long e= xpires, unsigned int option if (!ret && (options & MOD_TIMER_PENDING_ONLY)) goto out_unlock; =20 - new_base =3D get_target_base(base, timer->flags); + new_base =3D get_timer_this_cpu_base(timer->flags); =20 if (base !=3D new_base) { /* @@ -2228,11 +2220,17 @@ static inline u64 __get_next_timer_interrupt(unsign= ed long basej, u64 basem, * BASE_GLOBAL base, deferrable timers may still see large * granularity skew (by design). */ - if (!base_local->is_idle) { - bool is_idle =3D time_after(nextevt, basej + 1); =20 - base_local->is_idle =3D base_global->is_idle =3D is_idle; - } + /* + * base->is_idle information is required to wakeup an idle CPU + * when a new timer was enqueued. Only pinned timers could be + * enqueued remotely into a idle base. Therefore do maintain + * only base_local->is_idle information and ignore + * base_global->is_idle information. + */ + if (!base_local->is_idle) + base_local->is_idle =3D time_after(nextevt, basej + 1); + *idle =3D base_local->is_idle; trace_timer_base_idle(base_local->is_idle, base_local->cpu); =20 @@ -2307,13 +2305,13 @@ bool timer_base_is_idle(void) void timer_clear_idle(void) { /* - * We do this unlocked. The worst outcome is a remote enqueue sending - * a pointless IPI, but taking the lock would just make the window for - * sending the IPI a few instructions smaller for the cost of taking - * the lock in the exit from idle path. + * We do this unlocked. The worst outcome is a remote pinned timer + * enqueue sending a pointless IPI, but taking the lock would just + * make the window for sending the IPI a few instructions smaller + * for the cost of taking the lock in the exit from idle + * path. Required for BASE_LOCAL only. */ __this_cpu_write(timer_bases[BASE_LOCAL].is_idle, false); - __this_cpu_write(timer_bases[BASE_GLOBAL].is_idle, false); =20 trace_timer_base_idle(0, smp_processor_id()); =20 --=20 2.39.2