From nobody Wed Sep 10 02:01:35 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 B629DE7B604 for ; Wed, 4 Oct 2023 12:36:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242537AbjJDMgS (ORCPT ); Wed, 4 Oct 2023 08:36:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39370 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242421AbjJDMfp (ORCPT ); Wed, 4 Oct 2023 08:35:45 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 55F1E109 for ; Wed, 4 Oct 2023 05:35:38 -0700 (PDT) From: Anna-Maria Behnsen DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1696422936; 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=QACr81bz714MeCGL3gllUl2Nlnw9ik8CMB4MxkBQEQc=; b=K8cDLMkhIl9jSNDDBcAcfHcoA/acgRfw443uKotsXCB7uc3qnguuRXlXa5Kqc3BmdkjVuO nnCkb02YomwFh5lpEv33jfrAX4zsDb/UlGY2OdPS7TVV2KcQDNIVArnsfnwQcJshzjdrgf z5KjhSlTMj29E69cROikykyYCAVPz915PKq/J4A6PqHEO6+5+gy6Z6fRq6vTmUn1DpFDf3 yzHYsGwhdu1eCoMorK0lLGPECTRnvluV8lk71vKtW6/Y0KjltbFQjiOHAnARTHwarKxHgC /vo6NqgtHhgx8aAjCO/T3Sey5zJxVvejS389q64glxIudCkMboAC7cYZ0/5Jkw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1696422936; 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=QACr81bz714MeCGL3gllUl2Nlnw9ik8CMB4MxkBQEQc=; b=RXiLI0RQZzrhT3E/isMxxk+c+AZeO2+fDmy/adcP9ISHbDsdDhqoMABYMgPukXHa7ndD2W DgstDnFJ8iuZL0CQ== 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 v8 19/25] timer: Add get next timer interrupt functionality for remote CPUs Date: Wed, 4 Oct 2023 14:34:48 +0200 Message-Id: <20231004123454.15691-20-anna-maria@linutronix.de> In-Reply-To: <20231004123454.15691-1-anna-maria@linutronix.de> References: <20231004123454.15691-1-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 b035606a6f5e..206010ae2a53 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 c3061b28214e..ae4b6f62b082 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); @@ -2016,6 +2011,77 @@ static unsigned long fetch_next_timer_interrupt(unsi= gned long basej, u64 basem, return local_first ? nextevt_local : nextevt_global; } =20 +# ifdef CONFIG_SMP +/** + * fetch_next_timer_interrupt_remote + * @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 unsigned long __get_next_timer_interrupt(unsigned long basej= , u64 basem, struct timer_base *base_local, struct timer_base *base_global, --=20 2.39.2