From nobody Fri May 8 03:49:56 2026 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 7B0D0C433F5 for ; Wed, 11 May 2022 19:48:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347288AbiEKTsF (ORCPT ); Wed, 11 May 2022 15:48:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33642 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347230AbiEKTr2 (ORCPT ); Wed, 11 May 2022 15:47:28 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A6DF648E7F; Wed, 11 May 2022 12:47:16 -0700 (PDT) Date: Wed, 11 May 2022 19:47:14 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1652298435; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=YmQvPuEemCy6jk8V3JajePFDy8INIYM6/UxwXz6/XdE=; b=wVrz0WrbWNOkg5yPxHfsp69FiY7q2eJUVfFrtO+bT16LeSUqhukzlERsvAtyf+6S106DUr YIFIqc4bK9hCkVPArbp9azojZcMxHCjUN7mtMqRDAAKOruaRaY/2se590AwBg3CKCjpZ3o yA5ryEM+fGfCocnZ4UoqCnbUElez32CFzhbVVNqZdhqC/jlBnZsxKDiSOmenktoI16iosh o9IDHFyO4qNc77uQdQoD+HjPpDllzXaL40G7Ve85xZwC2IreuYPssaqoIqhaRbF5qdBq55 EmqufNucbHGM2YUU1cj+pdQng2noJMIbsgFH6iv+u3Eq4syJh+XsAlDQEbJutg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1652298435; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=YmQvPuEemCy6jk8V3JajePFDy8INIYM6/UxwXz6/XdE=; b=nOqPzsT9W4SBJ1zKQ9hlnauyfwzM+A5qwEzNoSSNBDyKAnIEjclpqyRSvnS72WnasR8lvZ dseXz25YlG0EKJCg== From: "tip-bot2 for Hao Jia" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] sched/core: Avoid obvious double update_rq_clock warning Cc: Hao Jia , "Peter Zijlstra (Intel)" , Dietmar Eggemann , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20220430085843.62939-2-jiahao.os@bytedance.com> References: <20220430085843.62939-2-jiahao.os@bytedance.com> MIME-Version: 1.0 Message-ID: <165229843417.4207.14886909568720858111.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/core branch of tip: Commit-ID: 2679a83731d51a744657f718fc02c3b077e47562 Gitweb: https://git.kernel.org/tip/2679a83731d51a744657f718fc02c3b07= 7e47562 Author: Hao Jia AuthorDate: Sat, 30 Apr 2022 16:58:42 +08:00 Committer: Peter Zijlstra CommitterDate: Wed, 11 May 2022 16:27:11 +02:00 sched/core: Avoid obvious double update_rq_clock warning When we use raw_spin_rq_lock() to acquire the rq lock and have to update the rq clock while holding the lock, the kernel may issue a WARN_DOUBLE_CLOCK warning. Since we directly use raw_spin_rq_lock() to acquire rq lock instead of rq_lock(), there is no corresponding change to rq->clock_update_flags. In particular, we have obtained the rq lock of other CPUs, the rq->clock_update_flags of this CPU may be RQCF_UPDATED at this time, and then calling update_rq_clock() will trigger the WARN_DOUBLE_CLOCK warning. So we need to clear RQCF_UPDATED of rq->clock_update_flags to avoid the WARN_DOUBLE_CLOCK warning. For the sched_rt_period_timer() and migrate_task_rq_dl() cases we simply replace raw_spin_rq_lock()/raw_spin_rq_unlock() with rq_lock()/rq_unlock(). For the {pull,push}_{rt,dl}_task() cases, we add the double_rq_clock_clear_update() function to clear RQCF_UPDATED of rq->clock_update_flags, and call double_rq_clock_clear_update() before double_lock_balance()/double_rq_lock() returns to avoid the WARN_DOUBLE_CLOCK warning. Some call trace reports: Call Trace 1: sched_rt_period_timer+0x10f/0x3a0 ? enqueue_top_rt_rq+0x110/0x110 __hrtimer_run_queues+0x1a9/0x490 hrtimer_interrupt+0x10b/0x240 __sysvec_apic_timer_interrupt+0x8a/0x250 sysvec_apic_timer_interrupt+0x9a/0xd0 asm_sysvec_apic_timer_interrupt+0x12/0x20 Call Trace 2: activate_task+0x8b/0x110 push_rt_task.part.108+0x241/0x2c0 push_rt_tasks+0x15/0x30 finish_task_switch+0xaa/0x2e0 ? __switch_to+0x134/0x420 __schedule+0x343/0x8e0 ? hrtimer_start_range_ns+0x101/0x340 schedule+0x4e/0xb0 do_nanosleep+0x8e/0x160 hrtimer_nanosleep+0x89/0x120 ? hrtimer_init_sleeper+0x90/0x90 __x64_sys_nanosleep+0x96/0xd0 do_syscall_64+0x34/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae Call Trace 3: deactivate_task+0x93/0xe0 pull_rt_task+0x33e/0x400 balance_rt+0x7e/0x90 __schedule+0x62f/0x8e0 do_task_dead+0x3f/0x50 do_exit+0x7b8/0xbb0 do_group_exit+0x2d/0x90 get_signal+0x9df/0x9e0 ? preempt_count_add+0x56/0xa0 ? __remove_hrtimer+0x35/0x70 arch_do_signal_or_restart+0x36/0x720 ? nanosleep_copyout+0x39/0x50 ? do_nanosleep+0x131/0x160 ? audit_filter_inodes+0xf5/0x120 exit_to_user_mode_prepare+0x10f/0x1e0 syscall_exit_to_user_mode+0x17/0x30 do_syscall_64+0x40/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae Call Trace 4: update_rq_clock+0x128/0x1a0 migrate_task_rq_dl+0xec/0x310 set_task_cpu+0x84/0x1e4 try_to_wake_up+0x1d8/0x5c0 wake_up_process+0x1c/0x30 hrtimer_wakeup+0x24/0x3c __hrtimer_run_queues+0x114/0x270 hrtimer_interrupt+0xe8/0x244 arch_timer_handler_phys+0x30/0x50 handle_percpu_devid_irq+0x88/0x140 generic_handle_domain_irq+0x40/0x60 gic_handle_irq+0x48/0xe0 call_on_irq_stack+0x2c/0x60 do_interrupt_handler+0x80/0x84 Steps to reproduce: 1. Enable CONFIG_SCHED_DEBUG when compiling the kernel 2. echo 1 > /sys/kernel/debug/clear_warn_once echo "WARN_DOUBLE_CLOCK" > /sys/kernel/debug/sched/features echo "NO_RT_PUSH_IPI" > /sys/kernel/debug/sched/features 3. Run some rt/dl tasks that periodically work and sleep, e.g. Create 2*n rt or dl (90% running) tasks via rt-app (on a system with n CPUs), and Dietmar Eggemann reports Call Trace 4 when running on PREEMPT_RT kernel. Signed-off-by: Hao Jia Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Dietmar Eggemann Link: https://lore.kernel.org/r/20220430085843.62939-2-jiahao.os@bytedance.= com --- kernel/sched/core.c | 6 +++--- kernel/sched/deadline.c | 5 +++-- kernel/sched/rt.c | 5 +++-- kernel/sched/sched.h | 28 ++++++++++++++++++++++++---- 4 files changed, 33 insertions(+), 11 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 48cfad1..2c9f5e9 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -613,10 +613,10 @@ void double_rq_lock(struct rq *rq1, struct rq *rq2) swap(rq1, rq2); =20 raw_spin_rq_lock(rq1); - if (__rq_lockp(rq1) =3D=3D __rq_lockp(rq2)) - return; + if (__rq_lockp(rq1) !=3D __rq_lockp(rq2)) + raw_spin_rq_lock_nested(rq2, SINGLE_DEPTH_NESTING); =20 - raw_spin_rq_lock_nested(rq2, SINGLE_DEPTH_NESTING); + double_rq_clock_clear_update(rq1, rq2); } #endif =20 diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 6ae4236..0ad2818 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1830,6 +1830,7 @@ out: =20 static void migrate_task_rq_dl(struct task_struct *p, int new_cpu __maybe_= unused) { + struct rq_flags rf; struct rq *rq; =20 if (READ_ONCE(p->__state) !=3D TASK_WAKING) @@ -1841,7 +1842,7 @@ static void migrate_task_rq_dl(struct task_struct *p,= int new_cpu __maybe_unused * from try_to_wake_up(). Hence, p->pi_lock is locked, but * rq->lock is not... So, lock it */ - raw_spin_rq_lock(rq); + rq_lock(rq, &rf); if (p->dl.dl_non_contending) { update_rq_clock(rq); sub_running_bw(&p->dl, &rq->dl); @@ -1857,7 +1858,7 @@ static void migrate_task_rq_dl(struct task_struct *p,= int new_cpu __maybe_unused put_task_struct(p); } sub_rq_bw(&p->dl, &rq->dl); - raw_spin_rq_unlock(rq); + rq_unlock(rq, &rf); } =20 static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p) diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index a32c468..7891c0f 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -871,6 +871,7 @@ static int do_sched_rt_period_timer(struct rt_bandwidth= *rt_b, int overrun) int enqueue =3D 0; struct rt_rq *rt_rq =3D sched_rt_period_rt_rq(rt_b, i); struct rq *rq =3D rq_of_rt_rq(rt_rq); + struct rq_flags rf; int skip; =20 /* @@ -885,7 +886,7 @@ static int do_sched_rt_period_timer(struct rt_bandwidth= *rt_b, int overrun) if (skip) continue; =20 - raw_spin_rq_lock(rq); + rq_lock(rq, &rf); update_rq_clock(rq); =20 if (rt_rq->rt_time) { @@ -923,7 +924,7 @@ static int do_sched_rt_period_timer(struct rt_bandwidth= *rt_b, int overrun) =20 if (enqueue) sched_rt_rq_enqueue(rt_rq); - raw_spin_rq_unlock(rq); + rq_unlock(rq, &rf); } =20 if (!throttled && (!rt_bandwidth_enabled() || rt_b->rt_runtime =3D=3D RUN= TIME_INF)) diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 7f338c5..fe4d1ac 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -2474,6 +2474,24 @@ unsigned long arch_scale_freq_capacity(int cpu) } #endif =20 +#ifdef CONFIG_SCHED_DEBUG +/* + * In double_lock_balance()/double_rq_lock(), we use raw_spin_rq_lock() to + * acquire rq lock instead of rq_lock(). So at the end of these two functi= ons + * we need to call double_rq_clock_clear_update() to clear RQCF_UPDATED of + * rq->clock_update_flags to avoid the WARN_DOUBLE_CLOCK warning. + */ +static inline void double_rq_clock_clear_update(struct rq *rq1, struct rq = *rq2) +{ + rq1->clock_update_flags &=3D (RQCF_REQ_SKIP|RQCF_ACT_SKIP); + /* rq1 =3D=3D rq2 for !CONFIG_SMP, so just clear RQCF_UPDATED once. */ +#ifdef CONFIG_SMP + rq2->clock_update_flags &=3D (RQCF_REQ_SKIP|RQCF_ACT_SKIP); +#endif +} +#else +static inline void double_rq_clock_clear_update(struct rq *rq1, struct rq = *rq2) {} +#endif =20 #ifdef CONFIG_SMP =20 @@ -2539,14 +2557,15 @@ static inline int _double_lock_balance(struct rq *t= his_rq, struct rq *busiest) __acquires(busiest->lock) __acquires(this_rq->lock) { - if (__rq_lockp(this_rq) =3D=3D __rq_lockp(busiest)) - return 0; - - if (likely(raw_spin_rq_trylock(busiest))) + if (__rq_lockp(this_rq) =3D=3D __rq_lockp(busiest) || + likely(raw_spin_rq_trylock(busiest))) { + double_rq_clock_clear_update(this_rq, busiest); return 0; + } =20 if (rq_order_less(this_rq, busiest)) { raw_spin_rq_lock_nested(busiest, SINGLE_DEPTH_NESTING); + double_rq_clock_clear_update(this_rq, busiest); return 0; } =20 @@ -2640,6 +2659,7 @@ static inline void double_rq_lock(struct rq *rq1, str= uct rq *rq2) BUG_ON(rq1 !=3D rq2); raw_spin_rq_lock(rq1); __acquire(rq2->lock); /* Fake it out ;) */ + double_rq_clock_clear_update(rq1, rq2); } =20 /*