From nobody Sun Feb 8 22:35:22 2026 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7A9FD31A046; Thu, 16 Oct 2025 09:33:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760607230; cv=none; b=CjLsHt2ZDJQOhbYUq2fnkue4weT705GUvLUVCUpnGEvEMwS279RpwyqUKGp1jCzXIy0mRFK7HVwKImlZUR8qXeGlgEogdOpZaI9udHBgM3WBlEgB+ZNX0Ma6rWNF1/W6Afhv5N7aPPdj/RjzxaGPvhvkSt2kzp5PqkFJuBQh3FY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760607230; c=relaxed/simple; bh=RRasjwLFBUj83MX96nymx91YlkNRKmzQTP+iv56OJX8=; h=Date:From:To:Subject:Cc:In-Reply-To:References:MIME-Version: Message-ID:Content-Type; b=Z2RHvT0ZCL9ATEZ7TArBgyx1AKM55Zj63zwE0gYggSj/P2Wfo14jTIetO59Vzq4YU/f6EqXO9kpxbNegDp/ErRoXeKX111odB4QCJuPFx3SMPW5Yv5TmRHHZCiyTfpFkzaXInDUyP2lSjQM45vsOM61IREF36CrecKYXGc5c95M= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=m/GypFc2; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=SAhHxqBt; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="m/GypFc2"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="SAhHxqBt" Date: Thu, 16 Oct 2025 09:33:45 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1760607227; 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=E8R0luGVEbWQ5MerGOXY9BLBqVO99/2Nrg3PPLHwJd8=; b=m/GypFc2lFDyPz8aH3zH0NnaCcQmCQSa9UY39IEj3TnACR0mnaA38VySQ7zLipI0YAuP2j bZ7UFg7Dvjb0kxAMh0srPlHB/91g++MSz7WNuuyyv74VAzzw23xpqm0kVGkxjtM5610g9P KLJZwTAeaKIe+vo/1hNOzlGPravFrktEoiV+vvFGMnOzyEf5SuyK0yOAEzcoBXgdo7FgDF CmFjAnR6aKrzdLDioe/hGCMcb3WtB8w2EOaCvk0FtR+yg6uwbNlZ8VU3oHE1gq/5Qwlt1I CkUdJwAouKwajAySWHbeR5+RmotSVF0bVg4KC49hzv1yECoyWrFbd61e+HiqiQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1760607227; 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=E8R0luGVEbWQ5MerGOXY9BLBqVO99/2Nrg3PPLHwJd8=; b=SAhHxqBtycT4uvDN9dFBBkoFh5zEhJZwCT+sONEp/eJWKbUlx6XEp6Xoh5lS30yB1AFzLb OXptbPnl/IZ5dwBA== From: "tip-bot2 for Doug Berger" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] sched/deadline: only set free_cpus for online runqueues Cc: Doug Berger , "Peter Zijlstra (Intel)" , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20250815012236.4053467-1-opendmb@gmail.com> References: <20250815012236.4053467-1-opendmb@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <176060722582.709179.1540483623189425427.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Precedence: bulk Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable The following commit has been merged into the sched/core branch of tip: Commit-ID: 382748c05e58a9f1935f5a653c352422375566ea Gitweb: https://git.kernel.org/tip/382748c05e58a9f1935f5a653c3524223= 75566ea Author: Doug Berger AuthorDate: Thu, 14 Aug 2025 18:22:36 -07:00 Committer: Peter Zijlstra CommitterDate: Thu, 16 Oct 2025 11:13:49 +02:00 sched/deadline: only set free_cpus for online runqueues Commit 16b269436b72 ("sched/deadline: Modify cpudl::free_cpus to reflect rd->online") introduced the cpudl_set/clear_freecpu functions to allow the cpu_dl::free_cpus mask to be manipulated by the deadline scheduler class rq_on/offline callbacks so the mask would also reflect this state. Commit 9659e1eeee28 ("sched/deadline: Remove cpu_active_mask from cpudl_find()") removed the check of the cpu_active_mask to save some processing on the premise that the cpudl::free_cpus mask already reflected the runqueue online state. Unfortunately, there are cases where it is possible for the cpudl_clear function to set the free_cpus bit for a CPU when the deadline runqueue is offline. When this occurs while a CPU is connected to the default root domain the flag may retain the bad state after the CPU has been unplugged. Later, a different CPU that is transitioning through the default root domain may push a deadline task to the powered down CPU when cpudl_find sees its free_cpus bit is set. If this happens the task will not have the opportunity to run. One example is outlined here: https://lore.kernel.org/lkml/20250110233010.2339521-1-opendmb@gmail.com Another occurs when the last deadline task is migrated from a CPU that has an offlined runqueue. The dequeue_task member of the deadline scheduler class will eventually call cpudl_clear and set the free_cpus bit for the CPU. This commit modifies the cpudl_clear function to be aware of the online state of the deadline runqueue so that the free_cpus mask can be updated appropriately. It is no longer necessary to manage the mask outside of the cpudl_set/clear functions so the cpudl_set/clear_freecpu functions are removed. In addition, since the free_cpus mask is now only updated under the cpudl lock the code was changed to use the non-atomic __cpumask functions. Signed-off-by: Doug Berger Signed-off-by: Peter Zijlstra (Intel) --- kernel/sched/cpudeadline.c | 34 +++++++++------------------------- kernel/sched/cpudeadline.h | 4 +--- kernel/sched/deadline.c | 8 ++++---- 3 files changed, 14 insertions(+), 32 deletions(-) diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c index cdd740b..37b572c 100644 --- a/kernel/sched/cpudeadline.c +++ b/kernel/sched/cpudeadline.c @@ -166,12 +166,13 @@ int cpudl_find(struct cpudl *cp, struct task_struct *= p, * cpudl_clear - remove a CPU from the cpudl max-heap * @cp: the cpudl max-heap context * @cpu: the target CPU + * @online: the online state of the deadline runqueue * * Notes: assumes cpu_rq(cpu)->lock is locked * * Returns: (void) */ -void cpudl_clear(struct cpudl *cp, int cpu) +void cpudl_clear(struct cpudl *cp, int cpu, bool online) { int old_idx, new_cpu; unsigned long flags; @@ -184,7 +185,7 @@ void cpudl_clear(struct cpudl *cp, int cpu) if (old_idx =3D=3D IDX_INVALID) { /* * Nothing to remove if old_idx was invalid. - * This could happen if a rq_offline_dl is + * This could happen if rq_online_dl or rq_offline_dl is * called for a CPU without -dl tasks running. */ } else { @@ -195,9 +196,12 @@ void cpudl_clear(struct cpudl *cp, int cpu) cp->elements[new_cpu].idx =3D old_idx; cp->elements[cpu].idx =3D IDX_INVALID; cpudl_heapify(cp, old_idx); - - cpumask_set_cpu(cpu, cp->free_cpus); } + if (likely(online)) + __cpumask_set_cpu(cpu, cp->free_cpus); + else + __cpumask_clear_cpu(cpu, cp->free_cpus); + raw_spin_unlock_irqrestore(&cp->lock, flags); } =20 @@ -228,7 +232,7 @@ void cpudl_set(struct cpudl *cp, int cpu, u64 dl) cp->elements[new_idx].cpu =3D cpu; cp->elements[cpu].idx =3D new_idx; cpudl_heapify_up(cp, new_idx); - cpumask_clear_cpu(cpu, cp->free_cpus); + __cpumask_clear_cpu(cpu, cp->free_cpus); } else { cp->elements[old_idx].dl =3D dl; cpudl_heapify(cp, old_idx); @@ -238,26 +242,6 @@ void cpudl_set(struct cpudl *cp, int cpu, u64 dl) } =20 /* - * cpudl_set_freecpu - Set the cpudl.free_cpus - * @cp: the cpudl max-heap context - * @cpu: rd attached CPU - */ -void cpudl_set_freecpu(struct cpudl *cp, int cpu) -{ - cpumask_set_cpu(cpu, cp->free_cpus); -} - -/* - * cpudl_clear_freecpu - Clear the cpudl.free_cpus - * @cp: the cpudl max-heap context - * @cpu: rd attached CPU - */ -void cpudl_clear_freecpu(struct cpudl *cp, int cpu) -{ - cpumask_clear_cpu(cpu, cp->free_cpus); -} - -/* * cpudl_init - initialize the cpudl structure * @cp: the cpudl max-heap context */ diff --git a/kernel/sched/cpudeadline.h b/kernel/sched/cpudeadline.h index 11c0f1f..d769946 100644 --- a/kernel/sched/cpudeadline.h +++ b/kernel/sched/cpudeadline.h @@ -19,8 +19,6 @@ struct cpudl { =20 int cpudl_find(struct cpudl *cp, struct task_struct *p, struct cpumask *l= ater_mask); void cpudl_set(struct cpudl *cp, int cpu, u64 dl); -void cpudl_clear(struct cpudl *cp, int cpu); +void cpudl_clear(struct cpudl *cp, int cpu, bool online); int cpudl_init(struct cpudl *cp); -void cpudl_set_freecpu(struct cpudl *cp, int cpu); -void cpudl_clear_freecpu(struct cpudl *cp, int cpu); void cpudl_cleanup(struct cpudl *cp); diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 615411a..933bd1f 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1808,7 +1808,7 @@ static void dec_dl_deadline(struct dl_rq *dl_rq, u64 = deadline) if (!dl_rq->dl_nr_running) { dl_rq->earliest_dl.curr =3D 0; dl_rq->earliest_dl.next =3D 0; - cpudl_clear(&rq->rd->cpudl, rq->cpu); + cpudl_clear(&rq->rd->cpudl, rq->cpu, rq->online); cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio.curr); } else { struct rb_node *leftmost =3D rb_first_cached(&dl_rq->root); @@ -2880,9 +2880,10 @@ static void rq_online_dl(struct rq *rq) if (rq->dl.overloaded) dl_set_overload(rq); =20 - cpudl_set_freecpu(&rq->rd->cpudl, rq->cpu); if (rq->dl.dl_nr_running > 0) cpudl_set(&rq->rd->cpudl, rq->cpu, rq->dl.earliest_dl.curr); + else + cpudl_clear(&rq->rd->cpudl, rq->cpu, true); } =20 /* Assumes rq->lock is held */ @@ -2891,8 +2892,7 @@ static void rq_offline_dl(struct rq *rq) if (rq->dl.overloaded) dl_clear_overload(rq); =20 - cpudl_clear(&rq->rd->cpudl, rq->cpu); - cpudl_clear_freecpu(&rq->rd->cpudl, rq->cpu); + cpudl_clear(&rq->rd->cpudl, rq->cpu, false); } =20 void __init init_sched_dl_class(void)