From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 4C4D4336EDA; Fri, 9 Jan 2026 12:34:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767962052; cv=none; b=X/TaQCOgKBsQfNHA+LIBsjYb9/xlmt/AIlJDk0zrO6XxJpGdnfF+US6EWIm5lO6Hur9skaefXtJyiJwGvNtMKYc6sC41hMQ0ZKK3UcGrf+nqCmi1QtP4PiPMSGPR3QrEgwc1rPcoJkWlDRDkVshrx+SR3WLz+D96YK3FCIGY0II= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767962052; c=relaxed/simple; bh=352MMNjMXGoaLIsEKbDf36SgAfMQJyaiF3l60LiIBq8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=oFuWPNQJxT4AZmAdLIRXvFOBGKF1Utgk2HaeBDjOKOhxmIS5OczVJIBVgX5b4lyGNSZhvZwKGvttqgA0M0AX+miUsbuQ5+C9dnqGcUeDisqalP1LQgMAlGEzCQgY+yUD+iRzHirp9JNhiBI9cj9/YR2AjQqWJON83POEWzfkK9w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=sYnz7j7R; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="sYnz7j7R" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CCBCAC4CEF1; Fri, 9 Jan 2026 12:34:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1767962052; bh=352MMNjMXGoaLIsEKbDf36SgAfMQJyaiF3l60LiIBq8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=sYnz7j7RwoseBexUB6xcZgv142VFaLbYpwNmD+HaMoNx/tw7zqhHYbqHtD3CbcOlB XwU5UDBhSZLO0hBNFwLLWIgDAAGkAA063OG9wrgDTRAmZ4nmp5MXAxn+y1AIZoDd2I izCDXFSzQMfrBRFhcREg1vZVRCfYhc/c9YMS+T1k= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Doug Berger , "Peter Zijlstra (Intel)" , Sasha Levin Subject: [PATCH 6.1 229/634] sched/deadline: only set free_cpus for online runqueues Date: Fri, 9 Jan 2026 12:38:27 +0100 Message-ID: <20260109112126.046754187@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260109112117.407257400@linuxfoundation.org> References: <20260109112117.407257400@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Doug Berger [ Upstream commit 382748c05e58a9f1935f5a653c352422375566ea ] 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) Signed-off-by: Sasha Levin --- 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 57c92d751bcd7..afa84e1216ee9 100644 --- a/kernel/sched/cpudeadline.c +++ b/kernel/sched/cpudeadline.c @@ -165,12 +165,13 @@ 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; @@ -183,7 +184,7 @@ void cpudl_clear(struct cpudl *cp, int cpu) if (old_idx == 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 { @@ -194,9 +195,12 @@ void cpudl_clear(struct cpudl *cp, int cpu) cp->elements[new_cpu].idx = old_idx; cp->elements[cpu].idx = 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); } @@ -227,7 +231,7 @@ void cpudl_set(struct cpudl *cp, int cpu, u64 dl) cp->elements[new_idx].cpu = cpu; cp->elements[cpu].idx = 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 = dl; cpudl_heapify(cp, old_idx); @@ -236,26 +240,6 @@ void cpudl_set(struct cpudl *cp, int cpu, u64 dl) raw_spin_unlock_irqrestore(&cp->lock, flags); } -/* - * 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 0adeda93b5fb5..ecff718d94aea 100644 --- a/kernel/sched/cpudeadline.h +++ b/kernel/sched/cpudeadline.h @@ -18,9 +18,7 @@ struct cpudl { #ifdef CONFIG_SMP int cpudl_find(struct cpudl *cp, struct task_struct *p, struct cpumask *later_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); #endif /* CONFIG_SMP */ diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 75fe40c6d080f..62a7c4ed86753 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1486,7 +1486,7 @@ static void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline) if (!dl_rq->dl_nr_running) { dl_rq->earliest_dl.curr = 0; dl_rq->earliest_dl.next = 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 = rb_first_cached(&dl_rq->root); @@ -2554,9 +2554,10 @@ static void rq_online_dl(struct rq *rq) if (rq->dl.overloaded) dl_set_overload(rq); - 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); } /* Assumes rq->lock is held */ @@ -2565,8 +2566,7 @@ static void rq_offline_dl(struct rq *rq) if (rq->dl.overloaded) dl_clear_overload(rq); - cpudl_clear(&rq->rd->cpudl, rq->cpu); - cpudl_clear_freecpu(&rq->rd->cpudl, rq->cpu); + cpudl_clear(&rq->rd->cpudl, rq->cpu, false); } void __init init_sched_dl_class(void) -- 2.51.0