linux-kernel - [tip: sched/core] sched/fair: Fixup wake_up_sync() vs DELAYED

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <174782921892.406.11738069373254097989.tip-bot2@tip-bot2>
Date: Wed, 21 May 2025 12:06:58 -0000
From: "tip-bot2 for Xuewen Yan" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Xuewen Yan <xuewen.yan@...soc.com>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>,
 Vincent Guittot <vincent.guittot@...aro.org>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: sched/core] sched/fair: Fixup wake_up_sync() vs DELAYED_DEQUEUE

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     aa3ee4f0b7541382c9f6f43f7408d73a5d4f4042
Gitweb:        https://git.kernel.org/tip/aa3ee4f0b7541382c9f6f43f7408d73a5d4f4042
Author:        Xuewen Yan <xuewen.yan@...soc.com>
AuthorDate:    Mon, 03 Mar 2025 18:52:39 +08:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Wed, 21 May 2025 13:57:37 +02:00

sched/fair: Fixup wake_up_sync() vs DELAYED_DEQUEUE

Delayed dequeued feature keeps a sleeping task enqueued until its
lag has elapsed. As a result, it stays also visible in rq->nr_running.
So when in wake_affine_idle(), we should use the real running-tasks
in rq to check whether we should place the wake-up task to
current cpu.
On the other hand, add a helper function to return the nr-delayed.

Fixes: 152e11f6df29 ("sched/fair: Implement delayed dequeue")
Signed-off-by: Xuewen Yan <xuewen.yan@...soc.com>
Reviewed-and-tested-by: Tianchen Ding <dtcccc@...ux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@...aro.org>
Link: https://lore.kernel.org/r/20250303105241.17251-2-xuewen.yan@unisoc.com
---
 kernel/sched/fair.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index eb5a257..b00f167 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7193,6 +7193,11 @@ static bool dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 	return true;
 }
 
+static inline unsigned int cfs_h_nr_delayed(struct rq *rq)
+{
+	return (rq->cfs.h_nr_queued - rq->cfs.h_nr_runnable);
+}
+
 #ifdef CONFIG_SMP
 
 /* Working cpumask for: sched_balance_rq(), sched_balance_newidle(). */
@@ -7354,8 +7359,12 @@ wake_affine_idle(int this_cpu, int prev_cpu, int sync)
 	if (available_idle_cpu(this_cpu) && cpus_share_cache(this_cpu, prev_cpu))
 		return available_idle_cpu(prev_cpu) ? prev_cpu : this_cpu;
 
-	if (sync && cpu_rq(this_cpu)->nr_running == 1)
-		return this_cpu;
+	if (sync) {
+		struct rq *rq = cpu_rq(this_cpu);
+
+		if ((rq->nr_running - cfs_h_nr_delayed(rq)) == 1)
+			return this_cpu;
+	}
 
 	if (available_idle_cpu(prev_cpu))
 		return prev_cpu;