From nobody Thu Sep 24 21:19:45 2026 Received: from m16.mail.163.com (m16.mail.163.com [117.135.210.4]) (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 D8A9135C19B for ; Sun, 20 Sep 2026 04:32:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=117.135.210.4 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789878759; cv=none; b=PqF/EG2/tHkHSPix2byqpFUW8aaTWrfXA5EqEYVPczLD64AWaPT8NTCHWtF9wTJKCVyQNApsNOYMN/iMGbrAIJt2PTF6yj+1Nv7Hv9xELDtvfcW/c10CK5LQdt15xjYsQfe6BcGF8WCznLAOpkm6WFxKhoA4I8DiKIrpULvJbMg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789878759; c=relaxed/simple; bh=71PdsR80XM5px7rYyhqP6gDRRH6XfmmjEXfGrVMG6LI=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=uev+inTBzLIHf+knBIJqA0dVGkY9wumcwUlTNW/PDcqXyhz1Jqcs8YqBlQwcj2+vBezIVydwotOgRz1xAS7vFx5AnNmoPI1DCPc4xOzpJ0ynhTYUUF0naADqFd2nvzZz0rDI1/XPl/H7Lur50THDTnu05/sJANMlU4VWKR7pVIY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com; spf=pass smtp.mailfrom=163.com; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b=m6aLn9Xm; arc=none smtp.client-ip=117.135.210.4 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=163.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b="m6aLn9Xm" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=From:To:Subject:Date:Message-ID:MIME-Version; bh=cX sM1xUTdon1URsuEdOTCMdfWhcDpQJvoeUbDfETOxE=; b=m6aLn9XmsQZXB9wCqn UiZxrmSCZuJm7zk7rUOywzpEIVJPqKfME06zdnMleuXxgrXWWVJbWH+RiCfsYXKl DNewCWesBfqUI2JaKMUJBDnIfGGWsFAn7/90PqSrjq4CnTiLm1/qOps+00jeto5T 7DXFav9kJ7j6UKvYcerLISfCw= Received: from localhost.localdomain (unknown []) by gzga-smtp-mtada-g0-1 (Coremail) with SMTP id _____wD3hmCYYa9qzi_fBg--.59981S2; Sun, 20 Sep 2026 12:31:21 +0800 (CST) From: albin_yang@163.com To: peterz@infradead.org, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org Cc: dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, kprateek.nayak@amd.com, chen.yu@linux.dev, kayracizmeci@gmail.com, mintaohuang@tencent.com, linux-kernel@vger.kernel.org, albin_yang@163.com, albinwyang@tencent.com, Chen Yu Subject: [PATCH v2] sched/stats: Fix run_delay over-count for migrated sched_delayed tasks Date: Sun, 20 Sep 2026 12:31:16 +0800 Message-ID: <20260920043116.1298017-1-albin_yang@163.com> X-Mailer: git-send-email 2.43.7 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: _____wD3hmCYYa9qzi_fBg--.59981S2 X-Coremail-Antispam: 1Uf129KBjvJXoWxXFWkZF1DtrW5GF4xXFy8AFb_yoW5AF4rp3 95Ww1DJa18Kr1rJrnFvr4UWr13uwnrG3y3tFn2yryrKrZ5GF1Yvw42va13XFsYyr9YyFZI va4jg39IyFWqyF7anT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x0ziWE_tUUUUU= X-CM-SenderInfo: pdoex0xb1d0wi6rwjhhfrp/xtbC8BkFp2qvYZnhWAAA3P Content-Type: text/plain; charset="utf-8" From: Wei Yang With DELAY_DEQUEUE, a blocked task stays on the runqueue with se.sched_delayed set and its sched_info.last_queued is cleared, so the sleep is not counted into run_delay. When such a delayed (sleeping) task is migrated across CPUs via the plain migration paths (move_queued_task / move_queued_task_locked, the latter used by __migrate_swap_task), activate_task(dst, 0) calls enqueue_task() without ENQUEUE_RESTORE, re-arming last_queued to the migration timestamp while the task is still sleeping. The later real wakeup (ENQUEUE_DELAYED) tries to re-arm last_queued at wakeup time but is suppressed because last_queued is already non-zero, so sched_info_arrive() folds the whole sleep duration between migration and wakeup into run_delay. Load balance is affected too: the sched_delayed check in can_migrate_task() bails out only when env->migration_type !=3D migrate_load, so it does not block migration when the type is migrate_load - which active load balance always uses (its lb_env leaves migration_type at 0 =3D=3D migrate_load), and which regular load balance can also use via calculate_imbalance(). Either way the re-attach goes through attach_task() -> activate_task(rq, p, ENQUEUE_NOCLOCK), without ENQUEUE_RESTORE. Fix by not re-arming last_queued for a sched_delayed task in sched_info_enqueue(). The wakeup path clears sched_delayed before reaching sched_info_enqueue(), so it still re-arms at the real wakeup time. Plain runnable tasks are unaffected. Fixes: 152e11f6df29 ("sched/fair: Implement delayed dequeue") Reported-by: MingTao Huang Signed-off-by: Wei Yang Reviewed-by: Chen Yu Reviewed-by: K Prateek Nayak Reviewed-by: Kayra Cizmeci Tested-by: K Prateek Nayak --- v1 -> v2: - Correct the claim that load-balance migrations are unaffected: can_migrate_task() only skips a delayed task when migration_type !=3D migrate_load, so active load balance (whose lb_env leaves migration_type at 0 =3D=3D migrate_load) can migrate a sched_delayed ta= sk, as can regular load balance via the migrate_load branches of calculate_imbalance(). The fix covers those paths too; only the description was wrong. Pointed out by Kayra Cizmeci. - Add Chen Yu's Reviewed-by. v1: https://lore.kernel.org/all/20260909133345.1572954-1-albin_yang@163.com/ kernel/sched/stats.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/stats.h b/kernel/sched/stats.h index ebe0a7765f98..dc626f99ffd9 100644 --- a/kernel/sched/stats.h +++ b/kernel/sched/stats.h @@ -290,7 +290,7 @@ static void sched_info_arrive(struct rq *rq, struct tas= k_struct *t) */ static inline void sched_info_enqueue(struct rq *rq, struct task_struct *t) { - if (!t->sched_info.last_queued) + if (!t->sched_info.last_queued && !t->se.sched_delayed) t->sched_info.last_queued =3D rq_clock(rq); } =20 --=20 2.43.7