From nobody Mon Feb 9 05:41:32 2026 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 5349218A6BA for ; Thu, 29 Aug 2024 13:54:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724939675; cv=none; b=RIwBwCvz5TO9blX9A9nidOYQVMQ+0dYp+u3PS50Jd2dOvNdvqRit7Z4JR6XsXBur15EKM5CIZKX5XZcjm6ZNY77FjYDQycPz9VLVS4Qox0zq+vXlBsQ5RdFJ6E1ifJkHRRkQyVI8fubLl0k6o7CuIbyY8trct5+ER0m4VyIFIKI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724939675; c=relaxed/simple; bh=Rq+yNcUwPWx41zQSO5KmqMvIsQRScXdlmsTqVPKSxf0=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=P42fZkaW8luqw2lZZFHk4bSJrEVJQ1vesOMVXv98xP9Pn8mfZdTh9OCzSBKNBXB0/GWFHjlcok3eOaIlaDa6aDI8b4+lORyHXz8/W6qtfkrQkNhQ7jJxkoFy14cqMoOtzKeEeMpwZaps+Mg6DqGHzRjgD03CEvjq7bxHxXdgkWg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=SubGUyCe; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="SubGUyCe" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1724939672; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=vX4yi4Z2CPW0eHhvuU5h0SjR1OL4/r7rT7T4GvJLHuA=; b=SubGUyCeSOS7qbafiRU4i9Ov4/tOK9fWsjL72SXWTN+1cLH+jdjs6O6MTbP78O7bDjaA9w tmfanBzfBICNkdAtm4vyxRVJYii8QDCygiGKpRn6fGzY+roSPnPUOIJKAG2htUA16//Anr prPzwLB23+f9O2rHb+mvyEcqAjMhHGI= Received: from mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-203-y2zAJ-lJPRiKUMMPommj5Q-1; Thu, 29 Aug 2024 09:54:29 -0400 X-MC-Unique: y2zAJ-lJPRiKUMMPommj5Q-1 Received: from mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.15]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 531E51955BF1; Thu, 29 Aug 2024 13:54:26 +0000 (UTC) Received: from vschneid-thinkpadt14sgen2i.remote.csb (unknown [10.39.194.25]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 16B9519560AA; Thu, 29 Aug 2024 13:54:20 +0000 (UTC) From: Valentin Schneider To: linux-kernel@vger.kernel.org Cc: "Paul E. McKenney" , Chen Yu , mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, kprateek.nayak@amd.com, wuyun.abel@bytedance.com, youssefesmat@chromium.org, tglx@linutronix.de, efault@gmx.de Subject: [PATCH] sched/fair: Properly deactivate sched_delayed task upon class change Date: Thu, 29 Aug 2024 15:53:53 +0200 Message-ID: <20240829135353.1524260-1-vschneid@redhat.com> 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-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 Content-Type: text/plain; charset="utf-8" __sched_setscheduler() goes through an enqueue/dequeue cycle like so: flags :=3D DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK; prev_class->dequeue_task(rq, p, flags); new_class->enqueue_task(rq, p, flags); when prev_class :=3D fair_sched_class, this is followed by: dequeue_task(rq, p, DEQUEUE_NOCLOCK | DEQUEUE_SLEEP); the idea being that since the task has switched classes, we need to drop the sched_delayed logic and have that task be deactivated per its previous dequeue_task(..., DEQUEUE_SLEEP). Unfortunately, this leaves the task on_rq. This is missing the tail end of dequeue_entities() that issues __block_task(), which __sched_setscheduler() won't have done due to not using DEQUEUE_DELAYED - not that it should, as it is pretty much a fair_sched_class specific thing. Make switched_from_fair() properly deactivate sched_delayed tasks upon class changes via __block_task(), as if a dequeue_task(..., DEQUEUE_DELAYED) had been issued. Fixes: 2e0199df252a ("sched/fair: Prepare exit/cleanup paths for delayed_de= queue") Reported-by: "Paul E. McKenney" Reported-by: Chen Yu Signed-off-by: Valentin Schneider --- kernel/sched/fair.c | 25 +++++++++++++++++-------- 1 file changed, 17 insertions(+), 8 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index fea057b311f69..3a3286df282fc 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5456,6 +5456,13 @@ static void clear_buddies(struct cfs_rq *cfs_rq, str= uct sched_entity *se) =20 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq); =20 +static inline void finish_delayed_dequeue_entity(struct sched_entity *se) +{ + se->sched_delayed =3D 0; + if (sched_feat(DELAY_ZERO) && se->vlag > 0) + se->vlag =3D 0; +} + static bool dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) { @@ -5531,11 +5538,8 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_e= ntity *se, int flags) if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) !=3D DEQUEUE_SAVE) update_min_vruntime(cfs_rq); =20 - if (flags & DEQUEUE_DELAYED) { - se->sched_delayed =3D 0; - if (sched_feat(DELAY_ZERO) && se->vlag > 0) - se->vlag =3D 0; - } + if (flags & DEQUEUE_DELAYED) + finish_delayed_dequeue_entity(se); =20 if (cfs_rq->nr_running =3D=3D 0) update_idle_cfs_rq_clock_pelt(cfs_rq); @@ -13107,11 +13111,16 @@ static void switched_from_fair(struct rq *rq, str= uct task_struct *p) * and we cannot use DEQUEUE_DELAYED. */ if (p->se.sched_delayed) { + /* First, dequeue it from its new class' structures */ dequeue_task(rq, p, DEQUEUE_NOCLOCK | DEQUEUE_SLEEP); - p->se.sched_delayed =3D 0; + /* + * Now, clean up the fair_sched_class side of things + * related to sched_delayed being true and that wasn't done + * due to the generic dequeue not using DEQUEUE_DELAYED. + */ + finish_delayed_dequeue_entity(&p->se); p->se.rel_deadline =3D 0; - if (sched_feat(DELAY_ZERO) && p->se.vlag > 0) - p->se.vlag =3D 0; + __block_task(rq, p); } } =20 --=20 2.43.0