From nobody Sun Feb 8 04:57:34 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 822C821ADCB; Fri, 23 Jan 2026 11:06:39 +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=1769166400; cv=none; b=nszupDCs2+nsI1M/oaGT1bi7O9rMtR4qEgged4DsQ74icSkgyd5kKYBdPfuOUQl8jgu6R2DTbGVssaeSBn88XD0bzJeAnRKXMqA9eM+oFlVfxWeO5g+64Pizwr6tdB4JfBSJDQgwct05q3sNEf4O5HjSFjYJB+tWM946o00FOOI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769166400; c=relaxed/simple; bh=xSnRmKz3jDLIXBUeu+AYjBcmkHTmMvA0AsjGNMH/W28=; h=Date:From:To:Subject:Cc:In-Reply-To:References:MIME-Version: Message-ID:Content-Type; b=iNB7Iu6SE0RATVqvB0VWnb9r6u/zc6SjQSN6109YwKGG2qV/szPco/QEsRU98oT+PCwtYINTZBb1PyPQB8bhUkTCzyr2NMFNeQBZvbYoPgBZJdeNUhIKZOybSvbc28SPDkEirC0Le6O094zzW8FnVoBGLdw1IvSuKJCJ3W3A5nM= 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=hIibv/RA; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=ltdt/v9F; 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="hIibv/RA"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="ltdt/v9F" Date: Fri, 23 Jan 2026 11:06:31 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1769166398; 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=4Z3d4jZchfCm28WHk6qz3M8/+MhQ48NC+ky0PUGJgzo=; b=hIibv/RAsS1QHHxiDFpklFRAOuBVr/S1X2UaJRtETFk1FDggGjJN3SMCu4aF+rLzhXsilQ pSP5LRGIYg2svha5LyYSGNuEH/sm3oCJOa1vV9PuXWYAyuEI5WdT2D1b7RAumzgqnnoEbC B1qG91/lHabXF+ZdtppKegHEcI04h5cJXyS+mrIHsIaZLy3wvGY8ztF47LbwMmy25dAFZc gzzC+g9mNJsYS/qXCb05acxXDX3OmN8tLUiccE/1KQahEeEyEJbEqDJO96fG9GynGDsXe5 CZK9UO1UPg3dV8aN/s70tCDYWa9Yp6+YxXfPyKfpH2f/YMQ8GSOR5p7rJJg1rw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1769166398; 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=4Z3d4jZchfCm28WHk6qz3M8/+MhQ48NC+ky0PUGJgzo=; b=ltdt/v9FydbsbI1Fu7cCN4dGNI9bVevX1d2Ez0jGV5bkmy6MR9UpPJpUZq50tIMjHbmjzE PRDKfgCvC+2/ZMDg== From: "tip-bot2 for Vincent Guittot" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/urgent] sched/fair: Revert force wakeup preemption Cc: Vincent Guittot , "Peter Zijlstra (Intel)" , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20260123102858.52428-1-vincent.guittot@linaro.org> References: <20260123102858.52428-1-vincent.guittot@linaro.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <176916639187.510.1647095982279283388.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/urgent branch of tip: Commit-ID: 15257cc2f905dbf5813c0bfdd3c15885f28093c4 Gitweb: https://git.kernel.org/tip/15257cc2f905dbf5813c0bfdd3c15885f= 28093c4 Author: Vincent Guittot AuthorDate: Fri, 23 Jan 2026 11:28:58 +01:00 Committer: Peter Zijlstra CommitterDate: Fri, 23 Jan 2026 11:53:20 +01:00 sched/fair: Revert force wakeup preemption This agressively bypasses run_to_parity and slice protection with the assumpiton that this is what waker wants but there is no garantee that the wakee will be the next to run. It is a better choice to use yield_to_task or WF_SYNC in such case. This increases the number of resched and preemption because a task becomes quickly "ineligible" when it runs; We update the task vruntime periodically and before the task exhausted its slice or at least quantum. Example: 2 tasks A and B wake up simultaneously with lag =3D 0. Both are eligible. Task A runs 1st and wakes up task C. Scheduler updates task A's vruntime which becomes greater than average runtime as all others have a lag =3D=3D 0 and didn't run yet. Now task A is ineligible because it received more runtime than the other task but it has not yet exhausted its slice nor a min quantum. We force preemption, disable protection but Task B will run 1st not task C. Sidenote, DELAY_ZERO increases this effect by clearing positive lag at wake up. Fixes: e837456fdca8 ("sched/fair: Reimplement NEXT_BUDDY to align with EEVD= F goals") Signed-off-by: Vincent Guittot Signed-off-by: Peter Zijlstra (Intel) Link: https://patch.msgid.link/20260123102858.52428-1-vincent.guittot@linar= o.org --- kernel/sched/fair.c | 10 ---------- 1 file changed, 10 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index a148c61..3eaeced 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -8828,16 +8828,6 @@ static void check_preempt_wakeup_fair(struct rq *rq,= struct task_struct *p, int=20 if ((wake_flags & WF_FORK) || pse->sched_delayed) return; =20 - /* - * If @p potentially is completing work required by current then - * consider preemption. - * - * Reschedule if waker is no longer eligible. */ - if (in_task() && !entity_eligible(cfs_rq, se)) { - preempt_action =3D PREEMPT_WAKEUP_RESCHED; - goto preempt; - } - /* Prefer picking wakee soon if appropriate. */ if (sched_feat(NEXT_BUDDY) && set_preempt_buddy(cfs_rq, wake_flags, pse, se)) {