From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 3C34C2BDC32 for ; Fri, 1 May 2026 14:49:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777646995; cv=none; b=Z6Oh638ECPCMP1sciiieo+7Ko7jfsAmBPPYu4sxty83579HYP0azBu6OmQ0nT4elFapR0i5o5YkGxh05A2VJHLCSUEDXCRUrtSds2DlJk4zKRXouHPF0MzmVeXfejh++fORuH1jpeZwAc//FtzqZlIS7m0bRo0fq50BdJGqMmVc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777646995; c=relaxed/simple; bh=3DVCKOorda0JfvLpWS5s8lxGY62ME9qWmfa1A+wr+Jg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=LFfTHJ78/NY0ezwPL/ktYPU60Kq4a1or/dAIieUMzm4n6uova8sFj5BDVnlQ0JQWbQWJr/OKVIqgJpCDNdbO7oT4kV2dqjHrua2Pht5xt4X/Vjpqb19mvMAyeeK5UMRb/INkBPp+pp2vbYSA3K28KbNbKuIGpQ/5p2FvE5OwIBQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=f7Mzcuy1; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="f7Mzcuy1" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=3DVCKOorda0JfvLpWS5s8lxGY62ME9qWmfa1A+wr+Jg=; b=f7Mzcuy1FcG/Isk5AwwlUQgrYx xtwyYzY8NuKmuxlN5fQ+PJlUcV71Jzd7QMRMTSxHaMLCaw4WhTApLIuofI5YyLUu7s3ExmIaEVERe qVypjPFW1bLMlpwZi51TwJ8393D6HJZNb4CxQf3b9uPvBgVwMjtl7Z9EUtCRKqEVTrvAfQ4Pwx/Ey /kDjrVlZP7RFE2XnCakLdkDJ27Qy5ShHrX5xUJHXmJC9qrBe/wYWZVFAOgWb1DrG//VbS2O2AZOVZ Axd1Y9Iny7s5MlFzu7xJxE3O/LaDafYm/gdnOA8zn1Y2aNWZllDLrklFXaOH1tmG4oHKUb6h9vwG+ OT3CAo0g==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1wIpBa-000000093ha-44Ah; Fri, 01 May 2026 14:49:47 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 8AD533006CD; Fri, 01 May 2026 16:49:45 +0200 (CEST) Date: Fri, 1 May 2026 16:49:45 +0200 From: Peter Zijlstra To: Vincent Guittot Cc: mingo@redhat.com, juri.lelli@redhat.com, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, kprateek.nayak@amd.com, linux-kernel@vger.kernel.org, qyousef@layalina.io Subject: Re: [PATCH] sched/fair: Fix wakeup_preempt_fair for not waking up task Message-ID: <20260501144945.GE1026330@noisy.programming.kicks-ass.net> References: <20260429164102.1388139-1-vincent.guittot@linaro.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260429164102.1388139-1-vincent.guittot@linaro.org> On Wed, Apr 29, 2026 at 06:41:02PM +0200, Vincent Guittot wrote: > The assumption that p is always enqueued and not delayed, is only true for > wakeup. If p was moved while sched_delayed, pick_next_entity will dequeue > it during the attach and the cfs might become empty. Changelog needs more text on why this is a problem.