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 CB1571DD0C7 for ; Mon, 17 Mar 2025 16:47:35 +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=1742230057; cv=none; b=PkiBKbl3/3EsI8rW+qUfghmEut13gVbZ/jkeqEMPX6jm0+yfVaUUf1z/um4y52LICIc+7/gkZwJYMSiOkO+rKFwWEqI6xkWew5EEtxqyK60sSTopDQj5wuMMyTw0ml/IysLs3Yfwqj4WQQzsVfuSLYXvHaSa39k/8KMJSVG/vNo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742230057; c=relaxed/simple; bh=fqAWorI/IijoDnsIyNR5wVArlprAf6Lh35mcV9x3xtQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=cBwVG0YHWeW97642PfVCOxRhufgb1X/LnJXYdSvfgw4n3FI4NViK9oZlsz7UgDRKXfFXnf159lUe9JQBzkIdIacOvPnEPYy2UTA1VXUAOYLtBGVS3rigLH3/tu+4uWfzaxT823JajOazB4oL7xhVeO3SvgLqP6HqUPn7kdk7Rxc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (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=PjnrT51g; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (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="PjnrT51g" 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=oyC7+eWfCsY2ldWxknayBsCHD5+HuepYtp8UG/Q2UVA=; b=PjnrT51gHGSXw/2l7Ehb+pocoO MmfOl/48ouEk/T07tbDgSb3r9sjuUmkiLmwAbNtWIZnv8ATKvNtpGfzwleT9SHRAW46+OLwhJhx+m GICefSWOkWMnQMUclo3w6limTEhxlJrtxE6teJVqd+x63NlqssHKknfu6w0c3mutY+3d4fpvtmhWq yRM5JruRxeC26Por+JrXwN4oHRx6a/h54FuEoGV0mZN+QP2adxZvjtkaiMKbBhNEVZwp5okWeVggJ 9iqPWC5F1W9PNdTi2Z3jDQ0jZrmSdS/lzYB0TQQ3V7o9Q7kOrIXwo+xEwGP10XbhI41f7+0vEoG1d VbY+ezfg==; 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 (Red Hat Linux)) id 1tuDcc-00000003Uk3-0Go7; Mon, 17 Mar 2025 16:47:26 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 843D7300783; Mon, 17 Mar 2025 17:47:25 +0100 (CET) Date: Mon, 17 Mar 2025 17:47:25 +0100 From: Peter Zijlstra To: John Stultz Cc: LKML , Joel Fernandes , Qais Yousef , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Ben Segall , Zimuzo Ezeozue , Mel Gorman , Will Deacon , Waiman Long , Boqun Feng , "Paul E. McKenney" , Metin Kaya , Xuewen Yan , K Prateek Nayak , Thomas Gleixner , Daniel Lezcano , Suleiman Souhlal , kernel-team@android.com, Valentin Schneider , Connor O'Brien Subject: Re: [RFC PATCH v15 7/7] sched: Start blocked_on chain processing in find_proxy_task() Message-ID: <20250317164725.GC6888@noisy.programming.kicks-ass.net> References: <20250312221147.1865364-1-jstultz@google.com> <20250312221147.1865364-8-jstultz@google.com> 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: <20250312221147.1865364-8-jstultz@google.com> On Wed, Mar 12, 2025 at 03:11:37PM -0700, John Stultz wrote: > @@ -6791,6 +6890,7 @@ static void __sched notrace __schedule(int sched_mode) > struct rq_flags rf; > struct rq *rq; > int cpu; > + bool preserve_need_resched = false; > > cpu = smp_processor_id(); > rq = cpu_rq(cpu); > @@ -6858,9 +6958,12 @@ static void __sched notrace __schedule(int sched_mode) > next = find_proxy_task(rq, next, &rf); > if (!next) > goto pick_again; > + if (next == rq->idle) > + preserve_need_resched = true; > } > picked: > - clear_tsk_need_resched(prev); > + if (!preserve_need_resched) > + clear_tsk_need_resched(prev); > clear_preempt_need_resched(); > #ifdef CONFIG_SCHED_DEBUG > rq->last_seen_need_resched_ns = 0; I would really rather this was done like so: --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -6957,12 +6944,12 @@ static void __sched notrace __schedule(i if (!next) goto pick_again; if (next == rq->idle) - preserve_need_resched = true; + goto keep_resched; } picked: - if (!preserve_need_resched) - clear_tsk_need_resched(prev); + clear_tsk_need_resched(prev); clear_preempt_need_resched(); +keep_resched: #ifdef CONFIG_SCHED_DEBUG rq->last_seen_need_resched_ns = 0; #endif