From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 504EBC433EF for ; Tue, 8 Mar 2022 18:53:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236634AbiCHSyE (ORCPT ); Tue, 8 Mar 2022 13:54:04 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53208 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1349823AbiCHSwo (ORCPT ); Tue, 8 Mar 2022 13:52:44 -0500 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 512B457B34; Tue, 8 Mar 2022 10:51:41 -0800 (PST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A4CB41516; Tue, 8 Mar 2022 10:51:41 -0800 (PST) Received: from wubuntu (unknown [10.57.71.199]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 65FF13FA45; Tue, 8 Mar 2022 10:51:40 -0800 (PST) Date: Tue, 8 Mar 2022 18:51:38 +0000 From: Qais Yousef To: Greg KH Cc: linux-kernel@vger.kernel.org, linux-tip-commits@vger.kernel.org, Abhijeet Dharmapurikar , Valentin Schneider , "Peter Zijlstra (Intel)" , "Steven Rostedt (Google)" , x86@kernel.org, stable@vger.kernel.org Subject: Re: [tip: sched/core] sched/tracing: Don't re-read p->state when emitting sched_switch event Message-ID: <20220308185138.ldxfqd242uxowymd@wubuntu> References: <20220120162520.570782-2-valentin.schneider@arm.com> <164614827941.16921.4995078681021904041.tip-bot2@tip-bot2> <20220308180240.qivyjdn4e3te3urm@wubuntu> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/08/22 19:10, Greg KH wrote: > On Tue, Mar 08, 2022 at 06:02:40PM +0000, Qais Yousef wrote: > > +CC stable > > > > On 03/01/22 15:24, tip-bot2 for Valentin Schneider wrote: > > > The following commit has been merged into the sched/core branch of tip: > > > > > > Commit-ID: fa2c3254d7cfff5f7a916ab928a562d1165f17bb > > > Gitweb: https://git.kernel.org/tip/fa2c3254d7cfff5f7a916ab928a562d1165f17bb > > > Author: Valentin Schneider > > > AuthorDate: Thu, 20 Jan 2022 16:25:19 > > > Committer: Peter Zijlstra > > > CommitterDate: Tue, 01 Mar 2022 16:18:39 +01:00 > > > > > > sched/tracing: Don't re-read p->state when emitting sched_switch event > > > > > > As of commit > > > > > > c6e7bd7afaeb ("sched/core: Optimize ttwu() spinning on p->on_cpu") > > > > > > the following sequence becomes possible: > > > > > > p->__state = TASK_INTERRUPTIBLE; > > > __schedule() > > > deactivate_task(p); > > > ttwu() > > > READ !p->on_rq > > > p->__state=TASK_WAKING > > > trace_sched_switch() > > > __trace_sched_switch_state() > > > task_state_index() > > > return 0; > > > > > > TASK_WAKING isn't in TASK_REPORT, so the task appears as TASK_RUNNING in > > > the trace event. > > > > > > Prevent this by pushing the value read from __schedule() down the trace > > > event. > > > > > > Reported-by: Abhijeet Dharmapurikar > > > Signed-off-by: Valentin Schneider > > > Signed-off-by: Peter Zijlstra (Intel) > > > Reviewed-by: Steven Rostedt (Google) > > > Link: https://lore.kernel.org/r/20220120162520.570782-2-valentin.schneider@arm.com > > > > Any objection to picking this for stable? I'm interested in this one for some > > Android users but prefer if it can be taken by stable rather than backport it > > individually. > > > > I think it makes sense to pick the next one in the series too. > > What commit does this fix in Linus's tree? It should be this one: c6e7bd7afaeb ("sched/core: Optimize ttwu() spinning on p->on_cpu") Not sure about the 2nd patch, but I can try to figure it out. > Once it hits Linus's tree, let stable@vger.kernel.org know what the git > commit id is in Linus's tree. Sure. My bad if I rushed the request. I just wanted to know whether it's okay for this to go into stable. If no one shouts, I'll ping once it lands in Linus'. Thanks! -- Qais Yousef