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 6B1BEC433F5 for ; Mon, 11 Apr 2022 21:06:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1350008AbiDKVIf (ORCPT ); Mon, 11 Apr 2022 17:08:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58910 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230074AbiDKVIa (ORCPT ); Mon, 11 Apr 2022 17:08:30 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id B2D9BB1C3; Mon, 11 Apr 2022 14:06:15 -0700 (PDT) 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 602241570; Mon, 11 Apr 2022 14:06:15 -0700 (PDT) Received: from airbuntu (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2A6473F70D; Mon, 11 Apr 2022 14:06:14 -0700 (PDT) Date: Mon, 11 Apr 2022 22:06:04 +0100 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: <20220411210604.jskouzqxmi7oe7il@airbuntu> References: <20220120162520.570782-2-valentin.schneider@arm.com> <164614827941.16921.4995078681021904041.tip-bot2@tip-bot2> <20220308180240.qivyjdn4e3te3urm@wubuntu> <20220308185138.ldxfqd242uxowymd@wubuntu> <20220409233829.o2s6tffuzujkx6w2@airbuntu> 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 04/11/22 15:22, Greg KH wrote: > On Sun, Apr 10, 2022 at 12:38:29AM +0100, Qais Yousef wrote: > > On 03/08/22 18:51, Qais Yousef wrote: > > > 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") > > > > Should this be okay to be picked up by stable now? I can see AUTOSEL has picked > > it up for v5.15+, but it impacts v5.10 too. > > It does not apply to 5.10 at all, how did you test this? > > {sigh} > > Again, if you want this applied to any stable trees, please test that it > works and send the properly backported patches. Sorry. I'm picking up pieces after a colleague left and was under the impression that 5.10 Android users already use as-is, but due to GKI just need it formally in stable. Few things got lost in translation, I am very sorry! Let me sort all of this out properly including the testing part for 5.15 too. Thanks! -- Qais Yousef