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 X-Spam-Level: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 50019C47096 for ; Wed, 2 Jun 2021 14:30:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 34A22613BA for ; Wed, 2 Jun 2021 14:30:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230273AbhFBOcR (ORCPT ); Wed, 2 Jun 2021 10:32:17 -0400 Received: from foss.arm.com ([217.140.110.172]:46354 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230031AbhFBOcQ (ORCPT ); Wed, 2 Jun 2021 10:32:16 -0400 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 379C011FB; Wed, 2 Jun 2021 07:30:32 -0700 (PDT) Received: from C02TD0UTHF1T.local (unknown [10.57.31.212]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D16593F73D; Wed, 2 Jun 2021 07:30:19 -0700 (PDT) Date: Wed, 2 Jun 2021 15:30:16 +0100 From: Mark Rutland To: Peter Zijlstra Cc: Mathieu Desnoyers , Thomas Gleixner , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , rostedt , Ben Segall , Mel Gorman , bristot , Borislav Petkov , x86 , "H. Peter Anvin" , Jens Axboe , Alasdair Kergon , Mike Snitzer , dm-devel@redhat.com, "David S. Miller" , Jakub Kicinski , Felipe Balbi , Greg Kroah-Hartman , Alexander Viro , Tejun Heo , Zefan Li , Johannes Weiner , Jason Wessel , Daniel Thompson , Douglas Anderson , acme , Alexander Shishkin , Jiri Olsa , Namhyung Kim , "Rafael J. Wysocki" , Pavel Machek , Will Deacon , Waiman Long , Boqun Feng , Oleg Nesterov , Davidlohr Bueso , paulmck , Josh Triplett , Lai Jiangshan , "Joel Fernandes, Google" , John Stultz , Stephen Boyd , Andrew Morton , Paolo Bonzini , linux-kernel , linux-block@vger.kernel.org, netdev , linux-usb@vger.kernel.org, linux-fsdevel , cgroups , kgdb-bugreport@lists.sourceforge.net, linux-perf-users@vger.kernel.org, linux-pm@vger.kernel.org, rcu , linux-mm , KVM list Subject: Re: [PATCH 3/6] sched,perf,kvm: Fix preemption condition Message-ID: <20210602143016.GE12753@C02TD0UTHF1T.local> References: <20210602131225.336600299@infradead.org> <20210602133040.398289363@infradead.org> <1873020549.5854.1622642347895.JavaMail.zimbra@efficios.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Wed, Jun 02, 2021 at 04:10:29PM +0200, Peter Zijlstra wrote: > On Wed, Jun 02, 2021 at 09:59:07AM -0400, Mathieu Desnoyers wrote: > > ----- On Jun 2, 2021, at 9:12 AM, Peter Zijlstra peterz@infradead.org wrote: > > > > > When ran from the sched-out path (preempt_notifier or perf_event), > > > p->state is irrelevant to determine preemption. You can get preempted > > > with !task_is_running() just fine. > > > > > > The right indicator for preemption is if the task is still on the > > > runqueue in the sched-out path. > > > > > > Signed-off-by: Peter Zijlstra (Intel) > > > --- > > > kernel/events/core.c | 7 +++---- > > > virt/kvm/kvm_main.c | 2 +- > > > 2 files changed, 4 insertions(+), 5 deletions(-) > > > > > > --- a/kernel/events/core.c > > > +++ b/kernel/events/core.c > > > @@ -8568,13 +8568,12 @@ static void perf_event_switch(struct tas > > > }, > > > }; > > > > > > - if (!sched_in && task->state == TASK_RUNNING) > > > + if (!sched_in && current->on_rq) { > > > > This changes from checking task->state to current->on_rq, but this change > > from "task" to "current" is not described in the commit message, which is odd. > > > > Are we really sure that task == current here ? > > Yeah, @task == @prev == current at this point, but yes, not sure why I > changed that... lemme change that back to task. FWIW, with that: Acked-by: Mark Rutland I have no strong feelings either way w.r.t. the whitespace cleanup. ;) Thanks, Mark