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=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_NONE,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 EAD4BC47093 for ; Wed, 2 Jun 2021 13:59:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D179B613E4 for ; Wed, 2 Jun 2021 13:59:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230062AbhFBOAy (ORCPT ); Wed, 2 Jun 2021 10:00:54 -0400 Received: from mail.efficios.com ([167.114.26.124]:35170 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230004AbhFBOAx (ORCPT ); Wed, 2 Jun 2021 10:00:53 -0400 Received: from localhost (localhost [127.0.0.1]) by mail.efficios.com (Postfix) with ESMTP id BC760302ADD; Wed, 2 Jun 2021 09:59:08 -0400 (EDT) Received: from mail.efficios.com ([127.0.0.1]) by localhost (mail03.efficios.com [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id 0NlAF8aaNhCD; Wed, 2 Jun 2021 09:59:08 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mail.efficios.com (Postfix) with ESMTP id 2A108302BA9; Wed, 2 Jun 2021 09:59:08 -0400 (EDT) DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com 2A108302BA9 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=default; t=1622642348; bh=3NQkpeJ7B+hKtKJgR6oI37w8WcTETaBafQ5/DPMEWwI=; h=Date:From:To:Message-ID:MIME-Version; b=ZlLvrNpb7FSQdBC5tIEKb93seCOYMQlGgXqNDCt4mx931pzNw8PkQPGTIAknvIKON NpDSBJXZebM5bdDBEXJUhkVKv214RxCfD9cnMAu+E9jlJUbxCT0sSH9pfYpV4sduq4 x3/Ha4HOzhfJ5u6uVpyJg0D3SZEpnzu++L3CaXS5k4TUIGuZ+VTcOcX9C3+gYxGHL4 vP87muDZtj763iw70P68DkCsJf/o77PvwVPhmezDZ6qbVfVNe7D4w95pMohMEmylCc wLPLpR4HOsL54+3PlAjOEK3N1Uw5WtMxdLnoo8ef/7RMfiFuOK3kBtQodyzCCa6QyK u+WAXvtkoLOCw== X-Virus-Scanned: amavisd-new at efficios.com Received: from mail.efficios.com ([127.0.0.1]) by localhost (mail03.efficios.com [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id 6rM4q68lPaCz; Wed, 2 Jun 2021 09:59:08 -0400 (EDT) Received: from mail03.efficios.com (mail03.efficios.com [167.114.26.124]) by mail.efficios.com (Postfix) with ESMTP id 00C463028D6; Wed, 2 Jun 2021 09:59:08 -0400 (EDT) Date: Wed, 2 Jun 2021 09:59:07 -0400 (EDT) From: Mathieu Desnoyers To: Peter Zijlstra Cc: 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 , Mark Rutland , 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 Message-ID: <1873020549.5854.1622642347895.JavaMail.zimbra@efficios.com> In-Reply-To: <20210602133040.398289363@infradead.org> References: <20210602131225.336600299@infradead.org> <20210602133040.398289363@infradead.org> Subject: Re: [PATCH 3/6] sched,perf,kvm: Fix preemption condition MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [167.114.26.124] X-Mailer: Zimbra 8.8.15_GA_4018 (ZimbraWebClient - FF88 (Linux)/8.8.15_GA_4026) Thread-Topic: sched,perf,kvm: Fix preemption condition Thread-Index: r+iuleOU2QevO+uazLhH122pXkMx7g== Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org ----- 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 ? Thanks, Mathieu > switch_event.event_id.header.misc |= > PERF_RECORD_MISC_SWITCH_OUT_PREEMPT; > + } > > - perf_iterate_sb(perf_event_switch_output, > - &switch_event, > - NULL); > + perf_iterate_sb(perf_event_switch_output, &switch_event, NULL); > } > > /* > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -4869,7 +4869,7 @@ static void kvm_sched_out(struct preempt > { > struct kvm_vcpu *vcpu = preempt_notifier_to_vcpu(pn); > > - if (current->state == TASK_RUNNING) { > + if (current->on_rq) { > WRITE_ONCE(vcpu->preempted, true); > WRITE_ONCE(vcpu->ready, true); > } -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com