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=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 BC31CC4708F for ; Wed, 2 Jun 2021 14:12:52 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 6EDEE6141C for ; Wed, 2 Jun 2021 14:12:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6EDEE6141C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 8831A8E002F; Wed, 2 Jun 2021 10:12:26 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 85B158E002C; Wed, 2 Jun 2021 10:12:26 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 686268E002F; Wed, 2 Jun 2021 10:12:26 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0247.hostedemail.com [216.40.44.247]) by kanga.kvack.org (Postfix) with ESMTP id 311BD8E002C for ; Wed, 2 Jun 2021 10:12:26 -0400 (EDT) Received: from smtpin04.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id BC24882499A8 for ; Wed, 2 Jun 2021 14:12:25 +0000 (UTC) X-FDA: 78208973850.04.B8887D5 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf03.hostedemail.com (Postfix) with ESMTP id 2B52AC00CBF4 for ; Wed, 2 Jun 2021 14:12:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; 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=Sziljs0Kulfo1/57Liy6kTpQt/mrzjVM95lhyl4pzA4=; b=di9dQnw7YWomw7sRDOsQo7PUMD TJInYkPIDn+/QK90Sos0c8Rezc7X8ImBRnaDqxkesZTzU3zBWgy4G6U4xXqLz09/hpYATAA8slRuH z5QgLBkbaBJf/nxSrsbFRF31HH3ARg56XBhL22G9hLm1sHL0quLpRuKbqF/t2jaxsG2aoKnSpz0J6 JwRCyVRR/4oZYywGxUDYGOan1B+cIaFO1YcfQl0rAlpcHTiWKkj2/IJRMvkKXL0znHPsw7bjE4bnM 9Z7WPFFotrWHc/x+VwwKdH54p9rhGCj4A2ocBzrxy0h4dJrMU7v/Kb9Xu0TyOL8TyMumyZPfiWVKG NNissGXA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94 #2 (Red Hat Linux)) id 1loRZn-00BBJ8-0J; Wed, 02 Jun 2021 14:10:35 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 27D8F30008D; Wed, 2 Jun 2021 16:10:29 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 10B2A20223DA5; Wed, 2 Jun 2021 16:10:29 +0200 (CEST) Date: Wed, 2 Jun 2021 16:10:29 +0200 From: Peter Zijlstra To: Mathieu Desnoyers 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 Subject: Re: [PATCH 3/6] sched,perf,kvm: Fix preemption condition Message-ID: 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: <1873020549.5854.1622642347895.JavaMail.zimbra@efficios.com> Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=di9dQnw7; dmarc=none; spf=none (imf03.hostedemail.com: domain of peterz@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=peterz@infradead.org X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 2B52AC00CBF4 X-Stat-Signature: 4er3755unf5i7k6mwp47ap7siaipbett X-HE-Tag: 1622643132-473119 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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.