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=-6.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 E009EC2D0E4 for ; Tue, 17 Nov 2020 11:06:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 582D72078E for ; Tue, 17 Nov 2020 11:06:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="u8kf7c54" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728437AbgKQLGo (ORCPT ); Tue, 17 Nov 2020 06:06:44 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38712 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728362AbgKQLGo (ORCPT ); Tue, 17 Nov 2020 06:06:44 -0500 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 806BCC0613CF; Tue, 17 Nov 2020 03:06:43 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.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=BRrBBz1KgvikzkccKqFTVSAPFjaDPkfexbTOVrIOZI8=; b=u8kf7c54YIWfDuyxYoHulRHvoS h0L8H4TE1o3yzAlu35DwMUMyAql7jIOPyCMJ8/V3Nii5adSvXvbWwcNrGoTFGaKnB522jlan70HxA 0/jh5hu/bWr1ulwp74ouOm4lEY5raFw0z9armYVRw98qK0EBvFzp2TQGnf9uhZua/Zs5Ko0tji9GN H1QhGjaeQ1HJdPkLHoyaSfzMIRcq8XoZ4dfRGveCIBN7FtM/iIz4IM95gHu8juWLdoKe0knSW/csN jbHra8ntqpMv9Z1Bso3KGEAxUWAbZEabelzXjZi3sOIhezFPdvF8W2txAgmwK01hUu1IS1e4jgTAN j4r/gbaA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1keyob-0001aY-65; Tue, 17 Nov 2020 11:06:25 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id B29BD305CC3; Tue, 17 Nov 2020 12:06:20 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 987F720159855; Tue, 17 Nov 2020 12:06:20 +0100 (CET) Date: Tue, 17 Nov 2020 12:06:20 +0100 From: Peter Zijlstra To: Valentin Schneider Cc: Oleksandr Natalenko , linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, rostedt@goodmis.org Subject: Re: WARNING at kernel/sched/core.c:2013 migration_cpu_stop+0x2e3/0x330 Message-ID: <20201117110620.GG3121378@hirez.programming.kicks-ass.net> References: 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-kernel@vger.kernel.org On Mon, Nov 16, 2020 at 10:00:14AM +0000, Valentin Schneider wrote: > > On 15/11/20 22:32, Oleksandr Natalenko wrote: > > Hi. > > > > I'm running v5.10-rc3-rt7 for some time, and I came across this splat in > > dmesg: > > > > ``` > > [118769.951010] ------------[ cut here ]------------ > > [118769.951013] WARNING: CPU: 19 PID: 146 at kernel/sched/core.c:2013 > > Err, I didn't pick up on this back then, but isn't that check bogus? If the > task is enqueued elsewhere, it's valid for it not to be affined > 'here'. Also that is_migration_disabled() check within is_cpu_allowed() > makes me think this isn't the best thing to call on a remote task. > > --- > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 1218f3ce1713..47d5b677585f 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -2010,7 +2010,7 @@ static int migration_cpu_stop(void *data) > * valid again. Nothing to do. > */ > if (!pending) { > - WARN_ON_ONCE(!is_cpu_allowed(p, cpu_of(rq))); > + WARN_ON_ONCE(!cpumask_test_cpu(task_cpu(p), p->cpus_ptr)); Ho humm.. bit of a mess that. I'm trying to figure out if we need that is_per_cpu_kthread() test here or not. I suppose not, what we want here is to ensure the CPU is in cpus_mask and not care about the whole hotplug mess. Would it makes sense to replace both instances in migration_cpu_stop() with: WARN_ON_ONCE(!cpumask_test_cpu(task_cpu(p), p->cpus_mask)); ?