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=-9.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,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 22B5CC433E7 for ; Tue, 13 Oct 2020 14:21:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A26BC24807 for ; Tue, 13 Oct 2020 14:21:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="dXm97LGy" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729795AbgJMOV1 (ORCPT ); Tue, 13 Oct 2020 10:21:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34788 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726822AbgJMOV1 (ORCPT ); Tue, 13 Oct 2020 10:21:27 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 35F3CC0613D0 for ; Tue, 13 Oct 2020 07:21:27 -0700 (PDT) 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=5X9x6sA1HPZKGi4HmuNe3XasDgdbZwe5ZtBJ6ONT/aY=; b=dXm97LGy0aiO1z3LlggPQV3BNo oesBHINUG7IKZoM5+rLhr9BwyI5vaNgdxmT8cuy87cBX+MGAc8/epryk0xFZc2rPKrxOC+WPSDfZU gyN0mFB97gzcQAnI5de907+pwCb1UgaGMSbcgs+qhcxgK6YcAV6cwzz9LUJzycLr7OPNn2VJ/ydlI 8+kc/8Gk3PIGWnChn1vIkXpHr1fvFYbNqM6jpj+PBovNcgeb/Z+n41MvAtTHBCB1LRoOOUybMo7ez w7pmWpqpHNdsAtacEobt09l5aptbEwY5d4CLWzMsCaZg3TdO6NLUUVYrvjKjWblQFucI601MjNL+o 4iNhD/hQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kSLAr-0004fO-0Z; Tue, 13 Oct 2020 14:21:09 +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 3CCDD301959; Tue, 13 Oct 2020 16:21:08 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 1DCAE2BFFEAE4; Tue, 13 Oct 2020 16:21:08 +0200 (CEST) Date: Tue, 13 Oct 2020 16:21:08 +0200 From: Peter Zijlstra To: Sebastian Andrzej Siewior Cc: Valentin Schneider , linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@kernel.org, qais.yousef@arm.com, swood@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vincent.donnefort@arm.com, tj@kernel.org Subject: Re: [PATCH 1/2] sched: Deny self-issued __set_cpus_allowed_ptr() when migrate_disable() Message-ID: <20201013142108.GD2594@hirez.programming.kicks-ass.net> References: <20201005145717.346020688@infradead.org> <20201013140116.26651-1-valentin.schneider@arm.com> <20201013141508.u7saiudjyuvihvcx@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201013141508.u7saiudjyuvihvcx@linutronix.de> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 13, 2020 at 04:15:08PM +0200, Sebastian Andrzej Siewior wrote: > On 2020-10-13 15:01:15 [+0100], Valentin Schneider wrote: > > migrate_disable(); > > set_cpus_allowed_ptr(current, {something excluding task_cpu(current)}); > > affine_move_task(); <-- never returns > > > > Signed-off-by: Valentin Schneider > > --- > > kernel/sched/core.c | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > > index 4ccd1099adaa..7f4e38819de1 100644 > > --- a/kernel/sched/core.c > > +++ b/kernel/sched/core.c > > @@ -2189,6 +2189,11 @@ static int __set_cpus_allowed_ptr(struct task_struct *p, > > if (!(flags & SCA_MIGRATE_ENABLE) && cpumask_equal(&p->cpus_mask, new_mask)) > > goto out; > > > > + if (p == current && > > + is_migration_disabled(p) && > > + !cpumask_test_cpu(task_cpu(p), new_mask)) > > + ret = -EBUSY; > > + > > This shouldn't happen, right? The function may sleep so it shouldn't be > entered with disabled migration. A WARN_ON might spot the bad caller. So yeah, I like detecting the case but agree with bigeasy that an additional WARN would make sense, lemme go add that.