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=-6.6 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FSL_HELO_FAKE,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1, USER_IN_DEF_DKIM_WL 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 916A8FA372C for ; Fri, 8 Nov 2019 11:58:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 64227207FA for ; Fri, 8 Nov 2019 11:58:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="cgRYI/7o" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391377AbfKHL6U (ORCPT ); Fri, 8 Nov 2019 06:58:20 -0500 Received: from mail-wr1-f47.google.com ([209.85.221.47]:37204 "EHLO mail-wr1-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390905AbfKHL6S (ORCPT ); Fri, 8 Nov 2019 06:58:18 -0500 Received: by mail-wr1-f47.google.com with SMTP id t1so6769292wrv.4 for ; Fri, 08 Nov 2019 03:58:16 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=gBB8RdG6cgVejm1+1f0yeucdoAW2HER5z2jtyPd3g1s=; b=cgRYI/7ou22BR4kVltlnBBqDlFDI8Gp8MkNZ/DQMG60IrDnEcssQ3nKLDVfFqDttj4 Veqi2doC2GQqFzsAJMytjBUnMLqlPKqiI4KE12zjihv09FAQw+23SOeSnUUuZrrBcuMH FlamaHpcJHV3y+uvmM/7AmG/2vEmJD8o7QAeZmEEUlkMVe0Df6MxppiAIYqf61xuKw/G 18Rte3s+bcF08katymvpVw7qh1aYJpze6r2dNVvvJFDlFxYsFjHbXUSioSaKpSOV6Svi +8TwHoz1/ZazR9+a+K/Gn94RBWUqI3x3Yxc4RG7nr1N4qlkFGBL1y486ENh+V6VGO/DD 0J8A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=gBB8RdG6cgVejm1+1f0yeucdoAW2HER5z2jtyPd3g1s=; b=CjyTw6DJENNEqdAxI/PYBa/0N+IbsasJl43HbgQ3ENRBZQ0tO5rv1y+QIOqqPfvXEd IeuRW2TBFtxpdSSXs9k8o8eG+dMv2cYldoOnWADha+SkIcE/jMj36fZQ47NHBYWOXCsv 5509b7cCiKXPsMo/5/2RD/XsixqfR8RpUwEvA68sD45iY/iUq4q+s2V9Buz7Mjr1Wval NywaM9vxfPOcjE24RzdIBm1YVJztKnQLLbevYrtvitiEzkOldjBpY9T7zBLglvHLkt0l AsdytwDWpRoWILOwe6fCr57m7WjoaLV9A2O8zZFqauMu6XmkUfE9NMZkcUaad7LOCMyX /0vA== X-Gm-Message-State: APjAAAVPn30jd5d3qvvFC3yofyBEVVU8kx0UXFw9OCfngoth9BtZ15S6 qGavw9K3jppg9ziN5vcJitCuDQ== X-Google-Smtp-Source: APXvYqyC9pw8OUJYHk/j0p9Odwzfg/Zr0rBxQNKGI7+vHgVIkdRqX8ubKPLeTAt2u6DNzu6GVvtCrw== X-Received: by 2002:a05:6000:350:: with SMTP id e16mr8631754wre.276.1573214295884; Fri, 08 Nov 2019 03:58:15 -0800 (PST) Received: from google.com ([2a00:79e0:d:110:d6cc:2030:37c1:9964]) by smtp.gmail.com with ESMTPSA id v8sm8734669wra.79.2019.11.08.03.58.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 08 Nov 2019 03:58:13 -0800 (PST) Date: Fri, 8 Nov 2019 11:58:10 +0000 From: Quentin Perret To: Valentin Schneider Cc: Peter Zijlstra , Kirill Tkhai , linux-kernel@vger.kernel.org, aaron.lwe@gmail.com, mingo@kernel.org, pauld@redhat.com, jdesfossez@digitalocean.com, naravamudan@digitalocean.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, juri.lelli@redhat.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, kernel-team@android.com, john.stultz@linaro.org Subject: Re: NULL pointer dereference in pick_next_task_fair Message-ID: <20191108115810.GA83597@google.com> References: <33643a5b-1b83-8605-2347-acd1aea04f93@virtuozzo.com> <20191106165437.GX4114@hirez.programming.kicks-ass.net> <20191106172737.GM5671@hirez.programming.kicks-ass.net> <831c2cd4-40a4-31b2-c0aa-b5f579e770d6@virtuozzo.com> <20191107132628.GZ4114@hirez.programming.kicks-ass.net> <20191107153848.GA31774@google.com> <20191107184356.GF4114@hirez.programming.kicks-ass.net> <20191107192907.GA30258@worktop.programming.kicks-ass.net> <20191108110212.GA204618@google.com> <07d30588-22e6-e098-b591-29c7cd3c8054@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <07d30588-22e6-e098-b591-29c7cd3c8054@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Friday 08 Nov 2019 at 11:47:44 (+0000), Valentin Schneider wrote: > I think we can ignore RETRY_TASK because this happens before the picking loop, > so we'll observe any new DL/RT task that got enqueued while newidle released > the lock. This also means we can safely break the balance loop in > pick_next_task() when we get RETRY_TASK, because we've got something to pick > (some new RT/DL task). Ah right, the second loop always iterates from DL, so that works. > This wants a comment though, methinks. +1 :) Thanks, Quentin