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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 71BCECA9ECB for ; Thu, 31 Oct 2019 14:25:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4F25D2083E for ; Thu, 31 Oct 2019 14:25:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728168AbfJaOZG (ORCPT ); Thu, 31 Oct 2019 10:25:06 -0400 Received: from foss.arm.com ([217.140.110.172]:49428 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727705AbfJaOZE (ORCPT ); Thu, 31 Oct 2019 10:25:04 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 621671F1; Thu, 31 Oct 2019 07:25:04 -0700 (PDT) Received: from [172.20.53.248] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B183F3F71E; Thu, 31 Oct 2019 07:25:00 -0700 (PDT) Subject: Re: NULL pointer dereference in pick_next_task_fair From: Valentin Schneider To: Ram Muthiah , Quentin Perret Cc: Peter Zijlstra , 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 References: <20191028174603.GA246917@google.com> <20191029113411.GP4643@worktop.programming.kicks-ass.net> <20191029115000.GA11194@google.com> <75e99374-0bd6-a7d7-581e-9360a1f90103@arm.com> <8d8fe4e9-1905-cde1-9ced-0a860e5a961b@arm.com> Message-ID: <4f743a74-9b9c-d7e4-bae8-c7ad1d2aeee6@arm.com> Date: Thu, 31 Oct 2019 15:24:55 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <8d8fe4e9-1905-cde1-9ced-0a860e5a961b@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 31/10/2019 11:54, Valentin Schneider wrote: > On 31/10/2019 02:33, Valentin Schneider wrote: >> For wakeups, select_task_rq_fair() can only ever pick prev_cpu or this_cpu >> since there are no sched domains. I don't see many candidates that could >> wakeup on a secondary (thus have non-zero this_cpu) this early there. And another fail here, this doesn't have to be at secondary bringup, it's just that the bringup will always be in the idle task's callstack (if the timestamps weren't enough of a clue already). I guess I'll stop writing nonsense and keep staring in silence.