From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752057AbdFTNba (ORCPT ); Tue, 20 Jun 2017 09:31:30 -0400 Received: from terminus.zytor.com ([65.50.211.136]:38875 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751927AbdFTNb2 (ORCPT ); Tue, 20 Jun 2017 09:31:28 -0400 Date: Tue, 20 Jun 2017 06:26:51 -0700 From: tip-bot for Daniel Axtens Message-ID: Cc: peterz@infradead.org, khlebnikov@yandex-team.ru, bsegall@google.com, mingo@kernel.org, efault@gmx.de, hpa@zytor.com, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, dja@axtens.net, tglx@linutronix.de Reply-To: linux-kernel@vger.kernel.org, hpa@zytor.com, efault@gmx.de, tglx@linutronix.de, dja@axtens.net, torvalds@linux-foundation.org, khlebnikov@yandex-team.ru, bsegall@google.com, peterz@infradead.org, mingo@kernel.org In-Reply-To: <20170510201139.16236-1-dja@axtens.net> References: <20170510201139.16236-1-dja@axtens.net> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] sched/fair: WARN() and refuse to set buddy when !se->on_rq Git-Commit-ID: c5ae366e12b2bd56fc7d7e9d484836bec9ddc110 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: c5ae366e12b2bd56fc7d7e9d484836bec9ddc110 Gitweb: http://git.kernel.org/tip/c5ae366e12b2bd56fc7d7e9d484836bec9ddc110 Author: Daniel Axtens AuthorDate: Thu, 11 May 2017 06:11:39 +1000 Committer: Ingo Molnar CommitDate: Tue, 20 Jun 2017 12:26:52 +0200 sched/fair: WARN() and refuse to set buddy when !se->on_rq If we set a next or last buddy for a se that is not on_rq, we will end up taking a NULL pointer dereference in wakeup_preempt_entity via pick_next_task_fair. Detect when we would be about to do that, throw a warning and then refuse to actually set it. This has been suggested at least twice: https://marc.info/?l=linux-kernel&m=146651668921468&w=2 https://lkml.org/lkml/2016/6/16/663 I recently had to debug a problem with these (we hadn't backported Konstantin's patches in this area) and this would have saved a lot of time/pain. Just do it. Signed-off-by: Daniel Axtens Cc: Ben Segall Cc: Konstantin Khlebnikov Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20170510201139.16236-1-dja@axtens.net Signed-off-by: Ingo Molnar --- kernel/sched/fair.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 396bca9..cb3a3da 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6164,8 +6164,11 @@ static void set_last_buddy(struct sched_entity *se) if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE)) return; - for_each_sched_entity(se) + for_each_sched_entity(se) { + if (SCHED_WARN_ON(!se->on_rq)) + return; cfs_rq_of(se)->last = se; + } } static void set_next_buddy(struct sched_entity *se) @@ -6173,8 +6176,11 @@ static void set_next_buddy(struct sched_entity *se) if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE)) return; - for_each_sched_entity(se) + for_each_sched_entity(se) { + if (SCHED_WARN_ON(!se->on_rq)) + return; cfs_rq_of(se)->next = se; + } } static void set_skip_buddy(struct sched_entity *se)