From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754338AbcFPM5Z (ORCPT ); Thu, 16 Jun 2016 08:57:25 -0400 Received: from forward-corp1m.cmail.yandex.net ([5.255.216.100]:36105 "EHLO forward-corp1m.cmail.yandex.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753853AbcFPM5W (ORCPT ); Thu, 16 Jun 2016 08:57:22 -0400 Authentication-Results: smtpcorp1m.mail.yandex.net; dkim=pass header.i=@yandex-team.ru Subject: [PATCH] sched/fair: do not announce throttled next buddy in dequeue_task_fair From: Konstantin Khlebnikov To: Peter Zijlstra , Ingo Molnar , linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org Date: Thu, 16 Jun 2016 15:57:15 +0300 Message-ID: <146608183552.21905.15924473394414832071.stgit@buzz> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hierarchy could be already throttled at this point. Throttled next buddy could trigger null pointer dereference in pick_next_task_fair(). Signed-off-by: Konstantin Khlebnikov Cc: Stable # v3.2+ --- kernel/sched/fair.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index fe809fe169d2..3c6b038cb734 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4519,15 +4519,14 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags) /* Don't dequeue parent if it has other entities besides us */ if (cfs_rq->load.weight) { + /* avoid re-evaluating load for this entity */ + se = parent_entity(se); /* * Bias pick_next to pick a task from this cfs_rq, as * p is sleeping when it is within its sched_slice. */ - if (task_sleep && parent_entity(se)) - set_next_buddy(parent_entity(se)); - - /* avoid re-evaluating load for this entity */ - se = parent_entity(se); + if (task_sleep && se && !throttled_hierarchy(cfs_rq)) + set_next_buddy(se); break; } flags |= DEQUEUE_SLEEP;