Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755215AbaJ1LDL (ORCPT ); Tue, 28 Oct 2014 07:03:11 -0400 Received: from terminus.zytor.com ([198.137.202.10]:50904 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752636AbaJ1LDJ (ORCPT ); Tue, 28 Oct 2014 07:03:09 -0400 Date: Tue, 28 Oct 2014 04:02:07 -0700 From: tip-bot for Juri Lelli Message-ID: Cc: juri.lelli@arm.com, hpa@zytor.com, peterz@infradead.org, tglx@linutronix.de, michael@amarulasolutions.com, daniel.wagner@bmw-carit.de, mingo@kernel.org, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, raistlin@linux.it, fchecconi@gmail.com Reply-To: daniel.wagner@bmw-carit.de, michael@amarulasolutions.com, tglx@linutronix.de, hpa@zytor.com, juri.lelli@arm.com, peterz@infradead.org, fchecconi@gmail.com, torvalds@linux-foundation.org, raistlin@linux.it, linux-kernel@vger.kernel.org, mingo@kernel.org In-Reply-To: <1414142198-18552-5-git-send-email-juri.lelli@arm.com> References: <1414142198-18552-5-git-send-email-juri.lelli@arm.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] sched/deadline: Fix races between rt_mutex_setprio() and dl_task_timer() Git-Commit-ID: aee38ea95419c818dfdde52b115aeffe9cbb259b 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: aee38ea95419c818dfdde52b115aeffe9cbb259b Gitweb: http://git.kernel.org/tip/aee38ea95419c818dfdde52b115aeffe9cbb259b Author: Juri Lelli AuthorDate: Fri, 24 Oct 2014 10:16:38 +0100 Committer: Ingo Molnar CommitDate: Tue, 28 Oct 2014 10:46:01 +0100 sched/deadline: Fix races between rt_mutex_setprio() and dl_task_timer() dl_task_timer() is racy against several paths. Daniel noticed that the replenishment timer may experience a race condition against an enqueue_dl_entity() called from rt_mutex_setprio(). With his own words: rt_mutex_setprio() resets p->dl.dl_throttled. So the pattern is: start_dl_timer() throttled = 1, rt_mutex_setprio() throlled = 0, sched_switch() -> enqueue_task(), dl_task_timer-> enqueue_task() throttled is 0 => BUG_ON(on_dl_rq(dl_se)) fires as the scheduling entity is already enqueued on the -deadline runqueue. As we do for the other races, we just bail out in the replenishment timer code. Reported-by: Daniel Wagner Tested-by: Daniel Wagner Signed-off-by: Juri Lelli Signed-off-by: Peter Zijlstra (Intel) Cc: vincent@legout.info Cc: Dario Faggioli Cc: Michael Trimarchi Cc: Fabio Checconi Cc: Linus Torvalds Link: http://lkml.kernel.org/r/1414142198-18552-5-git-send-email-juri.lelli@arm.com Signed-off-by: Ingo Molnar --- kernel/sched/deadline.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 92279ea..4616789 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -518,12 +518,20 @@ again: } /* - * We need to take care of a possible races here. In fact, the - * task might have changed its scheduling policy to something - * different from SCHED_DEADLINE or changed its reservation - * parameters (through sched_setattr()). + * We need to take care of several possible races here: + * + * - the task might have changed its scheduling policy + * to something different than SCHED_DEADLINE + * - the task might have changed its reservation parameters + * (through sched_setattr()) + * - the task might have been boosted by someone else and + * might be in the boosting/deboosting path + * + * In all this cases we bail out, as the task is already + * in the runqueue or is going to be enqueued back anyway. */ - if (!dl_task(p) || dl_se->dl_new) + if (!dl_task(p) || dl_se->dl_new || + dl_se->dl_boosted || !dl_se->dl_throttled) goto unlock; sched_clock_tick(); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/