Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757656Ab3J2OIY (ORCPT ); Tue, 29 Oct 2013 10:08:24 -0400 Received: from terminus.zytor.com ([198.137.202.10]:45895 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932071Ab3J2OIT (ORCPT ); Tue, 29 Oct 2013 10:08:19 -0400 Date: Tue, 29 Oct 2013 07:07:49 -0700 From: tip-bot for Ben Segall Message-ID: Cc: linux-kernel@vger.kernel.org, bsegall@google.com, hpa@zytor.com, mingo@kernel.org, peterz@infradead.org, tglx@linutronix.de Reply-To: mingo@kernel.org, hpa@zytor.com, bsegall@google.com, linux-kernel@vger.kernel.org, peterz@infradead.org, tglx@linutronix.de In-Reply-To: <20131016181632.22647.84174.stgit@sword-of-the-dawn.mtv.corp.google.com> References: <20131016181632.22647.84174.stgit@sword-of-the-dawn.mtv.corp.google.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] sched: Avoid throttle_cfs_rq() racing with period_timer stopping Git-Commit-ID: f9f9ffc237dd924f048204e8799da74f9ecf40cf 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 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.1 (terminus.zytor.com [127.0.0.1]); Tue, 29 Oct 2013 07:07:55 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2878 Lines: 73 Commit-ID: f9f9ffc237dd924f048204e8799da74f9ecf40cf Gitweb: http://git.kernel.org/tip/f9f9ffc237dd924f048204e8799da74f9ecf40cf Author: Ben Segall AuthorDate: Wed, 16 Oct 2013 11:16:32 -0700 Committer: Ingo Molnar CommitDate: Tue, 29 Oct 2013 12:02:32 +0100 sched: Avoid throttle_cfs_rq() racing with period_timer stopping throttle_cfs_rq() doesn't check to make sure that period_timer is running, and while update_curr/assign_cfs_runtime does, a concurrently running period_timer on another cpu could cancel itself between this cpu's update_curr and throttle_cfs_rq(). If there are no other cfs_rqs running in the tg to restart the timer, this causes the cfs_rq to be stranded forever. Fix this by calling __start_cfs_bandwidth() in throttle if the timer is inactive. (Also add some sched_debug lines for cfs_bandwidth.) Tested: make a run/sleep task in a cgroup, loop switching the cgroup between 1ms/100ms quota and unlimited, checking for timer_active=0 and throttled=1 as a failure. With the throttle_cfs_rq() change commented out this fails, with the full patch it passes. Signed-off-by: Ben Segall Signed-off-by: Peter Zijlstra Cc: pjt@google.com Link: http://lkml.kernel.org/r/20131016181632.22647.84174.stgit@sword-of-the-dawn.mtv.corp.google.com Signed-off-by: Ingo Molnar --- kernel/sched/debug.c | 8 ++++++++ kernel/sched/fair.c | 2 ++ 2 files changed, 10 insertions(+) diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index e6ba5e3..5c34d18 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -229,6 +229,14 @@ void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq) atomic_read(&cfs_rq->tg->runnable_avg)); #endif #endif +#ifdef CONFIG_CFS_BANDWIDTH + SEQ_printf(m, " .%-30s: %d\n", "tg->cfs_bandwidth.timer_active", + cfs_rq->tg->cfs_bandwidth.timer_active); + SEQ_printf(m, " .%-30s: %d\n", "throttled", + cfs_rq->throttled); + SEQ_printf(m, " .%-30s: %d\n", "throttle_count", + cfs_rq->throttle_count); +#endif #ifdef CONFIG_FAIR_GROUP_SCHED print_cfs_group_stats(m, cpu, cfs_rq->tg); diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 0923ab2..41c02b6 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3112,6 +3112,8 @@ static void throttle_cfs_rq(struct cfs_rq *cfs_rq) cfs_rq->throttled_clock = rq_clock(rq); raw_spin_lock(&cfs_b->lock); list_add_tail_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq); + if (!cfs_b->timer_active) + __start_cfs_bandwidth(cfs_b); raw_spin_unlock(&cfs_b->lock); } -- 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/