Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754265AbaANA33 (ORCPT ); Mon, 13 Jan 2014 19:29:29 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:54515 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754076AbaANA3E (ORCPT ); Mon, 13 Jan 2014 19:29:04 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Ben Segall , Peter Zijlstra , pjt@google.com, Ingo Molnar , Chris J Arges Subject: [PATCH 3.12 74/77] sched: Fix race on toggling cfs_bandwidth_used Date: Mon, 13 Jan 2014 16:28:35 -0800 Message-Id: <20140114002754.591291400@linuxfoundation.org> X-Mailer: git-send-email 1.8.5.1.163.gd7aced9 In-Reply-To: <20140114002752.497010554@linuxfoundation.org> References: <20140114002752.497010554@linuxfoundation.org> User-Agent: quilt/0.61-1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ben Segall commit 1ee14e6c8cddeeb8a490d7b54cd9016e4bb900b4 upstream. When we transition cfs_bandwidth_used to false, any currently throttled groups will incorrectly return false from cfs_rq_throttled. While tg_set_cfs_bandwidth will unthrottle them eventually, currently running code (including at least dequeue_task_fair and distribute_cfs_runtime) will cause errors. Fix this by turning off cfs_bandwidth_used only after unthrottling all cfs_rqs. Tested: toggle bandwidth back and forth on a loaded cgroup. Caused crashes in minutes without the patch, hasn't crashed with it. Signed-off-by: Ben Segall Signed-off-by: Peter Zijlstra Cc: pjt@google.com Link: http://lkml.kernel.org/r/20131016181611.22647.80365.stgit@sword-of-the-dawn.mtv.corp.google.com Signed-off-by: Ingo Molnar Cc: Chris J Arges Signed-off-by: Greg Kroah-Hartman --- kernel/sched/core.c | 9 ++++++++- kernel/sched/fair.c | 16 +++++++++------- kernel/sched/sched.h | 3 ++- 3 files changed, 19 insertions(+), 9 deletions(-) --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7277,7 +7277,12 @@ static int tg_set_cfs_bandwidth(struct t runtime_enabled = quota != RUNTIME_INF; runtime_was_enabled = cfs_b->quota != RUNTIME_INF; - account_cfs_bandwidth_used(runtime_enabled, runtime_was_enabled); + /* + * If we need to toggle cfs_bandwidth_used, off->on must occur + * before making related changes, and on->off must occur afterwards + */ + if (runtime_enabled && !runtime_was_enabled) + cfs_bandwidth_usage_inc(); raw_spin_lock_irq(&cfs_b->lock); cfs_b->period = ns_to_ktime(period); cfs_b->quota = quota; @@ -7303,6 +7308,8 @@ static int tg_set_cfs_bandwidth(struct t unthrottle_cfs_rq(cfs_rq); raw_spin_unlock_irq(&rq->lock); } + if (runtime_was_enabled && !runtime_enabled) + cfs_bandwidth_usage_dec(); out_unlock: mutex_unlock(&cfs_constraints_mutex); --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2077,13 +2077,14 @@ static inline bool cfs_bandwidth_used(vo return static_key_false(&__cfs_bandwidth_used); } -void account_cfs_bandwidth_used(int enabled, int was_enabled) +void cfs_bandwidth_usage_inc(void) { - /* only need to count groups transitioning between enabled/!enabled */ - if (enabled && !was_enabled) - static_key_slow_inc(&__cfs_bandwidth_used); - else if (!enabled && was_enabled) - static_key_slow_dec(&__cfs_bandwidth_used); + static_key_slow_inc(&__cfs_bandwidth_used); +} + +void cfs_bandwidth_usage_dec(void) +{ + static_key_slow_dec(&__cfs_bandwidth_used); } #else /* HAVE_JUMP_LABEL */ static bool cfs_bandwidth_used(void) @@ -2091,7 +2092,8 @@ static bool cfs_bandwidth_used(void) return true; } -void account_cfs_bandwidth_used(int enabled, int was_enabled) {} +void cfs_bandwidth_usage_inc(void) {} +void cfs_bandwidth_usage_dec(void) {} #endif /* HAVE_JUMP_LABEL */ /* --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1305,7 +1305,8 @@ extern void print_rt_stats(struct seq_fi extern void init_cfs_rq(struct cfs_rq *cfs_rq); extern void init_rt_rq(struct rt_rq *rt_rq, struct rq *rq); -extern void account_cfs_bandwidth_used(int enabled, int was_enabled); +extern void cfs_bandwidth_usage_inc(void); +extern void cfs_bandwidth_usage_dec(void); #ifdef CONFIG_NO_HZ_COMMON enum rq_nohz_flag_bits { -- 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/