From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965918AbeBMUe5 (ORCPT ); Tue, 13 Feb 2018 15:34:57 -0500 Received: from mail-pg0-f66.google.com ([74.125.83.66]:33687 "EHLO mail-pg0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965795AbeBMUc5 (ORCPT ); Tue, 13 Feb 2018 15:32:57 -0500 X-Google-Smtp-Source: AH8x225J4cXK9g754aUYoS14hprrd5VSeNPQgr4FMQ5I86ld/lCm//ryLUa8RS3iLWOWOMYj3L4cIg== From: Mathieu Poirier To: peterz@infradead.org Cc: lizefan@huawei.com, mingo@redhat.com, rostedt@goodmis.org, claudio@evidence.eu.com, bristot@redhat.com, tommaso.cucinotta@santannapisa.it, juri.lelli@redhat.com, luca.abeni@santannapisa.it, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH V3 04/10] sched/core: Prevent race condition between cpuset and __sched_setscheduler() Date: Tue, 13 Feb 2018 13:32:41 -0700 Message-Id: <1518553967-20656-5-git-send-email-mathieu.poirier@linaro.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1518553967-20656-1-git-send-email-mathieu.poirier@linaro.org> References: <1518553967-20656-1-git-send-email-mathieu.poirier@linaro.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org No synchronisation mechanism exist between the cpuset subsystem and calls to function __sched_setscheduler(). As such it is possible that new root domains are created on the cpuset side while a deadline acceptance test is carried out in __sched_setscheduler(), leading to a potential oversell of CPU bandwidth. By making available the cpuset_mutex to the core scheduler it is possible to prevent situations such as the one described above from happening. Signed-off-by: Mathieu Poirier --- include/linux/cpuset.h | 6 ++++++ kernel/cgroup/cpuset.c | 16 ++++++++++++++++ kernel/sched/core.c | 9 +++++++++ 3 files changed, 31 insertions(+) diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h index 934633a05d20..4bbb3f5a3020 100644 --- a/include/linux/cpuset.h +++ b/include/linux/cpuset.h @@ -55,6 +55,8 @@ extern void cpuset_init_smp(void); extern void cpuset_force_rebuild(void); extern void cpuset_update_active_cpus(void); extern void cpuset_wait_for_hotplug(void); +extern void cpuset_lock(void); +extern void cpuset_unlock(void); extern void cpuset_cpus_allowed(struct task_struct *p, struct cpumask *mask); extern void cpuset_cpus_allowed_fallback(struct task_struct *p); extern nodemask_t cpuset_mems_allowed(struct task_struct *p); @@ -176,6 +178,10 @@ static inline void cpuset_update_active_cpus(void) static inline void cpuset_wait_for_hotplug(void) { } +static inline void cpuset_lock(void) { } + +static inline void cpuset_unlock(void) { } + static inline void cpuset_cpus_allowed(struct task_struct *p, struct cpumask *mask) { diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index d18c72e83de4..41f8391640e6 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -2410,6 +2410,22 @@ void __init cpuset_init_smp(void) } /** + * cpuset_lock - Grab the cpuset_mutex from another subsysytem + */ +void cpuset_lock(void) +{ + mutex_lock(&cpuset_mutex); +} + +/** + * cpuset_unlock - Release the cpuset_mutex from another subsysytem + */ +void cpuset_unlock(void) +{ + mutex_unlock(&cpuset_mutex); +} + +/** * cpuset_cpus_allowed - return cpus_allowed mask from a tasks cpuset. * @tsk: pointer to task_struct from which to obtain cpuset->cpus_allowed. * @pmask: pointer to struct cpumask variable to receive cpus_allowed set. diff --git a/kernel/sched/core.c b/kernel/sched/core.c index f727c3d0064c..0d8badcf1f0f 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4176,6 +4176,13 @@ static int __sched_setscheduler(struct task_struct *p, } /* + * Make sure we don't race with the cpuset subsystem where root + * domains can be rebuilt or modified while operations like DL + * admission checks are carried out. + */ + cpuset_lock(); + + /* * Make sure no PI-waiters arrive (or leave) while we are * changing the priority of the task: * @@ -4247,6 +4254,7 @@ static int __sched_setscheduler(struct task_struct *p, if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) { policy = oldpolicy = -1; task_rq_unlock(rq, p, &rf); + cpuset_unlock(); goto recheck; } @@ -4316,6 +4324,7 @@ static int __sched_setscheduler(struct task_struct *p, unlock: task_rq_unlock(rq, p, &rf); + cpuset_unlock(); return retval; } -- 2.7.4