From mboxrd@z Thu Jan 1 00:00:00 1970 From: Juri Lelli Subject: Re: [PATCH V3 04/10] sched/core: Prevent race condition between cpuset and __sched_setscheduler() Date: Wed, 14 Feb 2018 11:36:39 +0100 Message-ID: <20180214103639.GR12979@localhost.localdomain> References: <1518553967-20656-1-git-send-email-mathieu.poirier@linaro.org> <1518553967-20656-5-git-send-email-mathieu.poirier@linaro.org> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <1518553967-20656-5-git-send-email-mathieu.poirier@linaro.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Mathieu Poirier Cc: peterz@infradead.org, lizefan@huawei.com, mingo@redhat.com, rostedt@goodmis.org, claudio@evidence.eu.com, bristot@redhat.com, tommaso.cucinotta@santannapisa.it, luca.abeni@santannapisa.it, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Hi Mathieu, On 13/02/18 13:32, Mathieu Poirier wrote: > 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 > --- [...] > 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(); > + > + /* Mmm, I'm afraid we can't do this. __sched_setscheduler might be called from interrupt contex by normalize_rt_tasks(). Best, - Juri