linux-kernel - Re: [PATCH v8 7/8] sched/core: Prevent race condition between cpuset and __sched

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Message-ID: <20190702070111.GF26005@localhost.localdomain>
Date:   Tue, 2 Jul 2019 09:01:12 +0200
From:   Juri Lelli <juri.lelli@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     mingo@...hat.com, rostedt@...dmis.org, tj@...nel.org,
        linux-kernel@...r.kernel.org, luca.abeni@...tannapisa.it,
        claudio@...dence.eu.com, tommaso.cucinotta@...tannapisa.it,
        bristot@...hat.com, mathieu.poirier@...aro.org, lizefan@...wei.com,
        cgroups@...r.kernel.org
Subject: Re: [PATCH v8 7/8] sched/core: Prevent race condition between cpuset
 and __sched_setscheduler()

On 01/07/19 21:11, Peter Zijlstra wrote:
> On Fri, Jun 28, 2019 at 10:06:17AM +0200, Juri Lelli wrote:
> > No synchronisation mechanism exists 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.
> > 
> > Grab cpuset_rwsem read lock from core scheduler, so to prevent
> > situations such as the one described above from happening.
> > 
> 
> ISTR there being a funny vs normalize_rt_tasks(); maybe mention that?

Yep. I'll add a comment about it.