linux-kernel - Re: [PATCH] cgroup/cpuset: remove circular dependency deadlock

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Message-ID: <20171025093041.GO3165@worktop.lehotels.local>
Date:   Wed, 25 Oct 2017 11:30:41 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Prateek Sood <prsood@...eaurora.org>
Cc:     tj@...nel.org, lizefan@...wei.com, cgroups@...r.kernel.org,
        mingo@...nel.org, longman@...hat.com, boqun.feng@...il.com,
        tglx@...utronix.de, linux-kernel@...r.kernel.org,
        sramana@...eaurora.org
Subject: Re: [PATCH] cgroup/cpuset: remove circular dependency deadlock

On Wed, Oct 25, 2017 at 02:09:54PM +0530, Prateek Sood wrote:
> >  void cpuset_update_active_cpus(void)
> >  {
> > +	mutex_lock(&cpuset_mutex);
> > +	rebuild_sched_domains_cpuslocked();
> > +	mutex_unlock(&cpuset_mutex);
> >  }
> 
> In the above patch rebuild_sched_domains_cpuslocked() has been
> used directly. Earlier cpuset_hotplug_update_tasks() was also
> called from cpuset_hotplug_workfn(). So migration of tasks
> related to cgroup which has empty cpuset would not happen
> during cpu hotplug.
> 
> 
> Could you please help in understanding more on this.
> 

That was me being lazy...