linux-kernel - Re: Deadlock due to "cpuset: Make cpuset hotplug synchronous"

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Date:   Thu, 26 Mar 2020 10:15:32 +0000
From:   Qais Yousef <qais.yousef@....com>
To:     Tejun Heo <tj@...nel.org>
Cc:     Qian Cai <cai@....pw>, Prateek Sood <prsood@...eaurora.org>,
        Li Zefan <lizefan@...wei.com>, cgroups@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: Deadlock due to "cpuset: Make cpuset hotplug synchronous"

On 03/25/20 15:19, Tejun Heo wrote:
> On Wed, Mar 25, 2020 at 03:16:56PM -0400, Qian Cai wrote:
> > The linux-next commit a49e4629b5ed (“cpuset: Make cpuset hotplug synchronous”)
> > introduced real deadlocks with CPU hotplug as showed in the lockdep splat, since it is
> > now making a relation from cpu_hotplug_lock —> cgroup_mutex.
> 
> Prateek, can you please take a look? Given that the merge window is just around
> the corner, we might have to revert and retry later if it can't be resolved
> quickly.

I've ran cpuset_hotplug and cpuhotplug LTP tests using next-20200325 but
couldn't reproduce it.

Hopefully that can be fixed, but if you had to revert it, do you mind picking
this instead to fix the LTP issue I encountered before?

	https://lore.kernel.org/lkml/20200211141554.24181-1-qais.yousef@arm.com/

Thanks!

--
Qais Yousef