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Subject: Re: Deadlock due to "cpuset: Make cpuset hotplug synchronous"
From:   Qian Cai <cai@lca.pw>
In-Reply-To: <20200325191922.GM162390@mtj.duckdns.org>
Date:   Wed, 1 Apr 2020 22:00:31 -0400
Cc:     Prateek Sood <prsood@codeaurora.org>,
        Li Zefan <lizefan@huawei.com>, cgroups@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>
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 <20200325191922.GM162390@mtj.duckdns.org>
To:     Tejun Heo <tj@kernel.org>
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> On Mar 25, 2020, at 3:19 PM, Tejun Heo <tj@kernel.org> wrote:
>=20
> On Wed, Mar 25, 2020 at 03:16:56PM -0400, Qian Cai wrote:
>> The linux-next commit a49e4629b5ed (=E2=80=9Ccpuset: Make cpuset =
hotplug synchronous=E2=80=9D)
>> introduced real deadlocks with CPU hotplug as showed in the lockdep =
splat, since it is
>> now making a relation from cpu_hotplug_lock =E2=80=94> cgroup_mutex.
>=20
> 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.

Tejun, can you back off this commit now given it seems nobody is trying =
to rescue it?