Re: [PATCH] cpusets: fix deadlock with cpu_down()->cpuset_lock()

[Oleg Nesterov]

On 07/29, Oleg Nesterov wrote:
>
> I strongly believe the bug does exist, but this patch needs the review
> from maintainers.

Yes...

> IOW, with this patch migration_call(CPU_DEAD) runs without callback_mutex,
> but kernel/cpuset.c always takes get_online_cpus() before callback_mutex.

Oh. I'm afraid this is not an option.

callback_mutex should nest under cgroup_mutex, but cpu hotplu pathes
take cgroup_mutex under cpu_hotplug->lock. Lockdep won't be happy.

Oleg.

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