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Date: Wed, 8 Feb 2017 09:06:47 -0600 (CST)
From: Christoph Lameter <cl@linux.com>
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To: Thomas Gleixner <tglx@linutronix.de>
cc: Michal Hocko <mhocko@kernel.org>,
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        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: mm: deadlock between get_online_cpus/pcpu_alloc
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On Tue, 7 Feb 2017, Thomas Gleixner wrote:

> > Yep. Hotplug events are pretty significant. Using stop_machine_XXXX() etc
> > would be advisable and that would avoid the taking of locks and get rid of all the
> > ocmplexity, reduce the code size and make the overall system much more
> > reliable.
>
> Huch? stop_machine() is horrible and heavy weight. Don't go there, there
> must be simpler solutions than that.

Inserting or removing hardware is a heavy process. This would help quite a
bit with these issues for loops over active cpus.