Re: [PATCH 04/40] sched: implement __set_cpus_allowed()

From: Peter Zijlstra
Date: Tue Jan 19 2010 - 03:37:55 EST

On Tue, 2010-01-19 at 10:07 +0900, Tejun Heo wrote:
> It's also necessary to guarantee forward progress during CPU_DOWN.
> The problem with kthread_bind() is that it's not synchronized against
> CPU hotplug operations. It needs outer synchronization like calling
> it directly from CPU_DOWN_PREP. I guess it's doable but I think it
> would be better to simply share the backend implementation between
> set_cpus_allowed_ptr() and kthread_bind().

OK, so you're saying you need to migrate the rescue thread during
cpu-down. That thread is guaranteed sleeping right, if it were not it'd
not be elegible to run on our dying cpu. Hence kthread_bind() ought to
just work, no?

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