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Date: Tue, 21 Jun 2016 15:43:56 -0400
From: Tejun Heo <htejun@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Gautham R Shenoy <ego@linux.vnet.ibm.com>,
 Thomas Gleixner <tglx@linutronix.de>,
 Michael Ellerman <mpe@ellerman.id.au>,
 Abdul Haleem <abdhalee@linux.vnet.ibm.com>,
 Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>,
 linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
 kernel-team@fb.com
Subject: Re: [PATCH 1/2] workqueue: Move wq_update_unbound_numa() to the
 beginning of CPU_ONLINE
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On Tue, Jun 21, 2016 at 09:37:09PM +0200, Peter Zijlstra wrote:
> Hurm.. So I've applied it, just to get this issue sorted, but I'm not
> entirely sure I like it.
> 
> I think I prefer ego's version because that makes it harder to get stuff
> to run on !active,online cpus. I think we really want to be careful what
> gets to run during that state.

The original patch just did set_cpus_allowed one more time late enough
so that the target kthread (in most cases) doesn't have to go through
fallback rq selection afterwards.  I don't know what the long term
solution is but CPU_ONLINE callbacks should be able to bind kthreads
to the new CPU one way or the other.

Thanks.

-- 
tejun