linux-kernel - Re: [PATCH] workqueue: remove the empty check in too_many

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Date:	Thu, 19 Jun 2014 12:25:13 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Lai Jiangshan <laijs@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] workqueue: remove the empty check in too_many_workers()

On Tue, Jun 03, 2014 at 03:32:07PM +0800, Lai Jiangshan wrote:
> The commit ea1abd6197d5 ("workqueue: reimplement idle worker rebinding")
> used a trick which simply removes all to-be-bound idle workers from the
> idle list and lets them add themselves back after completing rebinding.
> 
> And this trick caused the @worker_pool->nr_idle may deviate than the actual
> number of idle workers on @worker_pool->idle_list.  More specifically,
> nr_idle may be non-zero while ->idle_list is empty.  All users of
> ->nr_idle and ->idle_list are audited.  The only affected one is
> too_many_workers() which is updated to check %false if ->idle_list is
> empty regardless of ->nr_idle.
> 
> The commit/trick was complicated due to it just tried to simplify an even
> more complicated problem (workers had to rebind itself). But the commit
> a9ab775bcadf ("workqueue: directly restore CPU affinity of workers
> from CPU_ONLINE") fixed all these problems and the mentioned trick was
> useless and is gone.
> 
> So, now the @worker_pool->nr_idle is exactly the actual number of workers
> on @worker_pool->idle_list. too_many_workers() should recover as it was
> before the trick. So we remove the empty check.
> 
> Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>

Applied to wq/for-3.17.

Thanks.

-- 
tejun
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