linux-kernel - Re: [PATCH 1/2 V3] workqueue: substitute POOL_FREEZING with __WQ

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Date:	Wed, 23 Apr 2014 09:37:28 +0800
From:	Lai Jiangshan <laijs@...fujitsu.com>
To:	Tejun Heo <tj@...nel.org>
CC:	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2 V3] workqueue: substitute POOL_FREEZING with __WQ_FREEZING

On 04/23/2014 04:46 AM, Tejun Heo wrote:
> Hello,
> 
> On Tue, Apr 22, 2014 at 09:47:47AM +0800, Lai Jiangshan wrote:
>> Testing workqueue_freezing requires wq_pool_mutex held.
>> Although almost-all pwq_adjust_max_active() are called with wq_pool_mutex held,
>> except workqueue_set_max_active(). But I hope pwq_adjust_max_active()
>> don't require the heavy wq_pool_mutex.
> 
> No it doesn't require wq_pool_mutex to be held.  All it requires is
> that the changed state is visible on the subsequent
> pwq_adjust_max_active() invocatino which is already trivially
> guaranteed.
> 

Good! I understood! Could you respin the patch? I'm afraid
I can't explain it well in the comments.

For me, I always prefer locks for non-performance critical path,
locks help review, I believe your comment will do so.

Thanks,
Lai
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