linux-kernel - Re: [PATCH 2/3] workqueue: extend wq_pool_mutex to also protect pwq-installation

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Date:	Mon, 27 Oct 2014 09:20:47 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Lai Jiangshan <laijs@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] workqueue: extend wq_pool_mutex to also protect
 pwq-installation

Hello, Lai.

On Wed, Oct 08, 2014 at 11:53:32AM +0800, Lai Jiangshan wrote:
> Athough pwq-installation without wq_pool_mutex held is not bug,
> but it is not good design, it is better to make the pwq-allocation and installation
> are in the (same) wq_pool_mutex.

WHY?  Why is that not a good design and why is extending the locking a
better thing to do?  Can you elaborate the reasoning here?

> And since the pwq-allocation and installation are in the same wq_pool_mutex,
> get_online_cpus() will not be needed for this reason, and it will be remove
> in later patch.

So, if this enables further cleanup, it's fine, but please just stick
to those reasons.  You do this a lot.  You wanna do A because of B but
the changelog often doesn't mention that at all and just goes "This is
bad so change this to be better" without any proper reasoning.  If you
want to do A to achieve B later, just say so.

Thanks.

-- 
tejun
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