linux-kernel - Re: [PATCH 3/3] workqueue: remove get_online_cpus() from apply_workqueue

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Message-ID: <20141027134120.GF4436@htj.dyndns.org>
Date:	Mon, 27 Oct 2014 09:41:20 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Lai Jiangshan <laijs@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] workqueue: remove get_online_cpus() from
 apply_workqueue_attrs()

On Wed, Oct 08, 2014 at 11:53:33AM +0800, Lai Jiangshan wrote:
> There are two aims for get_online_cpus():
>   1) Protects cpumask_of_node(node). (CPUs should stay stable)
>   2) Protects the pwq-allocation and installation
> 
> But both aims are settled by other methods in previous patches:
> cpumask_of_node(node) is replaced by wq_unbound_online_cpumask, and
> the pwq-allocation and installation are changed to be protected by
> wq_pool_mutex.  Now the get_online_cpus() is no reason to exist,
> remove it!
> 
> Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>

Well, this is very marginal and we want to add comments explaining why
this is safe, but yeah I guess it's an improvement.  Can you please
add comments explaining what states are depended upon and that they
are all protected by pool mutex?

Thanks.

-- 
tejun
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