linux-kernel - Re: [PATCH 03/10 V2] workqueue: async worker destruction

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Message-ID: <20140513141418.GA23710@htj.dyndns.org>
Date:	Tue, 13 May 2014 10:14:18 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Lai Jiangshan <laijs@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/10 V2] workqueue: async worker destruction

Hello,

On Tue, May 13, 2014 at 02:32:52PM +0800, Lai Jiangshan wrote:
> >> +	if (detach_completion)
> >> +		complete(detach_completion);
> >> +}
> > 
> > Are we gonna use this function from somewhere else too?
> 
> it is called from worker_thread().
> 
> I don't want to unfold it into worker_thread(), it is better
> readability when it is wrapped and it will be called in patch10
> for rescuer.

Yeah, it's shared by rescuer later, so it's fine but, again, it
probably helps to mention that it's planned to do so; otherwise, the
rationale is kinda weak and what belongs to that function is rather
arbitrary.

> >>  	/*
> >>  	 * Become the manager and destroy all workers.  Grabbing
> >> -	 * manager_arb prevents @pool's workers from blocking on
> >> -	 * manager_mutex.
> >> +	 * manager_arb ensures manage_workers() finish and enter idle.
> > 
> > I don't follow what the above comment update is trying to say.
> 
> If a pool is destroying, the worker will not call manage_workers().
> but the existing manage_workers() may be still running.
> 
> mutex_lock(&manager_arb) in put_unbound_pool() should wait this manage_workers()
> finished due to the manager-worker (non-idle-worker) can't be destroyed.

Hmmm... I think it'd be better to spell it out then.  The single
sentence is kinda cryptic especially because the two verbs in the
sentence don't have the same subject (managee_workers() can't enter
idle).

Thanks.

-- 
tejun
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