linux-kernel - Re: [PATCH 14/31] workqueue: replace POOL_MANAGING_WORKERS flag with worker_pool->manager

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Date:	Sun, 10 Mar 2013 05:46:32 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Lai Jiangshan <laijs@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org, axboe@...nel.dk, jmoyer@...hat.com,
	zab@...hat.com
Subject: Re: [PATCH 14/31] workqueue: replace POOL_MANAGING_WORKERS flag with
 worker_pool->manager_mutex

Hello, Lai.

On Sun, Mar 10, 2013 at 06:09:38PM +0800, Lai Jiangshan wrote:
> > -	if (pool->flags & POOL_MANAGING_WORKERS)
> > +	if (!mutex_trylock(&pool->manager_mutex))
> >  		return ret;
> >  
> > -	pool->flags |= POOL_MANAGING_WORKERS;
> 
> 
> if mutex_trylock(&pool->manager_mutex) fails, it does not mean
> the pool is managing workers. (although current code does).
> so I recommend to keep POOL_MANAGING_WORKERS.

So, that's the intention.  It's gonna be used during pool destruction
and we want all the workers to think that the pool is being managed
and it's safe to proceed.

> I suggest that you reuse assoc_mutex for your purpose(later patches).
> (and rename assoc_mutex back to manager_mutex)

They are different.  assoc_mutex makes the workers wait for the
managership, which shouldn't happen during pool destruction.  We want
the workers to assume that the pool is managed which is what
manager_mutex achieves.

Thanks.

-- 
tejun
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