linux-kernel - Re: [PATCH 12/31] workqueue: update synchronization rules on workqueue->pwqs

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Message-ID: <20130310123844.GE24522@htj.dyndns.org>
Date:	Sun, 10 Mar 2013 05:38:44 -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 12/31] workqueue: update synchronization rules on
 workqueue->pwqs

Hello, Lai.

On Sun, Mar 10, 2013 at 06:09:28PM +0800, Lai Jiangshan wrote:
> >  #define for_each_pwq(pwq, wq)						\
> > -	list_for_each_entry((pwq), &(wq)->pwqs, pwqs_node)
> > +	list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node)		\
> > +		if (({ assert_rcu_or_wq_lock(); true; }))
> 
> Aware this:
> 
> if (somecondition)
> 	for_each_pwq(pwq, wq)
> 		one_statement;q
> else
> 	xxxxx;
> 
> 
> for_each_pwq() will eat the else.

Yeah, but that will also generate a compiler warning.

> To avoid this, you can use:
> 
> #define for_each_pwq(pwq, wq)						\
> 	list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node)		\
> 		if (({ assert_rcu_or_wq_lock(); false; })) { }		\
> 		else
> 
> 
> The same for for_each_pool() in later patch.

Ooh, yeah, that's better.  Will do that.

Thanks.

-- 
tejun
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