linux-kernel - Re: [PATCH 11/25] pm: don't use [delayed_]work

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Message-ID: <20121225164433.GG10220@mtj.dyndns.org>
Date:	Tue, 25 Dec 2012 08:44:33 -0800
From:	Tejun Heo <tj@...nel.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH 11/25] pm: don't use [delayed_]work_pending()

Hello, Rafael.

On Sat, Dec 22, 2012 at 12:53:29PM +0100, Rafael J. Wysocki wrote:
> On Friday, December 21, 2012 05:57:01 PM Tejun Heo wrote:
> > There's no need to test whether a (delayed) work item in pending
> > before queueing, flushing or cancelling it.  Most uses are unnecessary
> > and quite a few of them are buggy.
> 
> Can you please say why they are buggy?

Usually one of the following two reasons.

* The user gets confused and fails to handle !PENDING && currently
  executing properly.

* work_pending() doesn't have any memory barrier and the caller
  assumes work_pending() is somehow properly synchronized by itself.

Thanks.

-- 
tejun
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