linux-kernel - Re: [PATCH] workqueue: not allow recursion run

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Message-ID: <20090121105631.GD25531@elte.hu>
Date:	Wed, 21 Jan 2009 11:56:31 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Lai Jiangshan <laijs@...fujitsu.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Oleg Nesterov <oleg@...sign.ru>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] workqueue: not allow recursion run_workqueue


* Lai Jiangshan <laijs@...fujitsu.com> wrote:

> 1) lockdep will complain when recursion run_workqueue
> 2) works is not run orderly when recursion run_workqueue
> 
> 3) BUG!
>    We use recursion run_workqueue to hidden deadlock when
>    keventd trying to flush its own queue.
> 
>    It's bug. When flush_workqueue()(nested in a work callback)returns,
>    the workqueue is not really flushed, the sequence statement of
>    this work callback will do some thing bad.
> 
>    So we should not allow workqueue trying to flush its own queue.

That's a nice change. I'm wondering what the existing users are though and 
how difficult they are to fix.

	Ingo
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