linux-kernel - Re: Warn people about flush_scheduled

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Message-ID: <Pine.LNX.4.44L0.0912141701040.2690-100000@iolanthe.rowland.org>
Date:	Mon, 14 Dec 2009 17:02:51 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Oliver Neukum <oliver@...kum.org>
cc:	Tejun Heo <tj@...nel.org>,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: Warn people about flush_scheduled_work()

On Mon, 14 Dec 2009, Oliver Neukum wrote:

> Am Montag, 14. Dezember 2009 22:33:38 schrieb Alan Stern:
> >         Consider using cancel_work_sync() or cancel_delayed_work_sync()
> >         instead.  In most situations they will accomplish what you 
> >         need.
> 
> In which respect is cancel_work_sync() fundamentally safer?
> If the work is already running and takes a lock you are holding,
> then what?

With cancel_work_sync() you _know_ what locks the work item is going to
take, since it's your work item.  With flush_scheduled_work() you have
no idea what locks will be needed by the items on the queue.  They 
could come from anywhere.

Alan Stern

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