linux-kernel - Re: Warn people about flush_scheduled

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Message-Id: <200912142312.20163.oliver@neukum.org>
Date:	Mon, 14 Dec 2009 23:12:20 +0100
From:	Oliver Neukum <oliver@...kum.org>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Tejun Heo <tj@...nel.org>,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: Warn people about flush_scheduled_work()

Am Montag, 14. Dezember 2009 23:02:51 schrieb Alan Stern:
> 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.

True, but what use is that if you don't know your call chain and the locks
it takes.

	Regards
		Oliver
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