netdev - Re: [PATCH] PHYLIB: IRQ event workqueue handling fixes

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Date:	Mon, 15 Oct 2007 18:03:20 +0100 (BST)
From:	"Maciej W. Rozycki" <macro@...ux-mips.org>
To:	Jarek Poplawski <jarkao2@...pl>
cc:	Andy Fleming <afleming@...escale.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jeff Garzik <jgarzik@...ox.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PHYLIB: IRQ event workqueue handling fixes

On Mon, 15 Oct 2007, Jarek Poplawski wrote:

> Could you explain why cancel_work_sync() is better here than
> flush_scheduled_work() wrt. rtnl_lock()?

 Well, this is actually the bit that made cancel_work_sync() be written in 
the first place.  The short story is the netlink lock is most probably 
held at this point (depending on the usage of phy_disconnect()) and there 
is also an event waiting in the queue that requires the lock, so if 
flush_scheduled_work() is called here a deadlock will happen.

 Let me find a reference for a longer story...:

http://www.linux-mips.org/cgi-bin/mesg.cgi?a=linux-mips&i=Pine.LNX.4.64N.0610031509380.4642%40blysk.ds.pg.gda.pl

and then discussed again:

http://www.uwsg.indiana.edu/hypermail/linux/kernel/0612.0/0593.html

  Maciej
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