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

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Message-ID: <20071016062108.GB1000@ff.dom.local>
Date:	Tue, 16 Oct 2007 08:21:08 +0200
From:	Jarek Poplawski <jarkao2@...pl>
To:	"Maciej W\. Rozycki" <macro@...ux-mips.org>
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, Oct 15, 2007 at 06:03:20PM +0100, Maciej W. Rozycki wrote:
> 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
> 

Yes, it's all right here. Sorry for bothering - I should've found this
by myself.

I've still some doubts about this possible enable_irq() after
free_irq(). If it's the only handler the status would be changed again
and at least some of this code in check_irq_resend() would be run, but
I can miss something again or/and this doesn't matter, as well.

Thanks,
Jarek P.
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