linux-kernel - Re: 2.6.21-rc7-mm2 "irqpoll" seems to be broken

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Message-ID: <20070517215654.GA31149@suse.de>
Date:	Thu, 17 May 2007 23:56:54 +0200
From:	Bernhard Walle <bwalle@...e.de>
To:	Vivek Goyal <vgoyal@...ibm.com>
Cc:	Morton Andrew Morton <akpm@...ux-foundation.org>,
	linux kernel mailing list <linux-kernel@...r.kernel.org>
Subject: Re: 2.6.21-rc7-mm2 "irqpoll" seems to be broken

* Vivek Goyal <vgoyal@...ibm.com> [2007-05-17 15:05]:
> On Mon, May 14, 2007 at 04:05:15PM +0200, Bernhard Walle wrote:
> > * Vivek Goyal <vgoyal@...ibm.com> [2007-05-08 19:18]:
> > > On Thu, May 03, 2007 at 12:19:32AM +0200, Bernhard Walle wrote:
> > > > * Vivek Goyal <vgoyal@...ibm.com> [2007-04-30 10:48]:
> > > > > 
> > > > > handle_edge_irq() already makes sure that desc->action is not null, still
> > > > > note_interrupt() is receiving desc->action as null, that's strange. On my 
> > > > > system this is happening for irq 4 and /proc/interrupt shows that it is
> > > > > coming from "serial".
> > > > 
> > > > Unfortunately, I couldn't reproduce this here. Vivek, do you have time
> > > > to take a look at this at your site? For the meanwhile, should I
> > > > create a patch that checks for desc->action in note_interrupt(), too?
> > > 
> > > I can reproduce this problem only on one machine. I think there is some
> > > race condition and your code somehow just exposes it.
> > 
> > thanks for finding that out. Could you try/review out the patch below?
> > As the lock is only aquired when irqfixup == 2 it shouldn't impact
> > performance of a 'normal' system.
> 
> It does fix up my problem. I have modified your patch a bit. I think
> new version is little more clear. What do you think?

Aggreed. Thanks for spotting that problem out!


Bernhard
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