linux-kernel - Re: Device hang when offlining a CPU due to IRQ misrouting

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Date:	Sat, 23 Jun 2007 16:58:41 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	"Siddha, Suresh B" <suresh.b.siddha@...el.com>,
	"Darrick J. Wong" <djwong@...ibm.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org, ak@...e.de
Subject: Re: Device hang when offlining a CPU due to IRQ misrouting

On Sun, 24 Jun 2007 01:54:52 +0200 "Rafael J. Wysocki" <rjw@...k.pl> wrote:

> On Wednesday, 20 June 2007 00:08, Siddha, Suresh B wrote:
> > On Tue, Jun 19, 2007 at 01:49:30PM -0700, Darrick J. Wong wrote:
> > > 
> > > This fixes the problem!  Hurrah!
> > 
> > Great!  Andrew, please include the appended patch in -mm.
> > 
> > ----
> > Subject: [patch] x86_64, irq: use mask/unmask and proper locking in fixup_irqs
> > From: Suresh Siddha <suresh.b.siddha@...el.com>
> > 
> > Force irq migration path during cpu offline, is not using proper
> > locks and irq_chip mask/unmask routines. This will result in
> > some races(especially the device generating the interrupt can see
> > some inconsistent state, resulting in issues like stuck irq,..).
> > 
> > Appended patch fixes the issue by taking proper lock and
> > encapsulating irq_chip set_affinity() with a mask() before and an
> > unmask() after.
> > 
> > This fixes a MSI irq stuck issue reported by Darrick Wong.
> > 
> > There are several more general bugs in this area(irq migration in the
> > process context). For example,
> > 
> > 1. Possibility of missing edge triggered irq.
> > 2. Reliable method of migrating level triggered irq in the process context.
> > 
> > We plan to look and close these in the near future.
> 
> This patch breaks hibernation on my Turion 64 X2 - based testbox (HPC nx6325).
> 
> _cpu_down() just hangs as though there were a deadlock in there, 100% of the
> time.
> 

Thanks, I dropped it.
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