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

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Message-Id: <200706240154.53351.rjw@sisk.pl>
Date:	Sun, 24 Jun 2007 01:54:52 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	"Siddha, Suresh B" <suresh.b.siddha@...el.com>
Cc:	"Darrick J. Wong" <djwong@...ibm.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org, ak@...e.de
Subject: Re: Device hang when offlining a CPU due to IRQ misrouting

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.

Greetings,
Rafael


-- 
"Premature optimization is the root of all evil." - Donald Knuth
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