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[Xen-devel] Re: [PATCH] blkfront: Move blkif_interrupt into a tasklet.

To: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Subject: [Xen-devel] Re: [PATCH] blkfront: Move blkif_interrupt into a tasklet.
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Thu, 23 Sep 2010 11:36:13 -0700
Cc: Andrew Jones <drjones@xxxxxxxxxx>, Xen <xen-devel@xxxxxxxxxxxxxxxxxxx>, Tom Kopec <tek@xxxxxxx>, Daniel Stodden <daniel.stodden@xxxxxxxxxx>
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 On 09/23/2010 09:38 AM, Paolo Bonzini wrote:
> On 09/23/2010 06:23 PM, Jeremy Fitzhardinge wrote:
>>> Any developments with this? I've got a report of the exact same
>>> warnings
>>> on RHEL6 guest. See
>>> https://bugzilla.redhat.com/show_bug.cgi?id=632802
>>> RHEL6 doesn't have the 'Move blkif_interrupt into a tasklet' patch, so
>>> that can be ruled out. Unfortunately I don't have this reproducing on a
>>> test machine, so it's difficult to debug.  The report I have showed
>>> that
>>> in at least one case it occurred on boot up, right after initting the
>>> block device. I'm trying to get confirmation if that's always the case.
>>> Thanks in advance for any pointers you might have.
>> Yes, I see it even after reverting that change as well.  However I only
>> see it on my domain with an XFS filesystem, but I haven't dug any deeper
>> to see if that's relevant.
>> Do you know when this appeared?  Is it recent?  What changes are in the
>> rhel6 kernel in question?
> It's got pretty much everything in stable-2.6.32.x, up to the 16 patch
> blkfront series you posted last July.  There are some RHEL-specific
> workarounds for PV-on-HVM, but for PV domains everything matches
> upstream.

Have you tried bisecting to see when this particular problem appeared? 
It looks to me like something is accidentally re-enabling interrupts -
perhaps a stack overrun is corrupting the "flags" argument between a
spin_lock_irqsave()/restore pair. 

Is it only on 32-bit kernels?


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