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

[Daniel Stodden <daniel.stodden@xxxxxxxxxx>]

On Mon, 2010-09-27 at 03:41 -0400, Andrew Jones wrote:
> On 09/24/2010 08:50 PM, Jeremy Fitzhardinge wrote:
> >  On 09/24/2010 12:14 AM, Andrew Jones wrote:
> >> On 09/23/2010 08:36 PM, Jeremy Fitzhardinge wrote:
> >>>  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. 
> >>>
> >> Unfortunately I don't have a test machine where I can do a bisection
> >> (yet). I'm looking for one. I only have this one report so far, and it's
> >> on a production machine.
> > 
> > The report says that its repeatedly killing the machine though?  In my
> > testing, it seems to hit the warning once at boot, but is OK after that
> > (not that I'm doing anything very stressful on the domain).
> > 
> 
> It looks like the crash is from failing to read swap due to a bad page
> map. It's possibly another issue, but I wanted to try and clean this
> issue up first to see what happens.

Uh oh. Sure this was a frontend crash? If you see it a again, a stack
trace to look at would be great.

Thanks,
Daniel





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