Re: [linux-3.14 bisection] complete test-amd64-i386-xl-qcow2

[Ian Campbell <ian.campbell@citrix.com>]

On Tue, 2015-09-01 at 10:57 +0100, Ian Jackson wrote:
> Ian Campbell writes ("Re: [linux-3.14 bisection] complete test-amd64-i386
> -xl-qcow2"):
> > On Wed, 2015-08-26 at 20:02 +0000, osstest service owner wrote:
> > >   commit 9e6c072a69d87100808d16279d60e9f857291340
> > >   Author: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com
> > > >
> > >   Date:   Fri Jun 26 03:28:24 2015 +0200
> > >   
> > >       xen/gntdevt: Fix race condition in gntdev_release()
> > 
> > I'm not sure what to make of this.
> > 
> > The qcow2 test is one of the only ones I'd expect to be exercising 
> > gntdev
> > (most tests use LVM+blkback), which explains why this particular commit 
> > is
> > apparently seeing issues due to this particular change.
> 
> (You mean `which explains why this particular _test_ is [failing]',
> I think.)

Indeed.

> The host serial log in one of the confirmation tests of 9e6c072a shows
> serious trouble:
> 
>  http://logs.test-lab.xenproject.org/osstest/logs/60893/test-amd64-i386
> -xl-qcow2/serial-huxelrebe1.log
> 
>  Aug 26 19:36:51.841068 [  738.050547] BUG: unable to handle kernel
>  NULL pointer dereference at 00000014
> 
>  Aug 26 19:36:56.753068 [  738.050594] IP: [<c11829d3>]
>  __mmu_notifier_invalidate_range_start+0x33/0x70
> 
> And the immediately preceding confirmation flight, which got a pass on
> 9e6c072a~1, seems fine:
> 
>  http://logs.test-lab.xenproject.org/osstest/logs/60892/test-amd64-i386
> -xl-qcow2/serial-huxelrebe1.log
> 
> But, it's difficult to see how that gntdev fix would be responsible
> for the bug.  Perhaps it changes the order in which certain things
> happen so as to expose another bug.

Or perhaps there was a fix and/or change in behaviour in the mmunotifier
stuff which the patch relied on but which isn't in 3.14?

Ian.

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