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

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

ping for 3.10.y and 3.14.y

Thanks,
Ian.

On Wed, 2015-09-02 at 10:18 +0100, Ian Campbell wrote:
> [resending to correct stable address, sorry folks]
> 
> TL;DR: Any backport of 30b03d05e074 to earlier than commit 1401c00e59e
> ("xen/gntdev: convert priv->lock to a mutex", which was added in v4.0)
> needs $something doing to it, either s/mutex/spinlock/ or (more likely)
> backporting of 1401c00e59e too.
> 
> Looking at LTS:
> 
> 3.18.y:	  Backported both.
> 3.16.y:	  Has backported neither
> 3.14.y:	* Only backported 30b03d05e074
> 3.12.y:	  Has backported neither
> 3.10.y:	* Only backported 30b03d05e074
> 3.4.y:	  Has backported neither
> 3.2.y:	  Has backported neither
> 
> So AFAICT 3.14.y and 3.10.y need fixes, probably following 3.18 and
> backporting 1401c00e59e.
> 
> 3.16/12/4/2 might need to be careful if they subsequently pick up
> 30b03d05.
> 
> See below for the build log error.
> 
> On Tue, 2015-09-01 at 11:05 +0100, Ian Campbell wrote:
> > 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-i3
> > > 86
> > > -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: []
> > >  __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-i3
> > > 86
> > > -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?
> 
> Looking at http://logs.test-lab.xenproject.org/osstest/logs/60949/'s buil
> d
> jobs:
> http://logs.test-lab.xenproject.org/osstest/logs/60949/build-amd64
> -pvops/5.ts-kernel-build.log contains:
> 
> drivers/xen/gntdev.c: In function ‘gntdev_release’:
> drivers/xen/gntdev.c:532:2: warning: passing argument 1 of
> ‘mutex_lock’
> from incompatible pointer type [enabled by default]
> In file included from include/linux/notifier.h:13:0,
>                  from include/linux/memory_hotplug.h:6,
>                  from include/linux/mmzone.h:821,
>                  from include/linux/gfp.h:5,
>                  from include/linux/kmod.h:22,
>                  from include/linux/module.h:13,
>                  from drivers/xen/gntdev.c:24:
> include/linux/mutex.h:157:13: note: expected ‘struct mutex *’ but
> argument is of type ‘struct spinlock_t *’
> drivers/xen/gntdev.c:539:2: warning: passing argument 1 of
> ‘mutex_unlock’ from incompatible pointer type [enabled by default]
> In file included from include/linux/notifier.h:13:0,
>                  from include/linux/memory_hotplug.h:6,
>                  from include/linux/mmzone.h:821,
>                  from include/linux/gfp.h:5,
>                  from include/linux/kmod.h:22,
>                  from include/linux/module.h:13,
>                  from drivers/xen/gntdev.c:24:
> include/linux/mutex.h:174:13: note: expected ‘struct mutex *’ but
> argument is of type ‘struct spinlock_t *’
> 
> Which is somehow a warning and not a build failure.
> 
> Ian.