kernel BUG at drivers/xen/grant-table.c:923!

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

(Was Re: [osstest test] 50423: regressions - FAIL)

This cropped up in an osstest flight (the results only go to Ian and I).

On Fri, 2015-04-17 at 11:10 +0100, Ian Campbell wrote:
> On Thu, 2015-04-16 at 21:36 +0000, osstest service user wrote:
> > flight 50423 osstest real [real]
> > http://logs.test-lab.xenproject.org/osstest/logs/50423/
> > 
> > Regressions :-(
> > 
> > Tests which did not succeed and are blocking,
> > including tests which could not be run:
> >  test-armhf-armhf-xl          15 guest-start/debian.repeat fail REGR. vs. 50331
> 
> 
> Looks to have been a real issue:
> 
> http://logs.test-lab.xenproject.org/osstest/logs/50423/test-armhf-armhf-xl/serial-cubietruck-gleizes.log
> Apr 14 19:01:21.834851 [ 1229.470934] ------------[ cut here ]------------
> Apr 14 19:01:22.445308 [ 1229.471001] kernel BUG at drivers/xen/grant-table.c:923!

This seems familiar, anyone remember it? (CCing ARM, netback and generic
Linux maintainers).

I had a look over

$ git log v3.16..origin/master -- drivers/net/xen-netback/ drivers/xen/ arch/*/xen

and nothing jumped out at me.

The new tests under flight include running tcpdump for the duration of
the migration. I wonder if that might have exposed the problem?

This is ARM for which osstest uses a 3.16 based kernel compared with x86
which is still on 3.14. That might explain why this was only seen on arm
(if tcpdump triggered it) or it might just be a very rare occurrence.

> Apr 14 19:01:22.450646 [ 1229.471026] Internal error: Oops - BUG: 0 [#1] SMP ARM
> Apr 14 19:01:22.455886 [ 1229.471052] Modules linked in: xen_gntalloc bridge stp ipv6 llc brcmfmac brcmutil cfg80211
> Apr 14 19:01:22.464140 [ 1229.471145] CPU: 0 PID: 18258 Comm: vif9.0-q0-guest Not tainted 3.16.7-ckt4+ #1
> Apr 14 19:01:22.471529 [ 1229.471181] task: d80e0d80 ti: db730000 task.ti: db730000
> Apr 14 19:01:22.477016 [ 1229.471219] PC is at gnttab_batch_copy+0xd4/0xe0
> Apr 14 19:01:22.481638 [ 1229.471257] LR is at gnttab_batch_copy+0x1c/0xe0
> Apr 14 19:01:22.486422 [ 1229.471285] pc : [<c04ab434>]    lr : [<c04ab37c>]    psr: a0000013
> Apr 14 19:01:22.492642 [ 1229.471285] sp : db731eb0  ip : deadbeef  fp : db731f3c
> Apr 14 19:01:22.498021 [ 1229.471329] r10: 00000001  r9 : 00000000  r8 : 00000002
> Apr 14 19:01:22.503293 [ 1229.471352] r7 : 00000001  r6 : 00000001  r5 : 00000000  r4 : e2003d30
> Apr 14 19:01:22.509907 [ 1229.471380] r3 : 00000001  r2 : deadbeef  r1 : deadbeef  r0 : fffffff2
> Apr 14 19:01:22.516431 [ 1229.471409] Flags: NzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment kernel
> Apr 14 19:01:22.523802 [ 1229.471440] Control: 10c5387d  Table: 7987806a  DAC: 00000015
> Apr 14 19:01:22.529651 [ 1229.471469] Process vif9.0-q0-guest (pid: 18258, stack limit = 0xdb730248)
> Apr 14 19:01:22.536553 [ 1229.471515] Stack: (0xdb731eb0 to 0xdb732000)
> Apr 14 19:01:22.541024 [ 1229.471543] 1ea0:                                     00000001 00000000 00000000 e1ffb000
> Apr 14 19:01:22.549146 [ 1229.471581] 1ec0: 00000001 c05d6acc 0000004e 00000a02 db731f3c 00000000 00000000 00000001
> Apr 14 19:01:22.557387 [ 1229.471626] 1ee0: dbbbfcc0 00000000 00000000 00000002 00000000 db731f20 e2003cfc e2003d30
> Apr 14 19:01:22.565641 [ 1229.471663] 1f00: 00000001 00000000 00000001 00000000 e2003d30 e202e530 0000004e 00000202
> Apr 14 19:01:22.573891 [ 1229.471699] 1f20: d290ee40 d290ee40 00000001 00000000 db731f2c db731f34 db731f34 00000000
> Apr 14 19:01:22.582139 [ 1229.471736] 1f40: 00000000 db56d240 00000000 e1ffb000 c05d65f4 00000000 00000000 00000000
> Apr 14 19:01:22.590388 [ 1229.471772] 1f60: 00000000 c0264048 00000000 00000000 00000000 e1ffb000 00000000 00000000
> Apr 14 19:01:22.598639 [ 1229.471808] 1f80: db731f80 db731f80 00000000 00000000 db731f90 db731f90 db731fac db56d240
> Apr 14 19:01:22.606888 [ 1229.471843] 1fa0: c0263f7c 00000000 00000000 c020f038 00000000 00000000 00000000 00000000
> Apr 14 19:01:22.615016 [ 1229.471879] 1fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> Apr 14 19:01:22.623268 [ 1229.471914] 1fe0: 00000000 00000000 00000000 00000000 00000013 00000000 00000000 00000000
> Apr 14 19:01:22.631514 [ 1229.471978] [<c04ab434>] (gnttab_batch_copy) from [<c05d6acc>] (xenvif_kthread_guest_rx+0x4d8/0xbc0)
> Apr 14 19:01:22.640766 [ 1229.472045] [<c05d6acc>] (xenvif_kthread_guest_rx) from [<c0264048>] (kthread+0xcc/0xe8)
> Apr 14 19:01:22.648924 [ 1229.472093] [<c0264048>] (kthread) from [<c020f038>] (ret_from_fork+0x14/0x3c)
> Apr 14 19:01:22.656138 [ 1229.472132] Code: 0affffe5 eaffffed e8bd80f8 e7f001f2 (e7f001f2) 
> Apr 14 19:01:22.662285 [ 1229.472180] ---[ end trace 47a1647ddcea66dd ]---