Re: [Xen-devel] 100% reliable Oops on xen 4.0.1

[Peter Moody <pmoody@xxxxxxxxxx>]

On Tue, Aug 14, 2012 at 7:47 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>>>> On 14.08.12 at 16:42, Peter Moody <pmoody@xxxxxxxxxx> wrote:
>> Hi Ian, here's the trace in question. I'm perfectly happy with this
>> not being a xen issue if for no other reason then it means that I have
>> one less thing I need to look at. The python script in question was
>> essentially doing the same thing as crasher.c, though in the middle of
>> other, more productive activities.
>> ...
>> Call Trace:
>>  [<ffffffff81654cd1>] ? down_read+0x11/0x30
>>  [<ffffffff811c9294>] ? ext3_xattr_get+0xf4/0x2b0
>>  [<ffffffff811baf88>] ext3_clear_blocks+0x128/0x190
>>  [<ffffffff811bb104>] ext3_free_data+0x114/0x160
>>  [<ffffffff811bbc0a>] ext3_truncate+0x87a/0x950
>>  [<ffffffff812133f5>] ? journal_start+0xb5/0x100
>>  [<ffffffff811bc840>] ext3_evict_inode+0x180/0x1a0
>>  [<ffffffff8114065f>] evict+0x1f/0xb0
>>  [<ffffffff81006d52>] ? check_events+0x12/0x20
>>  [<ffffffff81140c14>] iput+0x1a4/0x290
>>  [<ffffffff8113ed05>] dput+0x265/0x310
>>  [<ffffffff81132435>] path_put+0x15/0x30
>>  [<ffffffff810a5d31>] audit_syscall_exit+0x171/0x260
>>  [<ffffffff8103ed9a>] sysexit_audit+0x21/0x5f
>>  [<ffffffff810065ad>] ? xen_force_evtchn_callback+0xd/0x10
>>  [<ffffffff81006d52>] ? check_events+0x12/0x20
>
> This obviously is just a leftover on the stack, one can see clearly
> that we're in the middle of a syscall (which would never have
> xen_force_evtchn_callback that deep into the stack (i.e. where
> we just came from user mode).

Interesting, thanks. Do you have any idea why something like this
would only be reproducible (thus far anyway, still trying to get my
hands on some other test systems) on xen? And not just xen, but on
this particular xen configuration (huge memory, lots of cpus, etc)? Is
this likely a race condition with the audit subsystem or some other
part of the kernel that this configuration somehow tickles?

Cheers,
peter

> Jan
>



-- 
Peter Moody      Google    1.650.253.7306
Security Engineer  pgp:0xC3410038

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