Re: a non producible kernel panic

[Alex,Shi]

On Sun, 2012-02-05 at 12:28 +0800, Alex Shi wrote:
> When do performance testing for rc2 kernel on our NHM EX machine( 4
> sockets * 8 cores), I find a kernel panic. but never reproduced it. and
> didn't find some useful info after enable lockdep, rcu debug etc.

BTW, the panic caused my machine hang. 
> 
> Any ideas on this?
> 
> INFO: task umount:4280 blocked for more than 120 seconds.
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> umount          D ffff883025443198     0  4280   4235 0x00000080
>  ffff883027805d28 0000000000000086 ffff883025442de0 ffff883027805fd8
>  ffff883027805fd8 0000000000013100 ffff8810292eade0 ffff883025442de0
>  0000000000000018 7fffffffffffffff 7fffffffffffffff ffffffff81c180c8
> Call Trace:
>  [<ffffffff81452caa>] schedule+0x55/0x57
>  [<ffffffff81451a93>] schedule_timeout+0x2f/0xd9
>  [<ffffffff8109dfe0>] ? rcu_panic+0x12/0x12
>  [<ffffffff81028259>] ? physflat_send_IPI_allbutself+0x12/0x14
>  [<ffffffff81024a33>] ? native_send_call_func_ipi+0x71/0x91
>  [<ffffffff81452b67>] wait_for_common+0x95/0xeb
>  [<ffffffff8105dfe7>] ? try_to_wake_up+0x1e0/0x1e0
>  [<ffffffff8109dfe0>] ? rcu_panic+0x12/0x12
>  [<ffffffff8109eb41>] ? call_rcu_bh+0x12/0x12
>  [<ffffffff81452c53>] wait_for_completion+0x18/0x1a
>  [<ffffffff8109ef36>] _rcu_barrier+0x96/0xa6
>  [<ffffffff8109ef5d>] rcu_barrier_sched+0x17/0x19
>  [<ffffffff8109ef68>] rcu_barrier+0x9/0xb
>  [<ffffffff8110bac0>] deactivate_locked_super+0x32/0x52
>  [<ffffffff8110c536>] deactivate_super+0x32/0x36
>  [<ffffffff81120691>] mntput_no_expire+0xde/0xe7
>  [<ffffffff811212f2>] sys_umount+0x2cd/0x2ff
>  [<ffffffff81112699>] ? path_put+0x1a/0x1e
>  [<ffffffff81459a79>] system_call_fastpath+0x16/0x1b
> INFO: task umount:4280 blocked for more than 120 seconds.
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> umount          D ffff883025443198     0  4280   4235 0x00000080
>  ffff883027805d28 0000000000000086 ffff883025442de0 ffff883027805fd8
>  ffff883027805fd8 0000000000013100 ffff8810292eade0 ffff883025442de0
>  0000000000000018 7fffffffffffffff 7fffffffffffffff ffffffff81c18


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