Re: process hangs on do_exit when oom happens

From: Qiang Gao
Date: Tue Oct 23 2012 - 03:18:40 EST

This process was moved to RT-priority queue when global oom-killer
happened to boost the recovery
of the system.. but it wasn't get properily dealt with. I still have
no idea why where the problem is ..
On Tue, Oct 23, 2012 at 12:40 PM, Balbir Singh <bsingharora@xxxxxxxxx> wrote:
> On Tue, Oct 23, 2012 at 9:05 AM, Qiang Gao <gaoqiangscut@xxxxxxxxx> wrote:
>> information about the system is in the attach file "information.txt"
>>
>> I can not reproduce it in the upstream 3.6.0 kernel..
>>
>> On Sat, Oct 20, 2012 at 12:04 AM, Michal Hocko <mhocko@xxxxxxx> wrote:
>>> On Wed 17-10-12 18:23:34, gaoqiang wrote:
>>>> I looked up nothing useful with google,so I'm here for help..
>>>>
>>>> when this happens: I use memcg to limit the memory use of a
>>>> process,and when the memcg cgroup was out of memory,
>>>> the process was oom-killed however,it cannot really complete the
>>>> exiting. here is the some information
>>>
>>> How many tasks are in the group and what kind of memory do they use?
>>> Is it possible that you were hit by the same issue as described in
>>> 79dfdacc memcg: make oom_lock 0 and 1 based rather than counter.
>>>
>>>> OS version: centos6.2 2.6.32.220.7.1
>>>
>>> Your kernel is quite old and you should be probably asking your
>>> distribution to help you out. There were many fixes since 2.6.32.
>>> Are you able to reproduce the same issue with the current vanila kernel?
>>>
>>>> /proc/pid/stack
>>>> ---------------------------------------------------------------
>>>>
>>>> [<ffffffff810597ca>] __cond_resched+0x2a/0x40
>>>> [<ffffffff81121569>] unmap_vmas+0xb49/0xb70
>>>> [<ffffffff8112822e>] exit_mmap+0x7e/0x140
>>>> [<ffffffff8105b078>] mmput+0x58/0x110
>>>> [<ffffffff81061aad>] exit_mm+0x11d/0x160
>>>> [<ffffffff81061c9d>] do_exit+0x1ad/0x860
>>>> [<ffffffff81062391>] do_group_exit+0x41/0xb0
>>>> [<ffffffff81077cd8>] get_signal_to_deliver+0x1e8/0x430
>>>> [<ffffffff8100a4c4>] do_notify_resume+0xf4/0x8b0
>>>> [<ffffffff8100b281>] int_signal+0x12/0x17
>>>> [<ffffffffffffffff>] 0xffffffffffffffff
>>>
>>> This looks strange because this is just an exit part which shouldn't
>>> deadlock or anything. Is this stack stable? Have you tried to take check
>>> it more times?
>
> Looking at information.txt, I found something interesting
>
> rt_rq[0]:/1314
> .rt_nr_running : 1
> .rt_throttled : 1
> .rt_time : 0.856656
> .rt_runtime : 0.000000
>
>
> cfs_rq[0]:/1314
> .exec_clock : 8738.133429
> .MIN_vruntime : 0.000001
> .min_vruntime : 8739.371271
> .max_vruntime : 0.000001
> .spread : 0.000000
> .spread0 : -9792.255554
> .nr_spread_over : 1
> .nr_running : 0
> .load : 0
> .load_avg : 7376.722880
> .load_period : 7.203830
> .load_contrib : 1023
> .load_tg : 1023
> .se->exec_start : 282004.715064
> .se->vruntime : 18435.664560
> .se->sum_exec_runtime : 8738.133429
> .se->wait_start : 0.000000
> .se->sleep_start : 0.000000
> .se->block_start : 0.000000
> .se->sleep_max : 0.000000
> .se->block_max : 0.000000
> .se->exec_max : 77.977054
> .se->slice_max : 0.000000
> .se->wait_max : 2.664779
> .se->wait_sum : 29.970575
> .se->wait_count : 102
> .se->load.weight : 2
>
> So 1314 is a real time process and
>
> cpu.rt_period_us:
> 1000000
> ----------------------
> cpu.rt_runtime_us:
> 0
>
> When did tt move to being a Real Time process (hint: see nr_running
> and nr_throttled)?
>
> Balbir
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