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From: Shayan Pooya <shayan@liveve.org>
Date: Fri, 15 Jul 2016 09:58:58 -0700
Message-ID: <CABAubTjjD6nmAtMNze5O6-bE-ivMmb24Jd4u2mMpBZFBFR1CnA@mail.gmail.com>
Subject: Re: bug in memcg oom-killer results in a hung syscall in another
 process in the same cgroup
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Sender: owner-linux-mm@kvack.org
List-ID: <linux-mm.kvack.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>, Michal Hocko <mhocko@kernel.org>, Konstantin Khlebnikov <koct9i@gmail.com>, cgroups mailinglist <cgroups@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>, linux-mm@kvack.org

>> I am just curious... can you reproduce the problem reliably? If yes, can you try
>> the patch below ? Just in case, this is not the real fix in any case...
>
> Yes. It deterministically results in hung processes in vanilla kernel.
> I'll try this patch.

I'll have to correct this. I can reproduce this issue easily on
high-end servers and normal laptops. But for some reason it does not
happen very often in vmware guests (maybe related to lower
parallelism).

>> --- x/kernel/sched/core.c
>> +++ x/kernel/sched/core.c
>> @@ -2793,8 +2793,11 @@ asmlinkage __visible void schedule_tail(struct task_struct *prev)
>>         balance_callback(rq);
>>         preempt_enable();
>>
>> -       if (current->set_child_tid)
>> +       if (current->set_child_tid) {
>> +               mem_cgroup_oom_enable();
>>                 put_user(task_pid_vnr(current), current->set_child_tid);
>> +               mem_cgroup_oom_disable();
>> +       }
>>  }
>>
>>  /*

I tried this patch and I still see the same stuck processes (assuming
that's what you were curious about).

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