linux-kernel - Re: bug in memcg oom-killer results in a hung syscall in another process in the same cgroup

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Date:	Tue, 12 Jul 2016 15:57:50 -0700
From:	Shayan Pooya <shayan@...eve.org>
To:	Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
Cc:	Michal Hocko <mhocko@...nel.org>, koct9i@...il.com,
	cgroups mailinglist <cgroups@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: bug in memcg oom-killer results in a hung syscall in another
 process in the same cgroup

> Yep. Bug still not fixed in upstream. In our kernel I've plugged it with
> this:
>
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -2808,8 +2808,9 @@ asmlinkage __visible void schedule_tail(struct
> task_struct *prev)
>         balance_callback(rq);
>         preempt_enable();
>
> -       if (current->set_child_tid)
> -               put_user(task_pid_vnr(current), current->set_child_tid);
> +       if (current->set_child_tid &&
> +           put_user(task_pid_vnr(current), current->set_child_tid))
> +               force_sig(SIGSEGV, current);
>  }

I just verified that with your patch there is no hung processes and I
see processes getting SIGSEGV as expected.
Thanks!