linux-kernel - Re: [PATCH 3/4] signal: oom_kill_task: use SEND_SIG_FORCED instead of force

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Date:	Mon, 13 Feb 2012 11:49:06 -0500
From:	KOSAKI Motohiro <kosaki.motohiro@...il.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Anton Vorontsov <anton.vorontsov@...aro.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] signal: oom_kill_task: use SEND_SIG_FORCED instead of force_sig()

2012/2/10 Oleg Nesterov <oleg@...hat.com>:
> Change oom_kill_task() to use do_send_sig_info(SEND_SIG_FORCED)
> instead of force_sig(SIGKILL). With the recent changes we do not
> need force_ to kill the CLONE_NEWPID tasks.
>
> And this is more correct. force_sig() can race with the exiting
> thread even if oom_kill_task() checks p->mm != NULL, while
> do_send_sig_info(group => true) kille the whole process.
>
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>
> ---
>  mm/oom_kill.c |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 2958fd8..b1e9643 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -472,11 +472,11 @@ static int oom_kill_task(struct task_struct *p)
>                        pr_err("Kill process %d (%s) sharing same memory\n",
>                                task_pid_nr(q), q->comm);
>                        task_unlock(q);
> -                       force_sig(SIGKILL, q);
> +                       do_send_sig_info(SIGKILL, SEND_SIG_FORCED, q, true);
>                }
>
>        set_tsk_thread_flag(p, TIF_MEMDIE);
> -       force_sig(SIGKILL, p);
> +       do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true);
>
>        return 0;

I don't think I clearly understand this series. But, at least, this
patch is ok to me. thanks.
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