linux-kernel - Re: [PATCH -mm v2 1/3] mm/oom_kill: remove the wrong fatal_signal_pending() check in oom_kill

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Date:	Thu, 1 Oct 2015 19:53:19 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Michal Hocko <mhocko@...nel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Kyle Walker <kwalker@...hat.com>,
	Stanislav Kozina <skozina@...hat.com>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH -mm v2 1/3] mm/oom_kill: remove the wrong
	fatal_signal_pending() check in oom_kill_process()

On 10/01, Michal Hocko wrote:
>
> zap_process will add SIGKILL to all threads but the
> current which will go on without being killed and if this is not a
> thread group leader then we would miss it.

Yes. And note that de_thread() does the same. Speaking of oom-killer
this is mostly fine, the execing thread is going to release its old
->mm and it has already passed the copy_strings() stage which can use
a lot more memory.

But in theory (in practice currently this seems impossible without
SIGKILL) exec can fail before exec_mmap(), so if we want to zap its
->mm we need to ensure it can't return to user space.

> Acked-by: Michal Hocko <mhocko@...e.com>

Thanks!

Oleg.

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