Date: Sun, 13 Jun 2010 17:53:54 +0200
From: Oleg Nesterov <oleg@redhat.com>
To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Roland McGrath <roland@redhat.com>, LKML <linux-kernel@vger.kernel.org>,
       linux-mm <linux-mm@kvack.org>, David Rientjes <rientjes@google.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
       Nick Piggin <npiggin@suse.de>
Subject: Re: [PATCH] oom: Make coredump interruptible
Message-ID: <20100613155354.GA8428@redhat.com>
References: <20100604112721.GA12582@redhat.com> <20100609195309.GA6899@redhat.com> <20100613175547.616F.A69D9226@jp.fujitsu.com>
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On 06/13, KOSAKI Motohiro wrote:
>
> > On 06/04, Oleg Nesterov wrote:
> > >
> > Perhaps something like below makes sense for now.
>
> Probably, this works. at least I don't find any problems.
> But umm... Do you mean we can't implement per-process oom flags?

Sorry, can't understand what you mean.

> example,
> 	1) back to implement signal->oom_victim
> 	   because We are using SIGKILL for OOM and struct signal
> 	   naturally represent signal target.

Yes, but if this process participates in the coredump, we should find
the right thread, or mark mm or mm->core_state.

In fact, I was never sure that oom-kill should kill the single process.
Perhaps it should kill all tasks using the same ->mm instead. But this
is another story.

> 	2) mm->nr_oom_killed_task
> 	   just avoid simple flag. instead counting number of tasks of
> 	   oom-killed.

again, can't understand.

> I think both avoid your explained problem. Am I missing something?

I guess that I am missing something ;) Please clarify?

> But, again, I have no objection to your patch. because I really hope to
> fix coredump vs oom issue.

Yes, I think this is important. And if we keep the PF_EXITING check in
select_bad_process(), it should be fixed so that at least the coredump
can't fool it. And the "p != current" is obviously not right too.

I'll try to do something next week, the patches should be simple.

Oleg.

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