linux-kernel - Re: [PATCH 12/12] oom: give current access to memory reserves if it has been killed

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Date:	Tue, 8 Jun 2010 11:26:48 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
cc:	"Luis Claudio R. Goncalves" <lclaudio@...g.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>, Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Nick Piggin <npiggin@...e.de>
Subject: Re: [PATCH 12/12] oom: give current access to memory reserves if it
 has been killed

On Tue, 8 Jun 2010, KOSAKI Motohiro wrote:

> > diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> > index 67b5fa5..ad85e1b 100644
> > --- a/mm/oom_kill.c
> > +++ b/mm/oom_kill.c
> > @@ -638,6 +638,16 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
> >  	}
> >  
> >  	/*
> > +	 * If current has a pending SIGKILL, then automatically select it.  The
> > +	 * goal is to allow it to allocate so that it may quickly exit and free
> > +	 * its memory.
> > +	 */
> > +	if (fatal_signal_pending(current)) {
> > +		set_tsk_thread_flag(current, TIF_MEMDIE);
> > +		return;
> > +	}
> 
> Self NAK this.
> We have no gurantee that current is oom killable. Oh, here is
> out_of_memory(), sigh.
> 

We're not killing it, it's already dying.  We're simply giving it access 
to memory reserves so it may allocate and quickly exit to free its memory.  
Being OOM_DISABLE does not imply the task cannot exit or use memory 
reserves in the exit path.
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