linux-kernel - Re: [PATCH 8/8] mm: Give up allocation if the task have fatal signal

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Date:	Tue, 15 Dec 2009 10:03:42 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	Minchan Kim <minchan.kim@...il.com>,
	Rik van Riel <riel@...hat.com>, lwoodman@...hat.com,
	akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 8/8] mm: Give up allocation if the task have fatal
 signal

On Tue, 15 Dec 2009 09:50:47 +0900 (JST)
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> wrote:

> > >  	/*
> > > +	 * If the allocation is for userland page and we have fatal signal,
> > > +	 * there isn't any reason to continue allocation. instead, the task
> > > +	 * should exit soon.
> > > +	 */
> > > +	if (fatal_signal_pending(current) && (gfp_mask & __GFP_HIGHMEM))
> > > +		goto nopage;
> > 
> > If we jump nopage, we meets dump_stack and show_mem. 
> > Even, we can meet OOM which might kill innocent process.
> 
> Which point you oppose? noprint is better?
> 
> 

Sorry fot not clarity.
My point was following as. 

First,
I don't want to print.
Why do we print stack and mem when the process receives the SIGKILL?

Second, 
1) A process try to allocate anon page in do_anonymous_page.
2) A process receives SIGKILL.
3) kernel doesn't allocate page to A process by your patch.
4) do_anonymous_page returns VF_FAULT_OOM.
5) call mm_fault_error
6) call out_of_memory 
7) It migth kill innocent task. 

If I missed something, Pz, corret me. :)

-- 
Kind regards,
Minchan Kim
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