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 10:16:53 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Minchan Kim <minchan.kim@...il.com>
Cc:	kosaki.motohiro@...fujitsu.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. :)

Doh, you are complely right. I had forgot recent meaning change of VM_FAULT_OOM.
yes, this patch is crap. I need to remake it.



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