linux-kernel - Re: OOM killer, page fault

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Date:	Mon, 2 Nov 2009 15:01:10 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Minchan Kim <minchan.kim@...il.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Norbert Preining <preining@...ic.at>,
	linux-kernel@...r.kernel.org, linux-mm <linux-mm@...ck.org>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>
Subject: Re: OOM killer, page fault

On Mon, 2 Nov 2009 14:02:16 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:

> On Mon, 2 Nov 2009 13:56:40 +0900
> Minchan Kim <minchan.kim@...il.com> wrote:
> 
> > On Mon,  2 Nov 2009 13:24:06 +0900 (JST)
> > KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> wrote:
> > 
> > > Hi,
> > > 
> > > (Cc to linux-mm)
> > > 
> > > Wow, this is very strange log.
> > > 
> > > > Dear all,
> > > > 
> > > > (please Cc)
> > > > 
> > > > With 2.6.32-rc5 I got that one:
> > > > [13832.210068] Xorg invoked oom-killer: gfp_mask=0x0, order=0, oom_adj=0
> > > 
> > > order = 0
> > 
> > I think this problem results from 'gfp_mask = 0x0'.
> > Is it possible?
> > 
> > If it isn't H/W problem, Who passes gfp_mask with 0x0?
> > It's culpit. 
> > 
> > Could you add BUG_ON(gfp_mask == 0x0) in __alloc_pages_nodemask's head?
> > 
> 
> Maybe some code returns VM_FAULT_OOM by mistake and pagefault_oom_killer()
> is called. digging mm/memory.c is necessary...
> 
> I wonder why...now is this code
> ===
> static int do_nonlinear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
>                 unsigned long address, pte_t *page_table, pmd_t *pmd,
>                 unsigned int flags, pte_t orig_pte)
> {
>         pgoff_t pgoff;
> 
>         flags |= FAULT_FLAG_NONLINEAR;
> 
> 	if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
>                 return 0;
> 
>         if (unlikely(!(vma->vm_flags & VM_NONLINEAR))) {
>                 /*
>                  * Page table corrupted: show pte and kill process.
>                  */
>                 print_bad_pte(vma, address, orig_pte, NULL);
>                 return VM_FAULT_OOM;
>         }
> 
>         pgoff = pte_to_pgoff(orig_pte);
>         return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
> }
> ==
> Then, OOM...is this really OOM ?

It seems that the goal is to kill process by OOM trick as comment said.

I found It results from Hugh's commit 65500d234e74fc4e8f18e1a429bc24e51e75de4a.
I think it's not a real OOM. 

BTW, If it is culpit in this case, print_bad_pte should have remained any log. :)

> 
> Thanks,
> -Kame
> 


-- 
Kind regards,
Minchan Kim
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