linux-kernel - Re: OOM killer, page fault

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Date:	Mon, 2 Nov 2009 14:02:16 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Minchan Kim <minchan.kim@...il.com>
Cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Norbert Preining <preining@...ic.at>,
	linux-kernel@...r.kernel.org, linux-mm <linux-mm@...ck.org>
Subject: Re: OOM killer, page fault

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 ?

Thanks,
-Kame

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