linux-kernel - Re: system death under oom

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Date:	Fri, 29 Mar 2013 16:22:09 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	Ilia Mirkin <imirkin@...m.mit.edu>
Cc:	linux-kernel@...r.kernel.org, nouveau@...ts.freedesktop.org,
	linux-mm@...ck.org
Subject: Re: system death under oom - 3.7.9

On Wed 27-03-13 14:25:36, Ilia Mirkin wrote:
> Hello,
> 
> My system died last night apparently due to OOM conditions. Note that
> I don't have any swap set up, but my understanding is that this is not
> required. The full log is at: http://pastebin.com/YCYUXWvV. It was in
> my messages, so I guess the system took a bit to die completely.

This doesn't seem like OOM:
[615185.810509] DMA32 free:130456kB min:36364kB low:45452kB high:54544kB active_anon:764604kB inactive_anon:13180kB active_file:1282040kB inactive_file:910648kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:3325056kB mlocked:0kB dirty:4472kB writeback:0kB mapped:42836kB shmem:14388kB slab_reclaimable:155160kB slab_unreclaimable:13620kB kernel_stack:576kB pagetables:8712kB unstable:0kB bounce:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no
[615185.810511] lowmem_reserve[]: 0 0 2772 2772
[615185.810517] Normal free:44288kB min:31044kB low:38804kB high:46564kB active_anon:2099560kB inactive_anon:14416kB active_file:271972kB inactive_file:69684kB unevictable:4kB isolated(anon):0kB isolated(file):0kB present:2838528kB mlocked:4kB dirty:12kB writeback:0kB mapped:107868kB shmem:17440kB slab_reclaimable:87304kB slab_unreclaimable:45452kB kernel_stack:3648kB pagetables:42840kB unstable:0kB bounce:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:196 all_unreclaimable? no

You are above above high watermark in the DMA32 zone and slightly bellow
high watermak in the Normal zone.
Your driver requested
[615185.810279] xlock: page allocation failure: order:4, mode:0xc0d0

which is GFP_KERNEL |__GFP_COMP|__GFP_ZERO which doesn't look so unusual but

[615185.810521] DMA: 0*4kB 0*8kB 1*16kB 0*32kB 2*64kB 1*128kB 1*256kB 0*512kB 1*1024kB 1*2048kB 3*4096kB = 15888kB
[615185.810527] DMA32: 5673*4kB 7213*8kB 2142*16kB 461*32kB 30*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 131340kB
[615185.810532] Normal: 3382*4kB 3121*8kB 355*16kB 11*32kB 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 44528kB

but you ran out of high order pages on DMA32 zone (and zone Normal looks
even worse). There are only 30 order-4 pages and I suppose that the
allocation failed on the watermark check for that order.

> nouveau is somewhat implicated, as it is the first thing that hits an
> allocation failure in nouveau_vm_create, and has a subsequent warn in
> nouveau_mm_fini, but then there's a GPF in
> __alloc_skb/__kmalloc_track_caller (and I'm using SLUB). Here is a
> partial disassembly for __kmalloc_track_caller:

I would start by checking whether the driver handles the allocation
failure properly and it doesn't clobber slab data from other allocations
(just a wild guess as I am not familiar with nouveau code at all).

> 
>    0xffffffff811325b1 <+138>:   e8 a0 60 56 00  callq
> 0xffffffff81698656 <__slab_alloc.constprop.68>
>    0xffffffff811325b6 <+143>:   49 89 c4        mov    %rax,%r12
>    0xffffffff811325b9 <+146>:   eb 27   jmp    0xffffffff811325e2
> <__kmalloc_track_caller+187>
>    0xffffffff811325bb <+148>:   49 63 45 20     movslq 0x20(%r13),%rax
>    0xffffffff811325bf <+152>:   48 8d 4a 01     lea    0x1(%rdx),%rcx
>    0xffffffff811325c3 <+156>:   49 8b 7d 00     mov    0x0(%r13),%rdi
>    0xffffffff811325c7 <+160>:   49 8b 1c 04     mov    (%r12,%rax,1),%rbx
>    0xffffffff811325cb <+164>:   4c 89 e0        mov    %r12,%rax
>    0xffffffff811325ce <+167>:   48 8d 37        lea    (%rdi),%rsi
>    0xffffffff811325d1 <+170>:   e8 3a 38 1b 00  callq
> 0xffffffff812e5e10 <this_cpu_cmpxchg16b_emu>
> 
> The GPF happens at +160, which is in the argument setup for the
> cmpxchg in slab_alloc_node. I think it's the call to
> get_freepointer(). There was a similar bug report a while back,
> https://lkml.org/lkml/2011/5/23/199, and the recommendation was to run
> with slub debugging. Is that still the case, or is there a simpler
> explanation? I can't reproduce this at will, not sure how many times
> this has happened but definitely not many.
> 
>   -ilia
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-- 
Michal Hocko
SUSE Labs
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