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Date: Fri, 13 Jun 2008 09:03:36 +0200
From: Nadia Derbey <Nadia.Derbey@bull.net>
Organization: BULL/DT/OSwR&D/Linux
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To: Andrew Morton <akpm@linux-foundation.org>
Cc: Manfred Spraul <manfred@colorfullife.com>, linux-kernel@vger.kernel.org,
       linux-mm@kvack.org, Pekka Enberg <penberg@cs.helsinki.fi>,
       Christoph Lameter <clameter@sgi.com>
Subject: Re: repeatable slab corruption with LTP msgctl08
References: <20080611221324.42270ef2.akpm@linux-foundation.org>
In-Reply-To: <20080611221324.42270ef2.akpm@linux-foundation.org>
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Andrew Morton wrote:
> Running current mainline on my old 2-way PIII.  Distro is RH FC1.  LTP
> version is ltp-full-20070228 (lots of retro-computing there).
> 
> Config is at http://userweb.kernel.org/~akpm/config-vmm.txt
> 
> 
> ./testcases/bin/msgctl08 crashes after ten minutes or so:
> 
> slab: Internal list corruption detected in cache 'size-128'(26), slabp f2905000(20). Hexdump:
> 
> 000: 00 e0 12 f2 88 32 c0 f7 88 00 00 00 88 50 90 f2
> 010: 14 00 00 00 0f 00 00 00 00 00 00 00 ff ff ff ff
> 020: fd ff ff ff fd ff ff ff fd ff ff ff fd ff ff ff
> 030: fd ff ff ff fd ff ff ff fd ff ff ff fd ff ff ff
> 040: fd ff ff ff fd ff ff ff 00 00 00 00 fd ff ff ff
> 050: fd ff ff ff fd ff ff ff 19 00 00 00 17 00 00 00
> 060: fd ff ff ff fd ff ff ff 0b 00 00 00 fd ff ff ff
> 070: fd ff ff ff fd ff ff ff fd ff ff ff fd ff ff ff
> 080: 10 00 00 00
> ------------[ cut here ]------------
> kernel BUG at mm/slab.c:2949!
> invalid opcode: 0000 [#1] SMP 
> Modules linked in:
> 
> Pid: 3348, comm: msgctl08 Not tainted (2.6.26-rc5 #1)
> EIP: 0060:[<c017a35b>] EFLAGS: 00010086 CPU: 0
> EIP is at check_slabp+0xeb/0x100
> EAX: 00000001 EBX: f2905083 ECX: 00000001 EDX: f20ee670
> ESI: f2905000 EDI: 00000084 EBP: f4671e88 ESP: f4671e64
>  DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
> Process msgctl08 (pid: 3348, ti=f4670000 task=f20ee670 task.ti=f4670000)
> Stack: c0472f2b 00000000 0000001a f2905000 00000014 f7c01500 ffffffff 0000000e 
>        f2905000 f4671eec c017b69f 00000010 000000d0 f20ee670 f7c032ac 000000d0 
>        f7c01500 0000000e f7c03288 f7c06df0 f29ec088 00000098 00000000 00000000 
> Call Trace:
>  [<c017b69f>] ? cache_alloc_refill+0xcf/0x6b0
>  [<c017bdd4>] ? __kmalloc+0x154/0x160
>  [<c0257663>] ? load_msg+0x33/0x150
>  [<c0257663>] ? load_msg+0x33/0x150
>  [<c0257dfb>] ? do_msgsnd+0x17b/0x2e0
>  [<c0257cc9>] ? do_msgsnd+0x49/0x2e0
>  [<c0126f1f>] ? __do_softirq+0x6f/0x100
>  [<c0126e58>] ? _local_bh_enable+0x48/0xa0
>  [<c0257f92>] ? sys_msgsnd+0x32/0x40
>  [<c0106e12>] ? sys_ipc+0xb2/0x240
>  [<c0102f58>] ? sysenter_past_esp+0xa5/0xb1
>  [<c0102f1d>] ? sysenter_past_esp+0x6a/0xb1
>  =======================
> Code: 86 fa ff 8b 55 f0 8b 42 38 8d 04 85 1c 00 00 00 39 f8 76 0b 43 f7 c7 0f 00 00 00 75 d2 eb bd c7 04 24 2b 2f 47 c0 e8 85 86 fa ff <0f> 0b eb fe 83 c4 18 5b 5e 5f 5d c3 8b 56 10 e9 6b ff ff ff 90 
> EIP: [<c017a35b>] check_slabp+0xeb/0x100 SS:ESP 0068:f4671e64
> ---[ end trace d7a2cbbb5a3654be ]---
> 
> 
> Pekka (or Christoph): could you please decrypt the slab bits for us?
> 

Andrew,

Sorry for answering so late (I only saw you e-mail yesterday afternoon).
I have just run msgctl08, setting msgmni to 1722 and turning on the SLAB 
debug:

CONFIG_SLAB=y
CONFIG_SLABINFO=y
CONFIG_DEBUG_SLAB=y
CONFIG_DEBUG_SLAB_LEAK=y

kernel: linux-2.6.26-rc5-mm1
ltp: ltp-full-20080430

But I could not reproduce the bug.

Will try to investigate more.

Regards,
Nadia
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