Jiri Olsa wrote:
quoted text
> Jiri Kosina wrote:
>> On Mon, 3 Mar 2008, Jiri Olsa wrote:
>>
>>> your patch with LOCKDEP enabled:
>>> ipcs.strace.1		- strace of ipcs from the first run
>>> ipcs.kernel.out.1 	- kernel logs from 1st strace ipcs run
>>> [   49.465371] info: dee9fca4
>>> [   49.465397] BUG: unable to handle kernel NULL pointer dereference at virtual address 000000bf
>>> [   49.465411] printing eip: c0133034 *pde = 00000000
>>> [   49.465432] Oops: 0002 [#1]
>>> [   49.465445] Modules linked in: netconsole i915 drm configfs e1000 snd_intel8x0 snd_ac97_codec ac97_bus snd_pcm snd_timer snd snd_page_alloc
>>> [   49.465534]
>>> [   49.465542] Pid: 4763, comm: ipcs Not tainted (2.6.24.3test-dirty #22)
>>> [   49.465550] EIP: 0060:[<c0133034>] EFLAGS: 00010086 CPU: 0
>>> [   49.465568] EIP is at __lock_acquire+0x319/0xc20
>>> [   49.465575] EAX: 00000002 EBX: 00000246 ECX: dee9fcb4 EDX: 00000002
>>> [   49.465583] ESI: ffffffff EDI: 00000000 EBP: d8c9fe74 ESP: d8c9fe18
>>> [   49.465591]  DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 0068
>>> [   49.465599] Process ipcs (pid: 4763, ti=d8c9e000 task=d8d181b0 task.ti=d8c9e000)
>>> [   49.465606] Stack: 00000012 c0456032 d8c9fea4 00000246 d8c9fe66 c03875bc 00000002 00000000
>>> [   49.465667]        00000000 dee9fcb4 845dad28 d8d181b0 00000031 00000000 000001e1 00000246
>>> [   49.465731]        00000021 845dad28 1bbd0328 373c0000 00000246 00000000 00000000 d8c9fe9c
>>> [   49.465792] Call Trace:
>>> [   49.465803]  [<c0103e9f>] show_trace_log_lvl+0x1a/0x2f
>>> [   49.465820]  [<c0103f51>] show_stack_log_lvl+0x9d/0xa5
>>> [   49.465841]  [<c0104006>] show_registers+0xad/0x17c
>>> [   49.465859]  [<c01041cc>] die+0xf7/0x1c8
>>> [   49.465872]  [<c0110e31>] do_page_fault+0x464/0x54b
>>> [   49.465886]  [<c030108a>] error_code+0x6a/0x70
>>> [   49.465904]  [<c01339b3>] lock_acquire+0x78/0x91
>>> [   49.465918]  [<c0300a55>] _spin_lock+0x2e/0x58
>>> [   49.465931]  [<c01b8e91>] sys_shmctl+0x70b/0x78a
>>> [   49.465947]  [<c0106d33>] sys_ipc+0x19f/0x1b5
>>> [   49.465964]  [<c0102fa6>] syscall_call+0x7/0xb
>>> [   49.465977]  =======================
>>> [   49.465984] Code: 00 85 c0 0f 84 1d 09 00 00 83 3d 00 bf 6f c0 00 0f 85 
>>> 10 09 00 00 c7 44 24 0c c8 8b 30 c0 c7 44 24 08 26 03 00 00 e9 8b 07 00 
>>> 00 <ff> 86 c0 00 00 00 8b 45 d0 8b 80 54 06 00 00 83 f8 1d 89 45 cc
>> OK, so the actual NULL pointer dereference happens inside atomic_inc(), 
>> during incrementing of counter->v (as %esi == 0xffffffff). So apparently 
>> someone corrupted spinlock_t for shmem_inode_info.lock, which is being 
>> obtained in shm_get_stat().
>>
> 
> I'm striping down the config to hopefully find out the cause...
> anything else I can try? besides code study :)
> 
> thanks

I found a configuration which works for me, attaching both configs, bad and good one
hope this helps