On 05/28/2014 07:52 PM, Sasha Levin wrote:
> On 05/14/2014 12:35 PM, Peter Zijlstra wrote:
>> On Wed, May 14, 2014 at 12:32:26PM -0400, Sasha Levin wrote:
>>>> -----BEGIN PGP SIGNED MESSAGE-----
>>>> Hash: SHA1
>>>>
>>>> On 05/14/2014 12:29 PM, Peter Zijlstra wrote:
>>>>>> On Mon, May 12, 2014 at 11:42:33AM -0400, Sasha Levin wrote:
>>>>>>>> Hi all,
>>>>>>>>
>>>>>>>> While fuzzing with trinity inside a KVM tools guest running the latest
>>>>>>>> -next kernel I've stumbled on the following spew. Maybe related to the
>>>>>>>> very recent change in freeing on task exit?
>>>>>>>>
>>>>>>>> [ 2509.827261] general protection fault: 0000 [#1] PREEMPT SMP
>>>>>>>> DEBUG_PAGEALLOC [ 2509.830379] Dumping ftrace buffer: [ 2509.830379]
>>>>>>>> (ftrace buffer empty) [ 2509.830379] Modules linked in: [
>>>>>>>> 2509.830379] CPU: 47 PID: 43306 Comm: trinity-c126 Tainted: G W
>>>>>>>> 3.15.0-rc5-next-20140512-sasha-00019-ga20bc00-dirty #456
>>>>>>
>>>>>> Any particular trinity setup? And would you happen to have the seed of
>>>>>> that run?
>>>>
>>>> Nothing special about trinity options. 400 threads and blacklisting some
>>>> of the
>>>> destructive syscalls (umount, reboot, etc).
>>>>
>>>> I don't have the seed, but that problem did reproduce again tonight so I
>>>> can test
>>>> out debug code if you have something in mind.
>> Nah, I drew a pretty big blank, which is why I wanted to see if I could
>> reproduce. If you could share your trinity cmdline I'd be much obliged.
>> While I did manage to clone (the repo moved since last time) and build
>> it, I'm not really that handy with it and want to avoid destroying my
>> machine if possible ;-)
>
> Anything I could do to help out with this? It reproduces pretty easily on my
> configuration so I'd be happy to test out whatever might help.
I've just had this:
[ 591.111854] general protection fault: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
[ 591.121057] Dumping ftrace buffer:
[ 591.121057] (ftrace buffer empty)
[ 591.121057] Modules linked in:
[ 591.121057] CPU: 14 PID: 10272 Comm: trinity-c230 Tainted: G W
3.15.0-rc7-next-20140528-sasha-00019-gd193e91-dirty #545
[ 591.121057] task: ffff8802df0d3000 ti: ffff8802df0fe000 task.ti:
ffff8802df0fe000
[ 591.129130] RIP: perf_event_exit_task (kernel/events/core.c:7492
kernel/events/core.c:7524)
[ 591.129130] RSP: 0000:ffff8802df0ffe28 EFLAGS: 00010246
[ 591.129130] RAX: 0000000000000000 RBX: ffff8802df0d3000 RCX: 0000000000000001
[ 591.129130] RDX: 0000000000000000 RSI: ffffffff97088100 RDI: 0000000000000282
[ 591.129130] RBP: ffff8802df0ffe98 R08: 0000000000000000 R09: 0000000000000000
[ 591.129130] R10: 0000000000000001 R11: 0000000000000000 R12: 6b6b6b6b6b6b6b6b
[ 591.129130] R13: 6b6b6b6b6b6b6b6b R14: ffff8806c9bfd550 R15: 0000000000000001
[ 591.129130] FS: 00007f4b26866700(0000) GS:ffff88036ae00000(0000)
knlGS:0000000000000000
[ 591.129130] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[ 591.129130] CR2: 0000000001a3a9f8 CR3: 000000001702c000 CR4: 00000000000006a0
[ 591.129130] Stack:
[ 591.129130] ffff8802df0ffe48 ffff8802df09cce0 ffff8802fdf99488
ffff8802fdf99290
[ 591.129130] ffff8806c9bfd5a8 ffff8806c9bfd670 ffff8802df0ffe88
6b6b6b6b6b6b6b6b
[ 591.129130] ffff8802df0ffe98 0000000000000001 0000000000000001
ffff8802df0d3000
[ 591.129130] Call Trace:
[ 591.129130] do_exit (kernel/exit.c:766)
[ 591.129130] ? __this_cpu_preempt_check (lib/smp_processor_id.c:63)
[ 591.129130] ? trace_hardirqs_on_caller (kernel/locking/lockdep.c:2557
kernel/locking/lockdep.c:2599)
[ 591.129130] ? trace_hardirqs_on (kernel/locking/lockdep.c:2607)
[ 591.129130] do_group_exit (kernel/exit.c:884)
[ 591.129130] SyS_exit_group (kernel/exit.c:895)
[ 591.129130] tracesys (arch/x86/kernel/entry_64.S:542)
[ 591.129130] Code: a0 02 00 00 49 89 95 a8 02 00 00 4c 8b 45 a0 4c 89 c7 e8 11
c2 2c 03 48 8b 45 a8 48 89 c7 e8 15 7c ff ff 4c 89 ef e8 bd 7b ff ff <49> 8b 45
00 48 89 45 c8 4c 8b 6d c8 e8 cc 19 f6 ff 85 c0 74 0e
All code
========
0: a0 02 00 00 49 89 95 movabs 0x2a8958949000002,%al
7: a8 02
9: 00 00 add %al,(%rax)
b: 4c 8b 45 a0 mov -0x60(%rbp),%r8
f: 4c 89 c7 mov %r8,%rdi
12: e8 11 c2 2c 03 callq 0x32cc228
17: 48 8b 45 a8 mov -0x58(%rbp),%rax
1b: 48 89 c7 mov %rax,%rdi
1e: e8 15 7c ff ff callq 0xffffffffffff7c38
23: 4c 89 ef mov %r13,%rdi
26: e8 bd 7b ff ff callq 0xffffffffffff7be8
2b:* 49 8b 45 00 mov 0x0(%r13),%rax <-- trapping
instruction
2f: 48 89 45 c8 mov %rax,-0x38(%rbp)
33: 4c 8b 6d c8 mov -0x38(%rbp),%r13
37: e8 cc 19 f6 ff callq 0xfffffffffff61a08
3c: 85 c0 test %eax,%eax
3e: 74 0e je 0x4e
...
Code starting with the faulting instruction
===========================================
0: 49 8b 45 00 mov 0x0(%r13),%rax
4: 48 89 45 c8 mov %rax,-0x38(%rbp)
8: 4c 8b 6d c8 mov -0x38(%rbp),%r13
c: e8 cc 19 f6 ff callq 0xfffffffffff619dd
11: 85 c0 test %eax,%eax
13: 74 0e je 0x23
...
[ 591.129130] RIP perf_event_exit_task (kernel/events/core.c:7492
kernel/events/core.c:7524)
[ 591.129130] RSP <ffff8802df0ffe28>
Seems similar enough.
Thanks,
Sasha
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