Re: BUG in 3.19.0-rc3+

[Oded Gabbay <oded.gabbay@amd.com>]

On 01/11/2015 12:57 PM, Chris Clayton wrote:
> Thanks Konstantin.
> 
> [snip]
> 
>>>>
>>>> Looks like degree (%edx) is 1 on anon-vma desruction.
>>>> Probably I've overlooked some weird conrner case in vma splitting/merging.
>>>>
>>>> Could you try this patch. It disables vma merging end eliminates half
>>>> of complicated paths.
>>>> As I see merging is optional, everything should work fine without it.
>>>>
>>>> --- a/mm/mmap.c
>>>> +++ b/mm/mmap.c
>>>> @@ -1048,7 +1048,7 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm,
>>>>          * We later require that vma->vm_flags == vm_flags,
>>>>          * so this tests vma->vm_flags & VM_SPECIAL, too.
>>>>          */
>>>> -       if (vm_flags & VM_SPECIAL)
>>>> +       if (1)
>>>>                 return NULL;
>>>>
>>>>         if (prev)
>>>>
>>>>
>>>>
>>>>
>>>> Code from your oops.
>>>>
>>>> Code: 00 ad de 48 89 43 18 e8 c5 f9 00 00 48 8b 45 10 48 8d 55 10 48
>>>> 83 e8 10 49 39 d6 74 54 48 8b 7d 08 48 89 eb 8b 57 34 85 d2 74 9e <0f>
>>>> 0b 0f 1f 40 00 e8 6b fc ff ff eb 9a 66 0f 1f 84 00 00 00 00
>>>> All code
>>>> ========
>>>>    0: 00 ad de 48 89 43     add    %ch,0x438948de(%rbp)
>>>>    6: 18 e8                 sbb    %ch,%al
>>>>    8: c5 f9 00             (bad)
>>>>    b: 00 48 8b             add    %cl,-0x75(%rax)
>>>>    e: 45 10 48 8d           adc    %r9b,-0x73(%r8)
>>>>   12: 55                   push   %rbp
>>>>   13: 10 48 83             adc    %cl,-0x7d(%rax)
>>>>   16: e8 10 49 39 d6       callq  0xffffffffd639492b
>>>>   1b: 74 54                 je     0x71
>>>>   1d: 48 8b 7d 08           mov    0x8(%rbp),%rdi
>>>>   21: 48 89 eb             mov    %rbp,%rbx
>>>>   24: 8b 57 34             mov    0x34(%rdi),%edx
>>>>   27: 85 d2                 test   %edx,%edx
>>>>   29: 74 9e                 je     0xffffffffffffffc9
>>>>   2b:* 0f 0b                 ud2     <-- trapping instruction
>>>>   2d: 0f 1f 40 00           nopl   0x0(%rax)
>>>>   31: e8 6b fc ff ff       callq  0xfffffffffffffca1
>>>>   36: eb 9a                 jmp    0xffffffffffffffd2
>>>>   38: 66                   data16
>>>>   39: 0f                   .byte 0xf
>>>>   3a: 1f                   (bad)
>>>>   3b: 84 00                 test   %al,(%rax)
>>>>   3d: 00 00                 add    %al,(%rax)
>>>> ...
>>>>
>>>> Code starting with the faulting instruction
>>>> ===========================================
>>>>    0: 0f 0b                 ud2
>>>>    2: 0f 1f 40 00           nopl   0x0(%rax)
>>>>    6: e8 6b fc ff ff       callq  0xfffffffffffffc76
>>>>    b: eb 9a                 jmp    0xffffffffffffffa7
>>>>    d: 66                   data16
>>>>    e: 0f                   .byte 0xf
>>>>    f: 1f                   (bad)
>>>>   10: 84 00                 test   %al,(%rax)
>>>>   12: 00 00                 add    %al,(%rax)
>>>>
>>>>
>>>> +Added Oded Gabbay <oded.gabbay@amd.com> into cc, he's reported this
>>>> problem too.
>>>>
>>> Thanks for the fast reply.
>>>
>>> I applied the patch and tested it. I wasn't able to reproduce *my* problem,
>>> so you are definitely in the right direction :)
>>
>> Ok. I've found something. Try patch from attachment.
>>
> 
> Your patch has fixed the BUG for me. Thank you.
> 
> Tested-by: Chris Clayton <chris2553@googlemail.com>
> 
Same for me. Thanks.

Tested-by: Oded Gabbay <oded.gabbay@amd.com>

	Oded

>>>
>>>         Oded
>>>
>>>>>
>>>>> In case it helps, I've attached the xz-compressed related config file.
>>>>>
>>>>> Chris
>>>>>
>>>>>>
>>>>>> I've attached the full kernel log file for that boot.
>>>>>>
>>>>>> Chris
>>>>>>
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