Re: Circular vma locking with kvm, seems to be mmu notifiers related

[Avi Kivity <avi@qumranet.com>]

Johannes Weiner wrote:
> Hi Avi,
>
> Avi Kivity <avi@qumranet.com> writes:
>
>   
>> Max Krasnyansky wrote:
>>     
>>> Got this on the latest mainline git.
>>> There are already a couple of lockdep/kvm threads. So maybe it's known.
>>>
>>> =============================================
>>> [ INFO: possible recursive locking detected ]
>>> 2.6.27-rc2 #36
>>> ---------------------------------------------
>>> qemu-system-x86/3445 is trying to acquire lock:
>>>  (&anon_vma->lock){--..}, at: [<ffffffff8029f84d>] mm_take_all_locks+0x8d/0xf0
>>>
>>> but task is already holding lock:
>>>  (&anon_vma->lock){--..}, at: [<ffffffff8029f84d>] mm_take_all_locks+0x8d/0xf0
>>>
>>>   
>>>       
>> Seems to be a false positive.  mmu_take_all_locks takes (surprise!)
>> all anon_vma->locks belonging to an mm, and takes special care not to
>> deadlock while doing this.
>>
>> We need to communicate this to lockdep somehow.
>>     
>
> I think Peter already annotated this in
> 454ed842d55740160334efc9ad56cfef54ed37bc .
>
>   

Excellent, thanks for the info.

-- 
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