VM lockdep warning

[Dave Airlie]

2012/4/21 Jerome Glisse <j.glisse at gmail.com>:
> 2012/4/21 Christian König <deathsimple at vodafone.de>:
>> On 21.04.2012 16:08, Jerome Glisse wrote:
>>>
>>> 2012/4/21 Christian König<deathsimple at vodafone.de>:
>>>>
>>>> Interesting, I'm pretty sure that I haven't touched the locking order of
>>>> the
>>>> cs_mutex vs. vm_mutex.
>>>>
>>>> Maybe it is just some kind of side effect, going to locking into it
>>>> anyway.
>>>>
>>>> Christian.
>>>>
>>> It's the using, init path take lock in different order than cs path
>>
>> Well, could you explain to me why the vm code takes cs mutex in the first
>> place?
>>
>> It clearly has it's own mutex and it doesn't looks like that it deals with
>> any cs related data anyway.
>>
>> Christian.
>
> Lock simplification is on my todo. The issue is that vm manager is protected by
> cs_mutex The vm.mutex is specific to each vm it doesn't protect the global vm
> management. I didn't wanted to introduce a new global vm mutex as vm activity
> is mostly trigger on behalf of cs so i dediced to use the cs mutex.
>
> That's why non cs path of vm need to take the cs mutex.

So if one app is adding a bo, and another doing CS, isn't deadlock a
real possibility?

I expect the VM code need to take CS mutex earlier then.

Dave.