[PATCH 1/3] drm/radeon: move ring locking out of reset path

[Christian König]

On 02.07.2012 17:41, Jerome Glisse wrote:
> On Fri, Jun 29, 2012 at 12:15 PM, Michel Dänzer <michel at daenzer.net> wrote:
>> On Fre, 2012-06-29 at 17:18 +0200, Christian König wrote:
>>> On 29.06.2012 17:09, Michel Dänzer wrote:
>>>> On Fre, 2012-06-29 at 16:45 +0200, Christian König wrote:
>>>>> Hold the ring lock the whole time the reset is in progress,
>>>>> otherwise another process can submit new jobs.
>>>> Sounds good, but doesn't this create other paths (e.g. initialization,
>>>> resume) where the ring is being accessed without holding the lock? Isn't
>>>> that a problem?
>>> Thought about that also.
>>>
>>> For init I'm pretty sure that no application can submit commands before
>>> we are done, otherwise we are doomed anyway.
>>>
>>> For resume I'm not really sure, but I think that applications are
>>> resumed after the hardware driver had a chance of doing so.
>> I hope you're right... but if it's not too much trouble, it might be
>> better to be safe than sorry and take the lock for those paths as well.
>>
>>
> NAK this is the wrong way to solve the issue, we need a global lock on
> all path that can trigger gpu activities. Previously it was the cs
> mutex, but i haven't thought about it too much when it got removed. So
> to fix the situation i am sending a patch with rw semaphore.
So what I'm missing? What else can trigger GPU activity when not the rings?

I'm currently working on ring-partial resets and also resets where you 
only skip over a single faulty IB instead of flushing the whole ring. 
And my current idea for that to work is that we hold the ring lock while 
we do suspend, ring_save, asic_reset, resume and ring_restore.

Christian.

>
> Cheers,
> Jerome
>