[Nouveau] [PATCH 1/3] drm/nouveau: fix vblank interrupt being called before event is setup

[Ben Skeggs]

On Tue, Jul 30, 2013 at 4:10 PM, Maarten Lankhorst
<maarten.lankhorst at canonical.com> wrote:
> Op 30-07-13 04:42, Ben Skeggs schreef:
>> On Tue, Jul 23, 2013 at 11:43 PM, Maarten Lankhorst
>> <maarten.lankhorst at canonical.com> wrote:
>>> Sort of fixes mmiotrace for me again, I could sear I sent a similar patch before
>>> the rework to event interface, so I guess it got reintroduced.
>> I don't know how/why you think this fixes anything.  The interrupt
>> handler can't possibly be called until after priv->base.vblank has
>> been initialised...
>>
>> Seriously, go look, the subdev interrupt handler pointer isn't filled
>> in (and can't be) until after nouveau_disp_create() has been called,
>> and nouveau_disp_create() initialises priv->base.vblank before it
>> returns...
>>
> There's also a disp_dtor function right above it and without a smp_wmb
> the writes could still be reordered in the constructor. O:-) A spinlock would
> be needed to make sure that no interrupt is in process if you set intr to null
> before destroying vblank event, though.
>
> I can probably try to get the oops again indicating that priv->base.vblank was null in the interrupt handler if you want,
> iirc it happened reliably during mmiotracing.
It would've had to have happened during a module unload in that case,
I can't see how else it could've possibly happened.

The destructor case is valid though, but not really a critical issue,
so I'd rather find a better solution than these hacked checks :)  I'll
add it to the list...

Ben.

>
> ~Maarten