[Intel-gfx] [PATCH] drm/i915: reset forcewake count after reset

[Ben Widawsky]

On Thu, Jun 23, 2011 at 07:00:50PM -0700, Ben Widawsky wrote:
> On Fri, Jun 24, 2011 at 12:45:27AM +0100, Chris Wilson wrote:
> > On Thu, 23 Jun 2011 16:06:22 -0700, Ben Widawsky <ben at bwidawsk.net> wrote:
> > > 
> > > Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
> > > ---
> > >  drivers/gpu/drm/i915/i915_drv.c |    1 +
> > >  1 files changed, 1 insertions(+), 0 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> > > index 0defd42..9292499 100644
> > > --- a/drivers/gpu/drm/i915/i915_drv.c
> > > +++ b/drivers/gpu/drm/i915/i915_drv.c
> > > @@ -579,6 +579,7 @@ int i915_reset(struct drm_device *dev, u8 flags)
> > >  	} else switch (INTEL_INFO(dev)->gen) {
> > >  	case 6:
> > >  		ret = gen6_do_reset(dev, flags);
> > > +		atomic_set(&dev_priv->forcewake_count, 0);
> > >  		break;
> > >  	case 5:
> > >  		ret = ironlake_do_reset(dev, flags);
> > 
> > Can forcewake be non-zero here? If it has been bumped by a user wakelock,
> > then what happens when that is subsequently released? I don't think this
> > is safe...
> > 
> > What scenario are you trying to fix?
> > -Chris
> 
> This is not the cleanest fix, but the problem is the following:
> 
> 1. User bumps refcount
> 2. GPU hangs
> 3. Reset occurs
> 4. User doesn't close the file (or even the race before the user closes
>    the file after the reset) the driver is now completely screwed in
>    this case, once the user does close the file, things will go back to
>    normal.
> 
> I was actually just about to respond to my original email to say this
> belongs in -fixes (unless I'm confused).
> 
> Ben

Just realized that you're right. My code is buggy at step 4 when the
user closes the file... I do think we need some fix though. Agree?