On Mon, May 26, 2014 at 04:32:02PM +0300, Ville Syrjälä wrote:
> On Mon, May 26, 2014 at 03:21:41PM +0200, Daniel Vetter wrote:
> > On Mon, May 26, 2014 at 02:46:24PM +0300, ville.syrjala@xxxxxxxxxxxxxxx wrote:
> > > From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> > >
> > > Make sure drm_vblank_get() never succeeds when called between
> > > drm_vblank_off() and drm_vblank_on(). Borrow a trick from the
> > > old drm_vblank_{pre,post}_modeset() functions and just bump
> > > the refcount in drm_vblank_off() and drop it in drm_vblank_on().
> > >
> > > Hopefully the use of inmodeset won't conflict badly with
> > > drm_vblank_{pre,post}_modeset().
> > >
> > > For i915 there's a window between drm_vblank_off() and marking the
> > > crtc as inactive where the current code still allows drm_vblank_get().
> > >
> > > Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> >
> > Afaics we never check anywhere for inmodeset in drm_vblank_get, so how
> > does this work?
>
> If refcount is already >0 and vblank irq is disabled, drm_vblank_get() will
> return -EINVAL.
Oh right, I've missed that. drm_irq.c is never short of suprises. With
that enlightenment (and maybe a pimped commit message for blind people
like me) this is Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
>
> > -Daniel
> >
> > > ---
> > > drivers/gpu/drm/drm_irq.c | 14 ++++++++++++++
> > > 1 file changed, 14 insertions(+)
> > >
> > > diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
> > > index b565372..7b1e08c 100644
> > > --- a/drivers/gpu/drm/drm_irq.c
> > > +++ b/drivers/gpu/drm/drm_irq.c
> > > @@ -1039,6 +1039,15 @@ void drm_vblank_off(struct drm_device *dev, int crtc)
> > > }
> > > spin_unlock(&dev->event_lock);
> > >
> > > + /*
> > > + * Prevent subsequent drm_vblank_get() from re-enabling
> > > + * the vblank interrupt by bumping the refcount.
> > > + */
> > > + if (!dev->vblank[crtc].inmodeset) {
> > > + atomic_inc(&dev->vblank[crtc].refcount);
> > > + dev->vblank[crtc].inmodeset = 1;
> > > + }
> > > +
> > > spin_unlock_irqrestore(&dev->vbl_lock, irqflags);
> > > }
> > > EXPORT_SYMBOL(drm_vblank_off);
> > > @@ -1079,6 +1088,11 @@ void drm_vblank_on(struct drm_device *dev, int crtc)
> > > unsigned long irqflags;
> > >
> > > spin_lock_irqsave(&dev->vbl_lock, irqflags);
> > > + /* Drop our private "prevent drm_vblank_get" refcount */
> > > + if (dev->vblank[crtc].inmodeset) {
> > > + atomic_dec(&dev->vblank[crtc].refcount);
> > > + dev->vblank[crtc].inmodeset = 0;
> > > + }
> > > /* re-enable interrupts if there's are users left */
> > > if (atomic_read(&dev->vblank[crtc].refcount) != 0)
> > > WARN_ON(drm_vblank_enable(dev, crtc));
> > > --
> > > 1.8.5.5
> > >
> > > _______________________________________________
> > > Intel-gfx mailing list
> > > Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> > > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
> >
> > --
> > Daniel Vetter
> > Software Engineer, Intel Corporation
> > +41 (0) 79 365 57 48 - http://blog.ffwll.ch
>
> --
> Ville Syrjälä
> Intel OTC
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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