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.
> -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
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