From: Ville Syrjälä ville.syrjala@linux.intel.com
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().
When drm_vblank_get() encounters a >0 refcount and the vblank interrupt is already disabled it will simply return -EINVAL.
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().
v2: Describe what drm_vblank_get() does to explain how a simple refcount bump manages to fix things (Daniel)
Reviewed-by: Matt Roper matthew.d.roper@intel.com Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch Signed-off-by: Ville Syrjälä ville.syrjala@linux.intel.com --- 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 0de123a..b16a636 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));