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@linux.intel.com wrote:
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().
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@linux.intel.com
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
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-- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch