From 7ffd7a68511c710b84db3548a1997fd2625f580a Mon Sep 17 00:00:00 2001 From: =?utf8?q?Ville=20Syrj=C3=A4l=C3=A4?= Date: Wed, 6 Aug 2014 14:49:44 +0300 Subject: [PATCH] drm: Always reject drm_vblank_get() after drm_vblank_off() MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Reviewed-by: Daniel Vetter Signed-off-by: Ville Syrjälä Signed-off-by: Daniel Vetter --- 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 0de123afdb34..b16a63622bad 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)); -- 2.20.1