1 files changed, 15 insertions, 16 deletions

diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index cb3794a00f98..44a5d0ad8b7c 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -110,10 +110,7 @@ static void vblank_disable_and_save(struct drm_device *dev, int crtc)
         /* Prevent vblank irq processing while disabling vblank irqs,
          * so no updates of timestamps or count can happen after we've
          * disabled. Needed to prevent races in case of delayed irq's.
-         * Disable preemption, so vblank_time_lock is held as short as
-         * possible, even under a kernel with PREEMPT_RT patches.
          */
-        preempt_disable();
         spin_lock_irqsave(&dev->vblank_time_lock, irqflags);
 
         dev->driver->disable_vblank(dev, crtc);
@@ -164,7 +161,6 @@ static void vblank_disable_and_save(struct drm_device *dev, int crtc)
         clear_vblank_timestamps(dev, crtc);
 
         spin_unlock_irqrestore(&dev->vblank_time_lock, irqflags);
-        preempt_enable();
 }
 
 static void vblank_disable_fn(unsigned long arg)
@@ -407,13 +403,16 @@ int drm_irq_uninstall(struct drm_device *dev)
         /*
          * Wake up any waiters so they don't hang.
          */
-        spin_lock_irqsave(&dev->vbl_lock, irqflags);
-        for (i = 0; i < dev->num_crtcs; i++) {
-                DRM_WAKEUP(&dev->vbl_queue[i]);
-                dev->vblank_enabled[i] = 0;
-                dev->last_vblank[i] = dev->driver->get_vblank_counter(dev, i);
+        if (dev->num_crtcs) {
+                spin_lock_irqsave(&dev->vbl_lock, irqflags);
+                for (i = 0; i < dev->num_crtcs; i++) {
+                        DRM_WAKEUP(&dev->vbl_queue[i]);
+                        dev->vblank_enabled[i] = 0;
+                        dev->last_vblank[i] =
+                                dev->driver->get_vblank_counter(dev, i);
+                }
+                spin_unlock_irqrestore(&dev->vbl_lock, irqflags);
         }
-        spin_unlock_irqrestore(&dev->vbl_lock, irqflags);
 
         if (!irq_enabled)
                 return -EINVAL;
@@ -886,10 +885,6 @@ int drm_vblank_get(struct drm_device *dev, int crtc)
         spin_lock_irqsave(&dev->vbl_lock, irqflags);
         /* Going from 0->1 means we have to enable interrupts again */
         if (atomic_add_return(1, &dev->vblank_refcount[crtc]) == 1) {
-                /* Disable preemption while holding vblank_time_lock. Do
-                 * it explicitely to guard against PREEMPT_RT kernel.
-                 */
-                preempt_disable();
                 spin_lock_irqsave(&dev->vblank_time_lock, irqflags2);
                 if (!dev->vblank_enabled[crtc]) {
                         /* Enable vblank irqs under vblank_time_lock protection.
@@ -909,7 +904,6 @@ int drm_vblank_get(struct drm_device *dev, int crtc)
                         }
                 }
                 spin_unlock_irqrestore(&dev->vblank_time_lock, irqflags2);
-                preempt_enable();
         } else {
                 if (!dev->vblank_enabled[crtc]) {
                         atomic_dec(&dev->vblank_refcount[crtc]);
@@ -1125,6 +1119,7 @@ static int drm_queue_vblank_event(struct drm_device *dev, int pipe,
                 trace_drm_vblank_event_delivered(current->pid, pipe,
                                                  vblwait->request.sequence);
         } else {
+                /* drm_handle_vblank_events will call drm_vblank_put */
                 list_add_tail(&e->base.link, &dev->vblank_event_list);
                 vblwait->reply.sequence = vblwait->request.sequence;
         }
@@ -1205,8 +1200,12 @@ int drm_wait_vblank(struct drm_device *dev, void *data,
                 goto done;
         }
 
-        if (flags & _DRM_VBLANK_EVENT)
+        if (flags & _DRM_VBLANK_EVENT) {
+                /* must hold on to the vblank ref until the event fires
+                 * drm_vblank_put will be called asynchronously
+                 */
                 return drm_queue_vblank_event(dev, crtc, vblwait, file_priv);
+        }
 
         if ((flags & _DRM_VBLANK_NEXTONMISS) &&
             (seq - vblwait->request.sequence) <= (1<<23)) {