1 files changed, 54 insertions, 14 deletions

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 83cce0cdb769..4b91228fd9bd 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -1469,6 +1469,34 @@ static irqreturn_t ironlake_irq_handler(int irq, void *arg)
         return ret;
 }
 
+static void i915_error_wake_up(struct drm_i915_private *dev_priv,
+                               bool reset_completed)
+{
+        struct intel_ring_buffer *ring;
+        int i;
+
+        /*
+         * Notify all waiters for GPU completion events that reset state has
+         * been changed, and that they need to restart their wait after
+         * checking for potential errors (and bail out to drop locks if there is
+         * a gpu reset pending so that i915_error_work_func can acquire them).
+         */
+
+        /* Wake up __wait_seqno, potentially holding dev->struct_mutex. */
+        for_each_ring(ring, dev_priv, i)
+                wake_up_all(&ring->irq_queue);
+
+        /* Wake up intel_crtc_wait_for_pending_flips, holding crtc->mutex. */
+        wake_up_all(&dev_priv->pending_flip_queue);
+
+        /*
+         * Signal tasks blocked in i915_gem_wait_for_error that the pending
+         * reset state is cleared.
+         */
+        if (reset_completed)
+                wake_up_all(&dev_priv->gpu_error.reset_queue);
+}
+
 /**
  * i915_error_work_func - do process context error handling work
  * @work: work struct
@@ -1483,11 +1511,10 @@ static void i915_error_work_func(struct work_struct *work)
         drm_i915_private_t *dev_priv = container_of(error, drm_i915_private_t,
                                                     gpu_error);
         struct drm_device *dev = dev_priv->dev;
-        struct intel_ring_buffer *ring;
         char *error_event[] = { I915_ERROR_UEVENT "=1", NULL };
         char *reset_event[] = { I915_RESET_UEVENT "=1", NULL };
         char *reset_done_event[] = { I915_ERROR_UEVENT "=0", NULL };
-        int i, ret;
+        int ret;
 
         kobject_uevent_env(&dev->primary->kdev.kobj, KOBJ_CHANGE, error_event);
 
@@ -1506,8 +1533,16 @@ static void i915_error_work_func(struct work_struct *work)
                 kobject_uevent_env(&dev->primary->kdev.kobj, KOBJ_CHANGE,
                                    reset_event);
 
+                /*
+                 * All state reset _must_ be completed before we update the
+                 * reset counter, for otherwise waiters might miss the reset
+                 * pending state and not properly drop locks, resulting in
+                 * deadlocks with the reset work.
+                 */
                 ret = i915_reset(dev);
 
+                intel_display_handle_reset(dev);
+
                 if (ret == 0) {
                         /*
                          * After all the gem state is reset, increment the reset
@@ -1528,12 +1563,11 @@ static void i915_error_work_func(struct work_struct *work)
                         atomic_set(&error->reset_counter, I915_WEDGED);
                 }
 
-                for_each_ring(ring, dev_priv, i)
-                        wake_up_all(&ring->irq_queue);
-
-                intel_display_handle_reset(dev);
-
-                wake_up_all(&dev_priv->gpu_error.reset_queue);
+                /*
+                 * Note: The wake_up also serves as a memory barrier so that
+                 * waiters see the update value of the reset counter atomic_t.
+                 */
+                i915_error_wake_up(dev_priv, true);
         }
 }
 
@@ -1642,8 +1676,6 @@ static void i915_report_and_clear_eir(struct drm_device *dev)
 void i915_handle_error(struct drm_device *dev, bool wedged)
 {
         struct drm_i915_private *dev_priv = dev->dev_private;
-        struct intel_ring_buffer *ring;
-        int i;
 
         i915_capture_error_state(dev);
         i915_report_and_clear_eir(dev);
@@ -1653,11 +1685,19 @@ void i915_handle_error(struct drm_device *dev, bool wedged)
                                 &dev_priv->gpu_error.reset_counter);
 
                 /*
-                 * Wakeup waiting processes so that the reset work item
-                 * doesn't deadlock trying to grab various locks.
+                 * Wakeup waiting processes so that the reset work function
+                 * i915_error_work_func doesn't deadlock trying to grab various
+                 * locks. By bumping the reset counter first, the woken
+                 * processes will see a reset in progress and back off,
+                 * releasing their locks and then wait for the reset completion.
+                 * We must do this for _all_ gpu waiters that might hold locks
+                 * that the reset work needs to acquire.
+                 *
+                 * Note: The wake_up serves as the required memory barrier to
+                 * ensure that the waiters see the updated value of the reset
+                 * counter atomic_t.
                  */
-                for_each_ring(ring, dev_priv, i)
-                        wake_up_all(&ring->irq_queue);
+                i915_error_wake_up(dev_priv, false);
         }
 
         /*