drm/radeon: rework locking ring emission mutex in fence deadlock detection v2

Some callers illegal called fence_wait_next/empty
while holding the ring emission mutex. So don't
relock the mutex in that cases, and move the actual
locking into the fence code.

v2: Don't try to unlock the mutex if it isn't locked.
Signed-off-by: Christian König <deathsimple@vodafone.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/radeon.h

@@ -284,8 +284,8 @@ int radeon_fence_emit(struct radeon_device *rdev, struct radeon_fence *fence);
 void radeon_fence_process(struct radeon_device *rdev, int ring);
 bool radeon_fence_signaled(struct radeon_fence *fence);
 int radeon_fence_wait(struct radeon_fence *fence, bool interruptible);
-int radeon_fence_wait_next(struct radeon_device *rdev, int ring);
-int radeon_fence_wait_empty(struct radeon_device *rdev, int ring);
+int radeon_fence_wait_next_locked(struct radeon_device *rdev, int ring);
+int radeon_fence_wait_empty_locked(struct radeon_device *rdev, int ring);
 struct radeon_fence *radeon_fence_ref(struct radeon_fence *fence);
 void radeon_fence_unref(struct radeon_fence **fence);
 unsigned radeon_fence_count_emitted(struct radeon_device *rdev, int ring);

drivers/gpu/drm/radeon/radeon_device.c

@@ -912,9 +912,12 @@ int radeon_suspend_kms(struct drm_device *dev, pm_message_t state)
 	}
 	/* evict vram memory */
 	radeon_bo_evict_vram(rdev);
+
+	mutex_lock(&rdev->ring_lock);
 	/* wait for gpu to finish processing current batch */
 	for (i = 0; i < RADEON_NUM_RINGS; i++)
-		radeon_fence_wait_empty(rdev, i);
+		radeon_fence_wait_empty_locked(rdev, i);
+	mutex_unlock(&rdev->ring_lock);
 
 	radeon_save_bios_scratch_regs(rdev);
 

drivers/gpu/drm/radeon/radeon_fence.c

@@ -194,7 +194,7 @@ bool radeon_fence_signaled(struct radeon_fence *fence)
 }
 
 static int radeon_fence_wait_seq(struct radeon_device *rdev, u64 target_seq,
-				 unsigned ring, bool intr)
+				 unsigned ring, bool intr, bool lock_ring)
 {
 	unsigned long timeout, last_activity;
 	uint64_t seq;
@@ -249,8 +249,16 @@ static int radeon_fence_wait_seq(struct radeon_device *rdev, u64 target_seq,
 			if (seq != atomic64_read(&rdev->fence_drv[ring].last_seq)) {
 				continue;
 			}
+
+			if (lock_ring) {
+				mutex_lock(&rdev->ring_lock);
+			}
+
 			/* test if somebody else has already decided that this is a lockup */
 			if (last_activity != rdev->fence_drv[ring].last_activity) {
+				if (lock_ring) {
+					mutex_unlock(&rdev->ring_lock);
+				}
 				continue;
 			}
 
@@ -264,15 +272,17 @@ static int radeon_fence_wait_seq(struct radeon_device *rdev, u64 target_seq,
 					rdev->fence_drv[i].last_activity = jiffies;
 				}
 
-				/* change last activity so nobody else think there is a lockup */
-				for (i = 0; i < RADEON_NUM_RINGS; ++i) {
-					rdev->fence_drv[i].last_activity = jiffies;
-				}
-
 				/* mark the ring as not ready any more */
 				rdev->ring[ring].ready = false;
+				if (lock_ring) {
+					mutex_unlock(&rdev->ring_lock);
+				}
 				return -EDEADLK;
 			}
+
+			if (lock_ring) {
+				mutex_unlock(&rdev->ring_lock);
+			}
 		}
 	}
 	return 0;
@@ -287,7 +297,8 @@ int radeon_fence_wait(struct radeon_fence *fence, bool intr)
 		return -EINVAL;
 	}
 
-	r = radeon_fence_wait_seq(fence->rdev, fence->seq, fence->ring, intr);
+	r = radeon_fence_wait_seq(fence->rdev, fence->seq,
+				  fence->ring, intr, true);
 	if (r) {
 		return r;
 	}
@@ -295,7 +306,7 @@ int radeon_fence_wait(struct radeon_fence *fence, bool intr)
 	return 0;
 }
 
-int radeon_fence_wait_next(struct radeon_device *rdev, int ring)
+int radeon_fence_wait_next_locked(struct radeon_device *rdev, int ring)
 {
 	uint64_t seq;
 
@@ -305,20 +316,22 @@ int radeon_fence_wait_next(struct radeon_device *rdev, int ring)
 	 */
 	seq = atomic64_read(&rdev->fence_drv[ring].last_seq) + 1ULL;
 	if (seq >= rdev->fence_drv[ring].seq) {
-		/* nothing to wait for, last_seq is already the last emited fence */
-		return 0;
+		/* nothing to wait for, last_seq is
+		   already the last emited fence */
+		return -ENOENT;
 	}
-	return radeon_fence_wait_seq(rdev, seq, ring, false);
+	return radeon_fence_wait_seq(rdev, seq, ring, false, false);
 }
 
-int radeon_fence_wait_empty(struct radeon_device *rdev, int ring)
+int radeon_fence_wait_empty_locked(struct radeon_device *rdev, int ring)
 {
 	/* We are not protected by ring lock when reading current seq
 	 * but it's ok as wait empty is call from place where no more
 	 * activity can be scheduled so there won't be concurrent access
 	 * to seq value.
 	 */
-	return radeon_fence_wait_seq(rdev, rdev->fence_drv[ring].seq, ring, false);
+	return radeon_fence_wait_seq(rdev, rdev->fence_drv[ring].seq,
+				     ring, false, false);
 }
 
 struct radeon_fence *radeon_fence_ref(struct radeon_fence *fence)
@@ -410,14 +423,16 @@ void radeon_fence_driver_fini(struct radeon_device *rdev)
 {
 	int ring;
 
+	mutex_lock(&rdev->ring_lock);
 	for (ring = 0; ring < RADEON_NUM_RINGS; ring++) {
 		if (!rdev->fence_drv[ring].initialized)
 			continue;
-		radeon_fence_wait_empty(rdev, ring);
+		radeon_fence_wait_empty_locked(rdev, ring);
 		wake_up_all(&rdev->fence_drv[ring].queue);
 		radeon_scratch_free(rdev, rdev->fence_drv[ring].scratch_reg);
 		rdev->fence_drv[ring].initialized = false;
 	}
+	mutex_unlock(&rdev->ring_lock);
 }
 
 

drivers/gpu/drm/radeon/radeon_pm.c

@@ -270,13 +270,7 @@ static void radeon_pm_set_clocks(struct radeon_device *rdev)
 	} else {
 		struct radeon_ring *ring = &rdev->ring[RADEON_RING_TYPE_GFX_INDEX];
 		if (ring->ready) {
-			struct radeon_fence *fence;
-			radeon_ring_alloc(rdev, ring, 64);
-			radeon_fence_create(rdev, &fence, radeon_ring_index(rdev, ring));
-			radeon_fence_emit(rdev, fence);
-			radeon_ring_commit(rdev, ring);
-			radeon_fence_wait(fence, false);
-			radeon_fence_unref(&fence);
+			radeon_fence_wait_empty_locked(rdev, RADEON_RING_TYPE_GFX_INDEX);
 		}
 	}
 	radeon_unmap_vram_bos(rdev);

drivers/gpu/drm/radeon/radeon_ring.c

@@ -347,9 +347,7 @@ int radeon_ring_alloc(struct radeon_device *rdev, struct radeon_ring *ring, unsi
 		if (ndw < ring->ring_free_dw) {
 			break;
 		}
-		mutex_unlock(&rdev->ring_lock);
-		r = radeon_fence_wait_next(rdev, radeon_ring_index(rdev, ring));
-		mutex_lock(&rdev->ring_lock);
+		r = radeon_fence_wait_next_locked(rdev, radeon_ring_index(rdev, ring));
 		if (r)
 			return r;
 	}
@@ -408,7 +406,6 @@ void radeon_ring_force_activity(struct radeon_device *rdev, struct radeon_ring *
 {
 	int r;
 
-	mutex_lock(&rdev->ring_lock);
 	radeon_ring_free_size(rdev, ring);
 	if (ring->rptr == ring->wptr) {
 		r = radeon_ring_alloc(rdev, ring, 1);
@@ -417,7 +414,6 @@ void radeon_ring_force_activity(struct radeon_device *rdev, struct radeon_ring *
 			radeon_ring_commit(rdev, ring);
 		}
 	}
-	mutex_unlock(&rdev->ring_lock);
 }
 
 void radeon_ring_lockup_update(struct radeon_ring *ring)