drm/radeon: avoid deadlock if GPU lockup is detected in ib_pool_get

If GPU lockup is detected in ib_pool get we are holding the ib_pool
mutex that will be needed by the GPU reset code. As ib_pool code is
safe to be reentrant from GPU reset code we should not block if we
are trying to get the ib pool lock on the behalf of the same userspace
caller, thus use the radeon_mutex_lock helper.

Signed-off-by: Jerome Glisse <[e-mail]>
Signed-off-by: Dave Airlie <[e-mail]>

drivers/gpu/drm/radeon/radeon.h

···
 
 
 /*
+ * Mutex which allows recursive locking from the same process.
+ */
+struct radeon_mutex {
+	struct mutex		mutex;
+	struct task_struct	*owner;
+	int			level;
+};
+
+static inline void radeon_mutex_init(struct radeon_mutex *mutex)
+{
+	mutex_init(&mutex->mutex);
+	mutex->owner = NULL;
+	mutex->level = 0;
+}
+
+static inline void radeon_mutex_lock(struct radeon_mutex *mutex)
+{
+	if (mutex_trylock(&mutex->mutex)) {
+		/* The mutex was unlocked before, so it's ours now */
+		mutex->owner = current;
+	} else if (mutex->owner != current) {
+		/* Another process locked the mutex, take it */
+		mutex_lock(&mutex->mutex);
+		mutex->owner = current;
+	}
+	/* Otherwise the mutex was already locked by this process */
+
+	mutex->level++;
+}
+
+static inline void radeon_mutex_unlock(struct radeon_mutex *mutex)
+{
+	if (--mutex->level > 0)
+		return;
+
+	mutex->owner = NULL;
+	mutex_unlock(&mutex->mutex);
+}
+
+
+/*
  * Dummy page
  */
 struct radeon_dummy_page {
···
  * mutex protects scheduled_ibs, ready, alloc_bm
  */
 struct radeon_ib_pool {
-	struct mutex			mutex;
+	struct radeon_mutex		mutex;
 	struct radeon_sa_manager	sa_manager;
 	struct radeon_ib		ibs[RADEON_IB_POOL_SIZE];
 	bool				ready;
···
 	volatile uint32_t		*ptr;
 	u64				gpu_addr;
 };
-
-
-/*
- * Mutex which allows recursive locking from the same process.
- */
-struct radeon_mutex {
-	struct mutex		mutex;
-	struct task_struct	*owner;
-	int			level;
-};
-
-static inline void radeon_mutex_init(struct radeon_mutex *mutex)
-{
-	mutex_init(&mutex->mutex);
-	mutex->owner = NULL;
-	mutex->level = 0;
-}
-
-static inline void radeon_mutex_lock(struct radeon_mutex *mutex)
-{
-	if (mutex_trylock(&mutex->mutex)) {
-		/* The mutex was unlocked before, so it's ours now */
-		mutex->owner = current;
-	} else if (mutex->owner != current) {
-		/* Another process locked the mutex, take it */
-		mutex_lock(&mutex->mutex);
-		mutex->owner = current;
-	}
-	/* Otherwise the mutex was already locked by this process */
-
-	mutex->level++;
-}
-
-static inline void radeon_mutex_unlock(struct radeon_mutex *mutex)
-{
-	if (--mutex->level > 0)
-		return;
-
-	mutex->owner = NULL;
-	mutex_unlock(&mutex->mutex);
-}
 
 
 /*

drivers/gpu/drm/radeon/radeon_device.c

···
 	/* mutex initialization are all done here so we
 	 * can recall function without having locking issues */
 	radeon_mutex_init(&rdev->cs_mutex);
-	mutex_init(&rdev->ib_pool.mutex);
+	radeon_mutex_init(&rdev->ib_pool.mutex);
 	for (i = 0; i < RADEON_NUM_RINGS; ++i)
 		mutex_init(&rdev->ring[i].mutex);
 	mutex_init(&rdev->dc_hw_i2c_mutex);

drivers/gpu/drm/radeon/radeon_ring.c

···
 		return r;
 	}
 
-	mutex_lock(&rdev->ib_pool.mutex);
+	radeon_mutex_lock(&rdev->ib_pool.mutex);
 	idx = rdev->ib_pool.head_id;
 retry:
 	if (cretry > 5) {
 		dev_err(rdev->dev, "failed to get an ib after 5 retry\n");
-		mutex_unlock(&rdev->ib_pool.mutex);
+		radeon_mutex_unlock(&rdev->ib_pool.mutex);
 		radeon_fence_unref(&fence);
 		return -ENOMEM;
 	}
···
 				 */
 				rdev->ib_pool.head_id = (1 + idx);
 				rdev->ib_pool.head_id &= (RADEON_IB_POOL_SIZE - 1);
-				mutex_unlock(&rdev->ib_pool.mutex);
+				radeon_mutex_unlock(&rdev->ib_pool.mutex);
 				return 0;
 			}
 		}
···
 		}
 		idx = (idx + 1) & (RADEON_IB_POOL_SIZE - 1);
 	}
-	mutex_unlock(&rdev->ib_pool.mutex);
+	radeon_mutex_unlock(&rdev->ib_pool.mutex);
 	radeon_fence_unref(&fence);
 	return r;
 }
···
 	if (tmp == NULL) {
 		return;
 	}
-	mutex_lock(&rdev->ib_pool.mutex);
+	radeon_mutex_lock(&rdev->ib_pool.mutex);
 	if (tmp->fence && !tmp->fence->emitted) {
 		radeon_sa_bo_free(rdev, &tmp->sa_bo);
 		radeon_fence_unref(&tmp->fence);
 	}
-	mutex_unlock(&rdev->ib_pool.mutex);
+	radeon_mutex_unlock(&rdev->ib_pool.mutex);
 }
 
 int radeon_ib_schedule(struct radeon_device *rdev, struct radeon_ib *ib)
···
 		return r;
 	}
 
-	mutex_lock(&rdev->ib_pool.mutex);
+	radeon_mutex_lock(&rdev->ib_pool.mutex);
 	if (rdev->ib_pool.ready) {
-		mutex_unlock(&rdev->ib_pool.mutex);
+		radeon_mutex_unlock(&rdev->ib_pool.mutex);
 		radeon_sa_bo_manager_fini(rdev, &tmp);
 		return 0;
 	}
···
 	if (radeon_debugfs_ring_init(rdev)) {
 		DRM_ERROR("Failed to register debugfs file for rings !\n");
 	}
-	mutex_unlock(&rdev->ib_pool.mutex);
+	radeon_mutex_unlock(&rdev->ib_pool.mutex);
 	return 0;
 }
 
···
 {
 	unsigned i;
 
-	mutex_lock(&rdev->ib_pool.mutex);
+	radeon_mutex_lock(&rdev->ib_pool.mutex);
 	if (rdev->ib_pool.ready) {
 		for (i = 0; i < RADEON_IB_POOL_SIZE; i++) {
 			radeon_sa_bo_free(rdev, &rdev->ib_pool.ibs[i].sa_bo);
···
 		radeon_sa_bo_manager_fini(rdev, &rdev->ib_pool.sa_manager);
 		rdev->ib_pool.ready = false;
 	}
-	mutex_unlock(&rdev->ib_pool.mutex);
+	radeon_mutex_unlock(&rdev->ib_pool.mutex);
 }
 
 int radeon_ib_pool_start(struct radeon_device *rdev)