drm/radeon: fix vm deadlocks on cayman

Locking mutex in different orders just screams for
deadlocks, and some testing showed that it is actually
quite easy to trigger them.
Signed-off-by: Christian König <deathsimple@vodafone.de>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/radeon_gart.c

@@ -475,14 +475,20 @@ int radeon_vm_bo_add(struct radeon_device *rdev,
 	}
 
 	mutex_lock(&vm->mutex);
+	if (last_pfn > vm->last_pfn) {
+		/* release mutex and lock in right order */
+		mutex_unlock(&vm->mutex);
+		radeon_mutex_lock(&rdev->cs_mutex);
+		mutex_lock(&vm->mutex);
+		/* and check again */
 		if (last_pfn > vm->last_pfn) {
 			/* grow va space 32M by 32M */
 			unsigned align = ((32 << 20) >> 12) - 1;
-		radeon_mutex_lock(&rdev->cs_mutex);
 			radeon_vm_unbind_locked(rdev, vm);
-		radeon_mutex_unlock(&rdev->cs_mutex);
 			vm->last_pfn = (last_pfn + align) & ~align;
 		}
+		radeon_mutex_unlock(&rdev->cs_mutex);
+	}
 	head = &vm->va;
 	last_offset = 0;
 	list_for_each_entry(tmp, &vm->va, vm_list) {
@@ -595,8 +601,8 @@ int radeon_vm_bo_rmv(struct radeon_device *rdev,
 	if (bo_va == NULL)
 		return 0;
 
-	mutex_lock(&vm->mutex);
 	radeon_mutex_lock(&rdev->cs_mutex);
+	mutex_lock(&vm->mutex);
 	radeon_vm_bo_update_pte(rdev, vm, bo, NULL);
 	radeon_mutex_unlock(&rdev->cs_mutex);
 	list_del(&bo_va->vm_list);
@@ -641,9 +647,8 @@ void radeon_vm_fini(struct radeon_device *rdev, struct radeon_vm *vm)
 	struct radeon_bo_va *bo_va, *tmp;
 	int r;
 
-	mutex_lock(&vm->mutex);
-
 	radeon_mutex_lock(&rdev->cs_mutex);
+	mutex_lock(&vm->mutex);
 	radeon_vm_unbind_locked(rdev, vm);
 	radeon_mutex_unlock(&rdev->cs_mutex);