1 files changed, 34 insertions, 1 deletions

diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index 8d5a646ebe6a..07e02c4bf5a8 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -151,7 +151,7 @@ static void ttm_bo_release_list(struct kref *list_kref)
         atomic_dec(&bo->glob->bo_count);
         if (bo->resv == &bo->ttm_resv)
                 reservation_object_fini(&bo->ttm_resv);
-
+        mutex_destroy(&bo->wu_mutex);
         if (bo->destroy)
                 bo->destroy(bo);
         else {
@@ -1123,6 +1123,7 @@ int ttm_bo_init(struct ttm_bo_device *bdev,
         INIT_LIST_HEAD(&bo->ddestroy);
         INIT_LIST_HEAD(&bo->swap);
         INIT_LIST_HEAD(&bo->io_reserve_lru);
+        mutex_init(&bo->wu_mutex);
         bo->bdev = bdev;
         bo->glob = bdev->glob;
         bo->type = type;
@@ -1704,3 +1705,35 @@ void ttm_bo_swapout_all(struct ttm_bo_device *bdev)
                 ;
 }
 EXPORT_SYMBOL(ttm_bo_swapout_all);
+
+/**
+ * ttm_bo_wait_unreserved - interruptible wait for a buffer object to become
+ * unreserved
+ *
+ * @bo: Pointer to buffer
+ */
+int ttm_bo_wait_unreserved(struct ttm_buffer_object *bo)
+{
+        int ret;
+
+        /*
+         * In the absense of a wait_unlocked API,
+         * Use the bo::wu_mutex to avoid triggering livelocks due to
+         * concurrent use of this function. Note that this use of
+         * bo::wu_mutex can go away if we change locking order to
+         * mmap_sem -> bo::reserve.
+         */
+        ret = mutex_lock_interruptible(&bo->wu_mutex);
+        if (unlikely(ret != 0))
+                return -ERESTARTSYS;
+        if (!ww_mutex_is_locked(&bo->resv->lock))
+                goto out_unlock;
+        ret = ttm_bo_reserve_nolru(bo, true, false, false, NULL);
+        if (unlikely(ret != 0))
+                goto out_unlock;
+        ww_mutex_unlock(&bo->resv->lock);
+
+out_unlock:
+        mutex_unlock(&bo->wu_mutex);
+        return ret;
+}