vmwgfx: Allow reference and unreference of NULL fence objects.

The execbuf utils may call reference on NULL fence objects.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Jakob Bornecrantz <jakob@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c b/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c
index 5065a14..5f60be7 100644 (file)
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c
@@ -177,6 +177,9 @@ out_unlock:
 
 struct vmw_fence_obj *vmw_fence_obj_reference(struct vmw_fence_obj *fence)
 {
+       if (unlikely(fence == NULL))
+               return NULL;
+
        kref_get(&fence->kref);
        return fence;
 }
@@ -191,8 +194,12 @@ struct vmw_fence_obj *vmw_fence_obj_reference(struct vmw_fence_obj *fence)
 void vmw_fence_obj_unreference(struct vmw_fence_obj **fence_p)
 {
        struct vmw_fence_obj *fence = *fence_p;
-       struct vmw_fence_manager *fman = fence->fman;
+       struct vmw_fence_manager *fman;
+
+       if (unlikely(fence == NULL))
+               return;
 
+       fman = fence->fman;
        *fence_p = NULL;
        spin_lock_irq(&fman->lock);
        BUG_ON(atomic_read(&fence->kref.refcount) == 0);