dma-buf: avoid scheduling on fence status query v2

When a timeout of zero is specified, the caller is only interested in
the fence status.

In the current implementation, dma_fence_default_wait will always call
schedule_timeout() at least once for an unsignaled fence. This adds a
significant overhead to a fence status query.

Avoid this overhead by returning early if a zero timeout is specified.

v2: move early return after enable_signaling

Signed-off-by: Andres Rodriguez <andresx7@gmail.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170426144620.3560-1-andresx7@gmail.com

diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
index 0918d3f003d65d633a6e06a2c8d41a47fc42f9b5..57da14c15987fc019d1786ec0a4b0bd65077cf99 100644 (file)
--- a/drivers/dma-buf/dma-fence.c
+++ b/drivers/dma-buf/dma-fence.c
@@ -402,6 +402,11 @@ dma_fence_default_wait(struct dma_fence *fence, bool intr, signed long timeout)
                }
        }
 
+       if (!timeout) {
+               ret = 0;
+               goto out;
+       }
+
        cb.base.func = dma_fence_default_wait_cb;
        cb.task = current;
        list_add(&cb.base.node, &fence->cb_list);