dma-buf/sync-file: Avoid enable fence signaling if poll(.timeout=0)

If we being polled with a timeout of zero, a nonblocking busy query,
we don't need to install any fence callbacks as we will not be waiting.
As we only install the callback once, the overhead comes from the atomic
bit test that also causes serialisation between threads.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Gustavo Padovan <gustavo@padovan.org>
Cc: linux-media@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Cc: linaro-mm-sig@lists.linaro.org
Reviewed-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20160829181613.30722-1-chris@chris-wilson.co.uk
This commit is contained in:
Chris Wilson 2016-08-29 19:16:13 +01:00 коммит произвёл Sumit Semwal
Родитель f6ce410a59
Коммит ecebca79f6
1 изменённых файлов: 2 добавлений и 1 удалений

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@ -306,7 +306,8 @@ static unsigned int sync_file_poll(struct file *file, poll_table *wait)
poll_wait(file, &sync_file->wq, wait); poll_wait(file, &sync_file->wq, wait);
if (!test_and_set_bit(POLL_ENABLED, &sync_file->fence->flags)) { if (!poll_does_not_wait(wait) &&
!test_and_set_bit(POLL_ENABLED, &sync_file->fence->flags)) {
if (fence_add_callback(sync_file->fence, &sync_file->cb, if (fence_add_callback(sync_file->fence, &sync_file->cb,
fence_check_cb_func) < 0) fence_check_cb_func) < 0)
wake_up_all(&sync_file->wq); wake_up_all(&sync_file->wq);