From ecebca79f6976ddaddfd054d699272515869ea28 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Mon, 29 Aug 2016 19:16:13 +0100 Subject: [PATCH] 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 Cc: Sumit Semwal Cc: Gustavo Padovan Cc: linux-media@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Cc: linaro-mm-sig@lists.linaro.org Reviewed-by: Gustavo Padovan Signed-off-by: Sumit Semwal Link: http://patchwork.freedesktop.org/patch/msgid/20160829181613.30722-1-chris@chris-wilson.co.uk --- drivers/dma-buf/sync_file.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/dma-buf/sync_file.c b/drivers/dma-buf/sync_file.c index 486d29c1a830..abb5fdab75fd 100644 --- a/drivers/dma-buf/sync_file.c +++ b/drivers/dma-buf/sync_file.c @@ -306,7 +306,8 @@ static unsigned int sync_file_poll(struct file *file, poll_table *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, fence_check_cb_func) < 0) wake_up_all(&sync_file->wq); -- 2.20.1