Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1455759

Re: [PATCH v4 5/5] dma-buf/sync_file: only enable fence signalling on poll()

Show all headers | View raw

On Tue, Jul 12, 2016 at 03:08:45PM -0300, Gustavo Padovan wrote:
> From: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
> 
> Signalling doesn't need to be enabled at sync_file creation, it is only
> required if userspace waiting the fence to signal through poll().
> 
> Thus we delay fence_add_callback() until poll is called. It only adds the
> callback the first time poll() is called. This avoid re-adding the same
> callback multiple times.
> 
> v2: rebase and update to work with new fence support for sync_file
> 
> v3: use atomic operation to set enabled and protect fence_add_callback()

There's actually a spare bit in fence->flags you can use for this.

#define POLL_ENABLED FENCE_FLAG_USER_BITS

if (test_bit(POLL_ENABLED, &sync_file->fence->flags))
	fence_remove_callback(sync_file->fence, &sync_file->cb);

...

if (!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);
}

Saves adding a raw atomic.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre

Back to linux.kernel | Previous | Next — Next in thread | Find similar | Unroll thread

Thread

Re: [PATCH v4 5/5] dma-buf/sync_file: only enable fence signalling  on poll() Chris Wilson <chris@chris-wilson.co.uk> - 2016-08-03 13:50 +0200
  Re: [PATCH v4 5/5] dma-buf/sync_file: only enable fence signalling  on poll() Gustavo Padovan <gustavo@padovan.org> - 2016-08-04 23:20 +0200
    Re: [PATCH v4 5/5] dma-buf/sync_file: only enable fence signalling  on poll() Chris Wilson <chris@chris-wilson.co.uk> - 2016-08-04 23:40 +0200

csiph-web