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

[Gustavo Padovan <gustavo@padovan.org>]

2016-08-03 Chris Wilson <chris@chris-wilson.co.uk>:

> 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

Wouldn't it be better to add a new bit to fence_flags_bit?

	Gustavo