Latest Xorg from git breaks Mesa with VDPAU playback.

[Boris]

I am using the latest Xorg, Mesa from git and the Linux 4.7.2 kernel. I 
have an Nvdia NVA8 chipset[ion] with xorg setup to use the latest 
nouveau driver and it also supposed vdpau and I have the firmware 
required to get video acceleration. When attempting to playback video 
with mplayer using vdpau, I noticed the video playback freezes after a 
few frames when trying to playing video using vdpau. The system doesn't 
freezes but just the video cannot seem to continue playing since the 
video playback. I tried different kernels and Mesa versions and it 
didn't make any issue. When I attempt to recompile Xorg from git, I 
found the following commit on 2016-07-21 breaks the vdpau playback for me.

https://cgit.freedesktop.org/xorg/xserver/commit/?id=f993091e7db81b0420e23c485378cba112278839

Commit:    f993091e7db81b0420e23c485378cba112278839
os: Switch server to poll(2) [v3]
Eliminates all of the fd_set mangling in the server main thread

v2: Listen for POLLOUT while writes are blocked.

v3: Only mark client not ready on EAGAIN return from read

Signed-off-by: Keith Packard <keithp at keithp.com>
Reviewed-by: Adam Jackson <ajax at redhat.com>


Anyone else experience this issue? It seems if I compile with the 
previous commit [8f1edf4bd3a1f050ce9eeb5eac45dd1a8f7a6d5e], everything 
works perfectly.