[Bug 84744] [sna] X-Server freeze when playing a video using VA-API in dual-head configuration

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=84744

--- Comment #11 from M. G. <gentoo at gishpuppy.com> ---
(In reply to Chris Wilson from comment #10)
> (In reply to M. G. from comment #8)
> > Unfortunately I have no /proc/`pidof Xorg`/stack file. Can you tell me how
> > to enable it? I have set CONFIG_STACKTRACE_SUPPORT=y in my kernel config.
> 
> Perhaps your process is called X, not Xorg. You can take a look at "ps ax"
> and manually grab the pid to use above.

OK, I figured out why the file was missing. I had to recompile my kernel with
Kernel hacking/Kernel debugging and Kernel hacking/Tracers enabled.

> > After uploading the above files with my second PC, I switched the monitor
> > input back and saw that the video moved on a few frames but the video was
> > still stuck. After moving the mouse the video playback continued fine. I
> > will attach the syslog. Does this help?
> 
> Indeed. That sort of ties in with it not appearing to freeze inside the
> graphics driver... Could you try finding the right /proc/<pid>/stack and/or
> attaching gdb and getting a backtrace?

Here is the stacktrace output:

[<ffffffff813a20b2>] drm_read+0x162/0x1c0
[<ffffffff811481fb>] vfs_read+0x9b/0x190
[<ffffffff8114849a>] SyS_read+0x4a/0xc0
[<ffffffff815cd812>] system_call_fastpath+0x16/0x1b
[<ffffffffffffffff>] 0xffffffffffffffff

I haven't used gdb before. If you need a backtrace it might take a while
because I first have to find out what to do in order to get a backtrace.

> Time to read syslog...

I think this is the relevant part:

[  234.782295] [drm:drm_calc_vbltimestamp_from_scanoutpos], crtc 0 : v 7
p(0,-34)@ 234.770961 -> 234.771420 [e 0 us, 0 rep]
[  234.795367] [drm:vblank_disable_fn], disabling vblank on crtc 0
[  234.795383] [drm:drm_calc_vbltimestamp_from_scanoutpos], crtc 0 : v 5
p(0,935)@ 234.784052 -> 234.771424 [e 0 us, 0 rep]
[  270.745528] [drm:drm_ioctl], pid=1841, dev=0xe200, auth=1, I915_GEM_BUSY
[  270.745571] [drm:drm_ioctl], pid=1841, dev=0xe200, auth=1, I915_GEM_BUSY
[  270.745591] [drm:drm_ioctl], pid=1841, dev=0xe200, auth=1, I915_GEM_BUSY
[  270.745800] [drm:drm_ioctl], pid=1841, dev=0xe200, auth=1, I915_GEM_THROTTLE
[  270.746352] [drm:drm_ioctl], pid=1841, dev=0xe200, auth=1,
DRM_IOCTL_WAIT_VBLANK
[  270.746362] [drm:drm_vblank_get], enabling vblank on crtc 0, ret: 0          
[  270.746375] [drm:drm_calc_vbltimestamp_from_scanoutpos], crtc 0 : v 5
p(0,1183)@ 270.734067 -> 270.718089 [e 0 us, 0 rep]                             
[  270.746389] [drm:drm_update_vblank_count], enabling vblank interrupts on
crtc 0, missed 2155                                                             
[  270.746398] [drm:drm_wait_vblank], waiting on vblank count 16134, crtc 0     
[  270.746401] [drm:drm_wait_vblank], returning 16134 to client

Maybe some vblank issue?

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