Since last week I have random freezes with the amdgpu driver (running on
Kaveri).

Once the issue occurs the display freezes. It's not fixable by switch to VT2
and back.

In Xorg.0.log I can find multiple times:
[ 92357.021] (WW) AMDGPU(0): flip queue failed: Device or resource busy
[ 92357.021] (WW) AMDGPU(0): Page flip failed: Device or resource busy
[ 92357.021] (EE) AMDGPU(0): present flip failed

No related messages in the journal or dmesg afaics.

It does not seem to be related to a specific event (like a video playing), but
just happens out of nowhere.
I didn't find a way to reproduce it specifically.

Possibly related packages that I built in that time:
* dev-lang/llvm-scm::arbor 2016-06-11 07:42:19 UTC
* dev-lang/llvm-scm::arbor 2016-06-19 07:29:42 UTC
* x11-dri/mesa-12.0.0-rc4::x11 2016-06-21 21:40:48 UTC
* dev-lang/llvm-scm::arbor 2016-07-02 11:57:34 UTC
* dev-lang/clang-scm::arbor 2016-07-02 12:43:00 UTC
* dev-lang/llvm-3.8.0-r1::arbor 2016-07-12 20:04:14 UTC
* dev-lang/clang-3.8.0::arbor 2016-07-12 20:48:27 UTC
* x11-dri/mesa-12.0.0::x11 2016-07-13 04:42:47 UTC
* x11-dri/mesa-12.0.1::x11 2016-07-17 14:25:44 UTC
* x11-server/xorg-server-1.18.4::x11 2016-07-20 16:06:18 UTC

I couldn't get mesa 12 to built with llvm-scm anymore, so I downgraded.
Still, I doubt it's related.

It's hard to be certain about this, but it could have been a regressing coming
with mesa 12 and possibly mesa-12.0.0.
I'm pretty sure I haven't seen the freeze before 12.0.0 final, but it's hard to
be certain about this with an issue so random.

In case it matters, my xorg settings are: 
Section "Device"
    Identifier  "AMDGPU"
    Driver      "amdgpu"
    Option      "TearFree" "Off"
    Option      "EnablePageFlip" "On"
    Option      "DRI" "3"
EndSection

IIRC, this is now standard, so nothing special here.