[Bug 108820] [SKL] GPU hangs in benchmarks using compute shaders with drm-tip v4.20-rc kernels

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=108820

--- Comment #12 from Jakub Okoński <jakub at okonski.org> ---
OK, I think I found the precise issue. It occurs when using a control flow
barrier in the shader with more than 64 items in the workgroup.

To put in concrete terms:

Shader A:
...
layout (local_size_x = 64) in;
void main() {
    // code
    barrier();
}

----
Works fine.

Shader B:
...
layout (local_size_x = 65) in;
void main() {
    // code
    barrier();
}

----
Hangs with INTEL-MESA: error: src/intel/vulkan/anv_device.c:2091: GPU hung on
one of our command buffers (VK_ERROR_DEVICE_LOST).


Shader C:
...
layout (local_size_x = 65) in;
void main() {
    // code
    // barrier(); without any control flow barriers inside
}
----
Works fine as well.

This should be enough to zoom into the issue, but if you need code you can
execute and repro locally, let me know and I can deliver it.

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