[Bug 94930] Freeze during activation of external display on Lenovo X260

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=94930

--- Comment #3 from Dennis Wassenberg <dennis.wassenberg at secunet.com> ---
I got a Lenovo X260 with Intel i7-6600U. There everything is fine. No freeze
will occur. So it looks like that this issue will happen with i7-6500U CPUs
only. I assume that the CPU or GPU are not the root cause because the GPUs are
the same. The CPUs differ mostly in clock speeds. Additionally the i7-6600U CPU
supports AMT.

So maybe it is a race condition inside the i915 code which appears at i7-6500U
CPU only because of the different clock speeds?!?

I did some additional checks:

I reverted the commit 4e0963c7663b0538b5a21fb49d17ea4ad64de861 in that way that
I removed the union and use the 2 structs instead (like before this commit).
Still freezing...

Because the patch affects wakermarking I applied the following patch:
https://patchwork.freedesktop.org/patch/69417/
to enable the possibility to disable wartermarking for debugging purposes.
After disable watermarking, it is still freezing... This confirms the
assumption that it might be a race condition.

Any ideas?

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