[Bug 54226] [snb 3.5] stale semaphore sync seqno (typically as seen on bcs->rcs)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=54226

--- Comment #226 from Chris Wilson <chris at chris-wilson.co.uk> ---
(In reply to Martin Steigerwald from comment #225)
> Chris, you referred me to this bug as I reported
> 
> Bug 90835 - [4.1-rc6] gpu hang: ecode 6:-1:0x00000000, Kicking stuck
> semaphore on render ring
> 
> I skimmed through it and it appears that there are some patches to test? But
> I am not sure which ones these are. Can you or someone else enlighten me?

There's likely a modest improvement in 4.2.

> Also I note that I still use
> 
>         Option          "AccelMethod"   "uxa"
> 
> and I have
> 
> martin at merkaba:~> cat /etc/modprobe.d/i915-kms.conf 
> options i915 modeset=1 i915_enable_rc6=7

Fortuitously that dangerous option doesn't do anything for your kernel.

> ffffffff813a4b0e
> thus maximum energy saving. But according to powertop it never enters the
> highest sleep state anyway.
> 
> I will remove the AccelMethod setting now and see whether it helps. If not,
> I downgrade to 4.1-rc4 for now, as issues have been at least much less
> frequent with it.

Purely circumstantial.

> And its really that for me 4.1-rc6 makes things much *worse*. I am typing
> this after a clean reboot and already got the GPU hang again. It happens
> about every few minutes. Are you really sure this is the same GPU hang? I
> didn´t have this before 4.1 kernel?

Yes.

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