[Intel-gfx] [PATCH] drm/i915: Revert i915.semaphore=1 default from 47ae63e0

[Eric Anholt]

On Thu, 19 May 2011 16:50:00 -0400, Andrew Lutomirski <luto at mit.edu> wrote:
> On Thu, May 19, 2011 at 3:56 PM, Keith Packard <keithp at keithp.com> wrote:
> > On Fri, 13 May 2011 12:14:54 -0400, Andy Lutomirski <luto at MIT.EDU> wrote:
> >
> >> My Q67 / i7-2600 box has rev09 Sandy Bridge graphics.  It hangs
> >> instantly when GNOME loads and it hangs so hard the reset button
> >> doesn't work.  Setting i915.semaphore=0 fixes it.
> >
> > Can you describe precisely what hardware you have? The make and model of
> > the motherboard and the exact model of CPU? I'd like to get this issue
> > resolved for 2.6.40 and need to have a reliable way to reproduce the
> > hang; replicating your hardware may be a good way of doing that.
> 
> Intel DQ67SW.  AMT is enabled but the port 5900 is closed (because I
> can't figure out how to turn on the kvm).
> 
> The system boots from UEFI (which is buggy, both because efifb doesn't
> recognize my hardware, because asking the firmware for the boot menu
> causes all efivars entries to be ignored, and because unless I set
> reboot=k the system crashes on reboot).
> 
> Userspace is F15 running compiz (*not* gnome-shell).
> 
> BIOS is SWQ6710H.86A.0051.2011.0413.1154.
> 
> CPU is:
> processor       : 0
> vendor_id       : GenuineIntel
> cpu family      : 6
> model           : 42
> model name      : Intel(R) Core(TM) i7-2600 CPU @ 3.40GHz
> stepping        : 7

I fear this bug is just "getting more asynchronous with the GPU means we
trigger race conditions on the GPU more easily."  On that note, could
you retest with Mesa as of this commit, since I'm told this is a GT1 CPU:

commit ef59049c5242a1be7fa59a182d342191185dd62b
Author: Eric Anholt <eric at anholt.net>
Date:   Sun Jun 5 23:20:57 2011 -0700

    i965: Fix flipped GT1 vs GT2 URB VS entry count limits.
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