[Intel-gfx] [REGRESSION] system hang on ILK/SNB/IVB

[Lukas Wunner]

Hi Tomi,

On Thu, Mar 31, 2016 at 10:21:16AM +0300, Tomi Sarvela wrote:
> The problem with the results in your link is that there is no HSW, ILK, IVB
> or SNB results. This might give the impression that everything is well.
> 
> Most damning is lack of HSW-gt2 and SNB-dellxps: those machines hang on to
> APC, and have run quite stably for every Patchwork run. The case isn't strong
> enough yet that series should fail if either of those won't run, but it might
> be so in future.

So my patch seeking to fix the hangs has passed Romania CI with "success":
https://patchwork.freedesktop.org/series/5125/

However I don't see HSW-gt2 and SNB-dellxps in their hardware lineup.
And I would still like to know what the actual cause of the hangs is
since they do not occur on my IVB laptop.

If you get the chance maybe you can repeat the test and include a
"dump_stack();" at the beginning of intel_fbdev_output_poll_changed()
and intel_fbdev_restore_mode(). This should show in the logs which of
the two functions is called during suspend/resume and from where it's
called. My guess is that this particular hardware causes a hotplug
signal to be generated upon waking up. If the hangs do not stop with
this patch, booting with "no_console_suspend" should at least show
what's going on.

Thank you & best regards,

Lukas