[Intel-gfx] [PATCH igt 3/9] igt/drv_hangman: Inject a true hang

[Ville Syrjälä]

On Wed, Dec 16, 2015 at 10:37:55AM +0000, Chris Wilson wrote:
> On Wed, Dec 16, 2015 at 10:02:27AM +0100, Daniel Vetter wrote:
> > On Sat, Dec 12, 2015 at 08:02:49PM +0000, Chris Wilson wrote:
> > > Wean drv_hangman off the atrocious stop_rings and use a real GPU hang
> > > instead.
> > > 
> > > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > 
> > Doesn't this kill pre-gen6? Or at least anything where we don't have
> > proper hang recovery ... Lack of that is why I've done the original
> > stop_rings fun.
> 
> Originally, igt_hang_ring required gen >= 5, but since that Ville has
> been working hard on getting reset support working for gen3 and gen4,
> now we query the kernel as to whether it can reset the device. So by
> switching over we lose testing of simulated hangs and recovery code (or 
> KMS handling during wedged) for gen2.
> 
> It is a loss in test coverage, but the benefit is that we can remove the
> hang injection code from the kernel. And that is a tradeoff I am willing
> to make.

One day I will get around to trying D3 as a reset mechanism for gen2 ;)
Until then, losing the gen2 test coverage seems fairly reasonable.
I suppose the only thing it's really testing on gen2 is making sure we
don't lock up or oops when the gpu hangs.

So what might be nice is a way to force the hang tests to run even 
when gpu reset isn't supported, just to make sure the system doesn't
die completely. Obviously it's going to be slow to run such tests due
to needing a reboot between every test, but it would be enough to do
an occasional spot check to see if there's been a regression.

-- 
Ville Syrjälä
Intel OTC