[Intel-gfx] [PATCH RFC] drm/i915: Print dmesg warn on unintended hangs

[Chris Wilson]

Quoting Chris Wilson (2017-11-10 12:30:21)
> Quoting Mika Kuoppala (2017-11-10 12:20:55)
> > Chris Wilson <chris at chris-wilson.co.uk> writes:
> > 
> > > Quoting Mika Kuoppala (2017-11-10 11:53:47)
> > >> We have a problem of distinguishing intended hangs
> > >> submitted by igt during CI/bat and hangs that are nonintended
> > >> happening in close proximity.
> > >
> > > Do we? I haven't had that problem in distinguishing them.
> > 
> > Piglit can't tell them apart afaik. Due to info level.
> 
> Piglit? If the test passes, it doesn't matter how the kernel got there,
> the user behaviour is as expected. If the test wants to assert that it
> didn't hang, it can do that.
> 
> I am very opposed to interpreting magic contents within the kernel, more
> so when it is already known by userspace.

A clearer form of identification would be either a context-param saying
that userspace is going to use this context for injecting hang, which we
already have and use, or for fine grained precision having an execbuf
flag (copying onto the request) saying that this is the hanging batch.

But that only makes sense (to me) in the context of gem_reset_stats,
drv_hangman, gem_exec_capture or whichever, where you want such fine
grained checking. And as some point, we acknowledge we are checking
kernel internals (not user behaviour) and move it to the selftests.
-Chris