[Intel-gfx] [PATCH 2/2] drm/i915/selftests: Exercise resetting in the middle of a wait-on-fence

[Chris Wilson]

Quoting Matthew Auld (2018-07-26 13:26:08)
> On 19 July 2018 at 20:47, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> > On older HW, gen2/3, fence registers are used for detiling GPU commands
> > and as such changing those registers requires serialisation with the
> > requests on the GPU. Anything running on the GPU is subject to a hang,
> > and so we must be able to recover cleanly in the middle of a stuck wait
> > on a fence register.
> >
> > We can simulate using the fence on the GPU simply by marking the fence
> > as active on the request for this vma, the interface being common to all
> > gen, thus broadening the test.
> >
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
> Reviewed-by: Matthew Auld <matthew.auld at intel.com>

Ta, this test has proven itself quite useful at picking out some of the
nasty deadlocks in trying to make reset BKLless.
-Chris