Quoting Chris Wilson (2018-02-01 10:36:20)
> Since commit 7b6da818d86f ("drm/i915: Restore the kernel context after a
> GPU reset on an idle engine") we submit a request following the engine
> reset. The intent is that we don't submit a request if the engine is
> busy (as it will restart active by itself) but we only checked to see if
> there were remaining requests in flight on the hardware and skipped
> checking to see if there were any ready requests that would be
> immediately submitted on restart (the same time as our new request would
> be). Having convinced the engine to appear idle in the previous patch,
> we can use intel_engine_is_idle() as a better test to only submit a new
> request if there are no pending requests.
>
> As it happens, this is tripping up igt/drv_selftest/live_hangcheck in CI
> as we overfill the kernel_context ringbuffer trigger an infinite
> recursion from within the reset.
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104786
> References: 7b6da818d86f ("drm/i915: Restore the kernel context after a GPU
> reset on an idle engine")
> Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
> Cc: Mika Kuoppala <mika.kuopp...@linux.intel.com>
> Cc: Joonas Lahtinen <joonas.lahti...@linux.intel.com>
> Cc: Michel Thierry <michel.thie...@intel.com>
This would be nice to have fixed in CI.
> ---
> drivers/gpu/drm/i915/i915_gem.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 088579324c14..c049496e8757 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -3133,7 +3133,7 @@ void i915_gem_reset(struct drm_i915_private *dev_priv)
> * an incoherent read by the CS (presumably stale TLB). An
> * empty request appears sufficient to paper over the glitch.
> */
> - if (list_empty(&engine->timeline->requests)) {
> + if (intel_engine_is_idle(engine)) {
> struct drm_i915_gem_request *rq;
>
> rq = i915_gem_request_alloc(engine,
> --
> 2.15.1
>
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