[PATCH 4/4] drm/i915/selftests: Set preemption timeout to zero in cancel reset test

[Matthew Brost <matthew.brost@intel.com>]

Set the preemption timeout to zero to prove that request cancellation
with preemption disabled works. Also this seals a race between a
possible preemption and request cancellation.

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
---
 drivers/gpu/drm/i915/selftests/i915_request.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/selftests/i915_request.c b/drivers/gpu/drm/i915/selftests/i915_request.c
index 2a99dd7c2fe8a..e522e24129f9b 100644
--- a/drivers/gpu/drm/i915/selftests/i915_request.c
+++ b/drivers/gpu/drm/i915/selftests/i915_request.c
@@ -790,8 +790,9 @@ static int __cancel_completed(struct intel_engine_cs *engine)
  * wait for spinner to start, create a NOP request and submit it, cancel the
  * spinner, wait for spinner to complete and verify it failed with an error,
  * finally wait for NOP request to complete verify it succeeded without an
- * error. Preemption timeout also reduced / restored so test runs in a timely
- * maner.
+ * error. Preemption timeout also set to zero to ensure cancellation works with
+ * preemption disabled and to ensure the NOP request doesn't trigger a
+ * preemption on the spinner sealing a race between a preemption and the cancel.
  */
 static int __cancel_reset(struct drm_i915_private *i915,
 			  struct intel_engine_cs *engine)
@@ -807,7 +808,7 @@ static int __cancel_reset(struct drm_i915_private *i915,
 		return 0;
 
 	preempt_timeout_ms = engine->props.preempt_timeout_ms;
-	engine->props.preempt_timeout_ms = 100;
+	engine->props.preempt_timeout_ms = 0;
 
 	if (igt_spinner_init(&spin, engine->gt))
 		goto out_restore;
-- 
2.34.1