In order to test how fast the heartbeat can respond, we measure with the
interval set to its minimum. Before we measure though, we want to be
sure we start with a fresh pulse, and so wait until any old one is
complete. During that wait though, we were continually flushing the
work, and so continually re-evaluating to see if the pulse was complete,
and each attempt would count as an unresponsive system. If the engine
did not complete the request in the couple of busy-spins, it would flag
an error. This is unfortunate, so let's not busy-spin waiting for the
old heartbeat, but terminate it and start afresh.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
.../gpu/drm/i915/gt/selftest_engine_heartbeat.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/selftest_engine_heartbeat.c b/drivers/gpu/drm/i915/gt/selftest_engine_heartbeat.c
index e73854dd2fe0..d64ea0b4b493 100644
--- a/drivers/gpu/drm/i915/gt/selftest_engine_heartbeat.c
+++ b/drivers/gpu/drm/i915/gt/selftest_engine_heartbeat.c
@@ -210,17 +210,15 @@ static int __live_heartbeat_fast(struct intel_engine_cs *engine)
intel_engine_pm_get(engine);
- err = intel_engine_set_heartbeat(engine, 1);
- if (err)
- goto err_pm;
-
for (i = 0; i < ARRAY_SIZE(times); i++) {
- /* Manufacture a tick */
do {
- while (READ_ONCE(engine->heartbeat.systole))
- flush_delayed_work(&engine->heartbeat.work);
+ /* Manufacture a tick */
+ intel_engine_park_heartbeat(engine);
+ engine->serial++; /* pretend we are not idle! */
+ err = intel_engine_set_heartbeat(engine, 1);
+ if (err)
+ goto err_pm;
- engine->serial++; /* quick, pretend we are not idle! */
flush_delayed_work(&engine->heartbeat.work);
if (!delayed_work_pending(&engine->heartbeat.work)) {
pr_err("%s: heartbeat did not start\n",
--
2.20.1
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