[PATCH] drm/i915/gt: Restart the heartbeat timer when forcing a pulse

[John.C.Harrison at Intel.com]

From: John Harrison <John.C.Harrison at Intel.com>

The context persistence code does things like send super high priority
heartbeat pulses to ensure any leaked context can still be pre-empted
and thus isn't a total denial of service but only a minor denial of
service. Unfortunately, it wasn't bothering to restart the heatbeat
worker with a fresh timeout. Thus, if a persistent context happened to
be closed just before the heartbeat was going to go ping anyway then
the forced pulse would get a negligble execution time. And as the
forced pulse is super high priority, the worker thread's next step is
a reset. Which means a potentially innocent system randomly goes boom
when attempting to close a context. So, force a re-schedule of the
worker thread with the appropriate timeout.

Signed-off-by: John Harrison <John.C.Harrison at Intel.com>
---
 drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c b/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
index 1a8e2b7db0138..4ae2fa0b61dd4 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
@@ -290,6 +290,9 @@ static int __intel_engine_pulse(struct intel_engine_cs *engine)
 	heartbeat_commit(rq, &attr);
 	GEM_BUG_ON(rq->sched.attr.priority < I915_PRIORITY_BARRIER);
 
+	/* Ensure the forced pulse gets a full period to execute */
+	next_heartbeat(engine);
+
 	return 0;
 }
 
-- 
2.43.0