[Intel-gfx] [PATCH 42/42] drm/i915/gt: Another tweak for flushing the tasklets

[Chris Wilson]

tasklet_kill() ensures that we _yield_ the processor until a remote
tasklet is completed. However, this leads to a starvation condition as
being at the bottom of the scheduler's runqueue means that anything else
is able to run, including all hogs keeping the tasklet occupied.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/gt/intel_engine_cs.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
index e3bda3509cd0..5c08c29e58af 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
@@ -1197,10 +1197,6 @@ void intel_engine_flush_submission(struct intel_engine_cs *engine)
 	if (!t->func)
 		return;
 
-	/* Synchronise and wait for the tasklet on another CPU */
-	tasklet_kill(t);
-
-	/* Having cancelled the tasklet, ensure that is run */
 	local_bh_disable();
 	if (tasklet_trylock(t)) {
 		/* Must wait for any GPU reset in progress. */
@@ -1209,6 +1205,9 @@ void intel_engine_flush_submission(struct intel_engine_cs *engine)
 		tasklet_unlock(t);
 	}
 	local_bh_enable();
+
+	/* Synchronise and wait for the tasklet on another CPU */
+	tasklet_unlock_wait(t);
 }
 
 /**
-- 
2.20.1