[CI] drm/i915/gt: Another tweak for flushing the tasklets

Commit Message

Chris Wilson Dec. 20, 2020, 1:48 p.m. UTC

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 <[e-mail]>
Reviewed-by: Mika Kuoppala <[e-mail]>
---
 drivers/gpu/drm/i915/gt/intel_engine.h    |  7 ++++++-
 drivers/gpu/drm/i915/gt/intel_engine_cs.c | 10 +++++-----
 drivers/gpu/drm/i915/i915_request.c       |  2 +-
 3 files changed, 12 insertions(+), 7 deletions(-)

Patch

diff --git a/drivers/gpu/drm/i915/gt/intel_engine.h b/drivers/gpu/drm/i915/gt/intel_engine.h
index 6606b1dbf3d6..47ee8578e511 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine.h
+++ b/drivers/gpu/drm/i915/gt/intel_engine.h
@@ -232,7 +232,12 @@  static inline void __intel_engine_reset(struct intel_engine_cs *engine,
 
 bool intel_engines_are_idle(struct intel_gt *gt);
 bool intel_engine_is_idle(struct intel_engine_cs *engine);
-void intel_engine_flush_submission(struct intel_engine_cs *engine);
+
+void __intel_engine_flush_submission(struct intel_engine_cs *engine, bool sync);
+static inline void intel_engine_flush_submission(struct intel_engine_cs *engine)
+{
+	__intel_engine_flush_submission(engine, true);
+}
 
 void intel_engines_reset_default_submission(struct intel_gt *gt);
 
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
index 97ceaf7116e8..bb1c1adad78a 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
@@ -1190,17 +1190,13 @@  static bool ring_is_idle(struct intel_engine_cs *engine)
 	return idle;
 }
 
-void intel_engine_flush_submission(struct intel_engine_cs *engine)
+void __intel_engine_flush_submission(struct intel_engine_cs *engine, bool sync)
 {
 	struct tasklet_struct *t = &engine->execlists.tasklet;
 
 	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 +1205,10 @@  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 */
+	if (sync)
+		tasklet_unlock_wait(t);
 }
 
 /**
diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index 2675c6d70779..45744c3ef7c4 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -1825,7 +1825,7 @@  long i915_request_wait(struct i915_request *rq,
 	 * for unhappy HW.
 	 */
 	if (i915_request_is_ready(rq))
-		intel_engine_flush_submission(rq->engine);
+		__intel_engine_flush_submission(rq->engine, false);
 
 	for (;;) {
 		set_current_state(state);