Commit 5ec17c76 authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915/gt: Another tweak for flushing the tasklets 



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: default avatarChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: default avatarMika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201220134858.10510-1-chris@chris-wilson.co.uk
parent 9bb36cf6

drivers/gpu/drm/i915/gt/intel_engine.h

+6 −1
Original line number Diff line number Diff line
@@ -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);

drivers/gpu/drm/i915/gt/intel_engine_cs.c

+5 −5
Original line number Diff line number Diff line
@@ -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);

}



/**

drivers/gpu/drm/i915/i915_request.c

+1 −1
Original line number Diff line number Diff line
@@ -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);