[PATCH 022/262] drm/i915/preemption: Select timeout when scheduling

[Chris Wilson <chris@chris-wilson.co.uk>]

The choice of preemption timeout is determined by the context from which
we trigger the preemption, as such allow the caller to specify the
desired timeout.

Effectively the other choice would be to use the shortest timeout along
the dependency chain. However, given that we would have already
triggered preemption for the dependency chain, we can assume that no
preemption along that chain is more important than the current request,
ergo we need only consider the current timeout. Realising this, we can
then pass control of the preemption timeout to the caller for greater
flexibility.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_gem.c            |   2 +-
 drivers/gpu/drm/i915/i915_request.c        |   2 +-
 drivers/gpu/drm/i915/intel_lrc.c           |   5 +-
 drivers/gpu/drm/i915/intel_ringbuffer.h    |   6 +-
 drivers/gpu/drm/i915/selftests/intel_lrc.c | 110 ++++++++++++++++++++-
 5 files changed, 118 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index fa09837d0569..0ec4c7a7c237 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -581,7 +581,7 @@ static void __fence_set_priority(struct dma_fence *fence,
 	local_bh_disable();
 	rcu_read_lock(); /* RCU serialisation for set-wedged protection */
 	if (engine->schedule)
-		engine->schedule(rq, attr);
+		engine->schedule(rq, attr, 0);
 	rcu_read_unlock();
 	local_bh_enable(); /* kick the tasklets if queues were reprioritised */
 }
diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index fc499bcbd105..c3893312cb9d 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -1113,7 +1113,7 @@ void __i915_request_add(struct i915_request *request, bool flush_caches)
 	local_bh_disable();
 	rcu_read_lock(); /* RCU serialisation for set-wedged protection */
 	if (engine->schedule)
-		engine->schedule(request, &request->gem_context->sched);
+		engine->schedule(request, &request->gem_context->sched, 0);
 	rcu_read_unlock();
 	i915_sw_fence_commit(&request->submit);
 	local_bh_enable(); /* Kick the execlists tasklet if just scheduled */
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index b6f369d06bb8..c5795b9944b1 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -1290,7 +1290,8 @@ sched_lock_engine(struct i915_sched_node *node, struct intel_engine_cs *locked)
 }
 
 static void execlists_schedule(struct i915_request *request,
-			       const struct i915_sched_attr *attr)
+			       const struct i915_sched_attr *attr,
+			       unsigned int timeout)
 {
 	struct i915_priolist *uninitialized_var(pl);
 	struct intel_engine_cs *engine, *last;
@@ -1393,7 +1394,7 @@ static void execlists_schedule(struct i915_request *request,
 
 		if (prio > engine->execlists.queue_priority &&
 		    i915_sw_fence_done(&sched_to_request(node)->submit)) {
-			__update_queue(engine, prio, 0);
+			__update_queue(engine, prio, timeout);
 			tasklet_hi_schedule(&engine->execlists.tasklet);
 		}
 	}
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 495cc2628fa9..769ac73004c4 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -478,14 +478,16 @@ struct intel_engine_cs {
 	 */
 	void		(*submit_request)(struct i915_request *rq);
 
-	/* Call when the priority on a request has changed and it and its
+	/*
+	 * Call when the priority on a request has changed and it and its
 	 * dependencies may need rescheduling. Note the request itself may
 	 * not be ready to run!
 	 *
 	 * Called under the struct_mutex.
 	 */
 	void		(*schedule)(struct i915_request *request,
-				    const struct i915_sched_attr *attr);
+				    const struct i915_sched_attr *attr,
+				    unsigned int timeout);
 
 	/*
 	 * Cancel all requests on the hardware, or queued for execution.
diff --git a/drivers/gpu/drm/i915/selftests/intel_lrc.c b/drivers/gpu/drm/i915/selftests/intel_lrc.c
index 40c1f6951444..7efa52e514ab 100644
--- a/drivers/gpu/drm/i915/selftests/intel_lrc.c
+++ b/drivers/gpu/drm/i915/selftests/intel_lrc.c
@@ -406,7 +406,7 @@ static int live_late_preempt(void *arg)
 		}
 
 		attr.priority = I915_PRIORITY_MAX;
-		engine->schedule(rq, &attr);
+		engine->schedule(rq, &attr, 0);
 
 		if (!wait_for_spinner(&spin_hi, rq)) {
 			pr_err("High priority context failed to preempt the low priority context\n");
@@ -618,6 +618,113 @@ static int live_preempt_reset(void *arg)
 	return err;
 }
 
+static int live_late_preempt_timeout(void *arg)
+{
+	struct drm_i915_private *i915 = arg;
+	struct i915_gem_context *ctx_hi, *ctx_lo;
+	struct spinner spin_hi, spin_lo;
+	struct intel_engine_cs *engine;
+	enum intel_engine_id id;
+	int err = -ENOMEM;
+
+	if (!HAS_LOGICAL_RING_PREEMPTION(i915))
+		return 0;
+
+	mutex_lock(&i915->drm.struct_mutex);
+
+	if (spinner_init(&spin_hi, i915))
+		goto err_unlock;
+
+	if (spinner_init(&spin_lo, i915))
+		goto err_spin_hi;
+
+	ctx_hi = kernel_context(i915);
+	if (!ctx_hi)
+		goto err_spin_lo;
+
+	ctx_lo = kernel_context(i915);
+	if (!ctx_lo)
+		goto err_ctx_hi;
+
+	for_each_engine(engine, i915, id) {
+		struct i915_request *rq;
+
+		rq = spinner_create_request(&spin_lo, ctx_lo, engine, MI_NOOP);
+		if (IS_ERR(rq)) {
+			err = PTR_ERR(rq);
+			goto err_ctx_lo;
+		}
+
+		i915_request_add(rq);
+		if (!wait_for_spinner(&spin_lo, rq)) {
+			pr_err("First context failed to start\n");
+			goto err_wedged;
+		}
+
+		rq = spinner_create_request(&spin_hi, ctx_hi, engine, MI_NOOP);
+		if (IS_ERR(rq)) {
+			spinner_end(&spin_lo);
+			err = PTR_ERR(rq);
+			goto err_ctx_lo;
+		}
+
+		i915_request_add(rq);
+		if (wait_for_spinner(&spin_hi, rq)) {
+			pr_err("Second context overtook first?\n");
+			goto err_wedged;
+		}
+
+		GEM_TRACE("%s rescheduling (no timeout)\n", engine->name);
+		engine->schedule(rq, &(struct i915_sched_attr){
+				 .priority = 1,
+				 }, 0);
+
+		if (wait_for_spinner(&spin_hi, rq)) {
+			pr_err("High priority context overtook first without an arbitration point?\n");
+			goto err_wedged;
+		}
+
+		GEM_TRACE("%s rescheduling (with timeout)\n", engine->name);
+		engine->schedule(rq, &(struct i915_sched_attr){
+				 .priority = 2,
+				 }, 10 * 1000 /* 10us */);
+
+		if (!wait_for_spinner(&spin_hi, rq)) {
+			pr_err("High priority context failed to force itself in front of the low priority context\n");
+			GEM_TRACE_DUMP();
+			goto err_wedged;
+		}
+
+		spinner_end(&spin_hi);
+		spinner_end(&spin_lo);
+		if (igt_flush_test(i915, I915_WAIT_LOCKED)) {
+			err = -EIO;
+			goto err_ctx_lo;
+		}
+	}
+
+	err = 0;
+err_ctx_lo:
+	kernel_context_close(ctx_lo);
+err_ctx_hi:
+	kernel_context_close(ctx_hi);
+err_spin_lo:
+	spinner_fini(&spin_lo);
+err_spin_hi:
+	spinner_fini(&spin_hi);
+err_unlock:
+	igt_flush_test(i915, I915_WAIT_LOCKED);
+	mutex_unlock(&i915->drm.struct_mutex);
+	return err;
+
+err_wedged:
+	spinner_end(&spin_hi);
+	spinner_end(&spin_lo);
+	i915_gem_set_wedged(i915);
+	err = -EIO;
+	goto err_ctx_lo;
+}
+
 int intel_execlists_live_selftests(struct drm_i915_private *i915)
 {
 	static const struct i915_subtest tests[] = {
@@ -626,6 +733,7 @@ int intel_execlists_live_selftests(struct drm_i915_private *i915)
 		SUBTEST(live_late_preempt),
 		SUBTEST(live_preempt_timeout),
 		SUBTEST(live_preempt_reset),
+		SUBTEST(live_late_preempt_timeout),
 	};
 
 	if (!HAS_EXECLISTS(i915))
-- 
2.17.0

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