[Intel-gfx] [CI 12/12] drm/i915: Extract the ability to defer and rerun a request later

From: Chris Wilson <chris@chris-wilson.co.uk>
To: intel-gfx@lists.freedesktop.org
Subject: [Intel-gfx] [CI 12/12] drm/i915: Extract the ability to defer and rerun a request later
Date: Wed,  3 Feb 2021 11:18:06 +0000	[thread overview]
Message-ID: <20210203111806.7311-12-chris@chris-wilson.co.uk> (raw)
In-Reply-To: <20210203111806.7311-1-chris@chris-wilson.co.uk>

Lift the ability to defer a request until later from execlists into the
common layer.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
---
 .../drm/i915/gt/intel_execlists_submission.c  | 57 +++--------------
 drivers/gpu/drm/i915/i915_scheduler.c         | 63 +++++++++++++++++--
 drivers/gpu/drm/i915/i915_scheduler.h         |  5 +-
 3 files changed, 67 insertions(+), 58 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
index 310c248efa0b..9d24d91f5ae7 100644
--- a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
+++ b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
@@ -979,54 +979,6 @@ static void virtual_xfer_context(struct virtual_engine *ve,
 	}
 }
 
-static void defer_request(struct i915_request *rq, struct list_head * const pl)
-{
-	LIST_HEAD(list);
-
-	/*
-	 * We want to move the interrupted request to the back of
-	 * the round-robin list (i.e. its priority level), but
-	 * in doing so, we must then move all requests that were in
-	 * flight and were waiting for the interrupted request to
-	 * be run after it again.
-	 */
-	do {
-		struct i915_dependency *p;
-
-		GEM_BUG_ON(i915_request_is_active(rq));
-		list_move_tail(&rq->sched.link, pl);
-
-		for_each_waiter(p, rq) {
-			struct i915_request *w =
-				container_of(p->waiter, typeof(*w), sched);
-
-			if (p->flags & I915_DEPENDENCY_WEAK)
-				continue;
-
-			/* Leave semaphores spinning on the other engines */
-			if (w->engine != rq->engine)
-				continue;
-
-			/* No waiter should start before its signaler */
-			GEM_BUG_ON(i915_request_has_initial_breadcrumb(w) &&
-				   __i915_request_has_started(w) &&
-				   !__i915_request_is_complete(rq));
-
-			if (!i915_request_is_ready(w))
-				continue;
-
-			if (rq_prio(w) < rq_prio(rq))
-				continue;
-
-			GEM_BUG_ON(rq_prio(w) > rq_prio(rq));
-			GEM_BUG_ON(i915_request_is_active(w));
-			list_move_tail(&w->sched.link, &list);
-		}
-
-		rq = list_first_entry_or_null(&list, typeof(*rq), sched.link);
-	} while (rq);
-}
-
 static void defer_active(struct intel_engine_cs *engine)
 {
 	struct i915_request *rq;
@@ -1035,7 +987,14 @@ static void defer_active(struct intel_engine_cs *engine)
 	if (!rq)
 		return;
 
-	defer_request(rq, i915_sched_lookup_priolist(engine, rq_prio(rq)));
+	/*
+	 * We want to move the interrupted request to the back of
+	 * the round-robin list (i.e. its priority level), but
+	 * in doing so, we must then move all requests that were in
+	 * flight and were waiting for the interrupted request to
+	 * be run after it again.
+	 */
+	__i915_sched_defer_request(engine, rq);
 }
 
 static bool
diff --git a/drivers/gpu/drm/i915/i915_scheduler.c b/drivers/gpu/drm/i915/i915_scheduler.c
index a5df27061c3c..641141f3ce10 100644
--- a/drivers/gpu/drm/i915/i915_scheduler.c
+++ b/drivers/gpu/drm/i915/i915_scheduler.c
@@ -179,8 +179,8 @@ static void assert_priolists(struct intel_engine_execlists * const execlists)
 	}
 }
 
-struct list_head *
-i915_sched_lookup_priolist(struct intel_engine_cs *engine, int prio)
+static struct list_head *
+lookup_priolist(struct intel_engine_cs *engine, int prio)
 {
 	struct intel_engine_execlists * const execlists = &engine->execlists;
 	struct i915_priolist *p;
@@ -332,7 +332,7 @@ static void __i915_request_set_priority(struct i915_request *rq, int prio)
 	struct list_head *pos = &rq->sched.signalers_list;
 	struct list_head *plist;
 
-	plist = i915_sched_lookup_priolist(engine, prio);
+	plist = lookup_priolist(engine, prio);
 
 	/*
 	 * Recursively bump all dependent priorities to match the new request.
@@ -463,12 +463,63 @@ void i915_request_set_priority(struct i915_request *rq, int prio)
 	spin_unlock_irqrestore(&engine->active.lock, flags);
 }
 
+void __i915_sched_defer_request(struct intel_engine_cs *engine,
+				struct i915_request *rq)
+{
+	struct list_head *pl;
+	LIST_HEAD(list);
+
+	lockdep_assert_held(&engine->active.lock);
+	GEM_BUG_ON(!test_bit(I915_FENCE_FLAG_PQUEUE, &rq->fence.flags));
+
+	/*
+	 * When we defer a request, we must maintain its order with respect
+	 * to those that are waiting upon it. So we traverse its chain of
+	 * waiters and move any that are earlier than the request to after it.
+	 */
+	pl = lookup_priolist(engine, rq_prio(rq));
+	do {
+		struct i915_dependency *p;
+
+		GEM_BUG_ON(i915_request_is_active(rq));
+		list_move_tail(&rq->sched.link, pl);
+
+		for_each_waiter(p, rq) {
+			struct i915_request *w =
+				container_of(p->waiter, typeof(*w), sched);
+
+			if (p->flags & I915_DEPENDENCY_WEAK)
+				continue;
+
+			/* Leave semaphores spinning on the other engines */
+			if (w->engine != engine)
+				continue;
+
+			/* No waiter should start before its signaler */
+			GEM_BUG_ON(i915_request_has_initial_breadcrumb(w) &&
+				   __i915_request_has_started(w) &&
+				   !__i915_request_is_complete(rq));
+
+			if (!i915_request_is_ready(w))
+				continue;
+
+			if (rq_prio(w) < rq_prio(rq))
+				continue;
+
+			GEM_BUG_ON(rq_prio(w) > rq_prio(rq));
+			GEM_BUG_ON(i915_request_is_active(w));
+			list_move_tail(&w->sched.link, &list);
+		}
+
+		rq = list_first_entry_or_null(&list, typeof(*rq), sched.link);
+	} while (rq);
+}
+
 static void queue_request(struct intel_engine_cs *engine,
 			  struct i915_request *rq)
 {
 	GEM_BUG_ON(!list_empty(&rq->sched.link));
-	list_add_tail(&rq->sched.link,
-		      i915_sched_lookup_priolist(engine, rq_prio(rq)));
+	list_add_tail(&rq->sched.link, lookup_priolist(engine, rq_prio(rq)));
 	set_bit(I915_FENCE_FLAG_PQUEUE, &rq->fence.flags);
 }
 
@@ -567,7 +618,7 @@ __i915_sched_rewind_requests(struct intel_engine_cs *engine)
 		GEM_BUG_ON(rq_prio(rq) == I915_PRIORITY_INVALID);
 		if (rq_prio(rq) != prio) {
 			prio = rq_prio(rq);
-			pl = i915_sched_lookup_priolist(engine, prio);
+			pl = lookup_priolist(engine, prio);
 		}
 		GEM_BUG_ON(RB_EMPTY_ROOT(&engine->execlists.queue.rb_root));
 
diff --git a/drivers/gpu/drm/i915/i915_scheduler.h b/drivers/gpu/drm/i915/i915_scheduler.h
index 9860459fedb1..00ce0a9d519d 100644
--- a/drivers/gpu/drm/i915/i915_scheduler.h
+++ b/drivers/gpu/drm/i915/i915_scheduler.h
@@ -44,6 +44,8 @@ void i915_request_enqueue(struct i915_request *request);
 
 struct i915_request *
 __i915_sched_rewind_requests(struct intel_engine_cs *engine);
+void __i915_sched_defer_request(struct intel_engine_cs *engine,
+				struct i915_request *request);
 
 bool __i915_sched_suspend_request(struct intel_engine_cs *engine,
 				  struct i915_request *rq);
@@ -55,9 +57,6 @@ bool i915_sched_suspend_request(struct intel_engine_cs *engine,
 void i915_sched_resume_request(struct intel_engine_cs *engine,
 			       struct i915_request *rq);
 
-struct list_head *
-i915_sched_lookup_priolist(struct intel_engine_cs *engine, int prio);
-
 void __i915_priolist_free(struct i915_priolist *p);
 static inline void i915_priolist_free(struct i915_priolist *p)
 {
-- 
2.20.1

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