[Intel-gfx] [PATCH] drm/i915/execlists: Simply walk back along request timeline on reset

[Chris Wilson]

The request's timeline will only contain requests from this context, in
order of execution. Therefore, we can simply look back along this
timeline to find the currently executing request.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/gt/intel_lrc.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index 16340740139d..ef6dc6afd135 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -252,22 +252,16 @@ static void mark_eio(struct i915_request *rq)
 
 static struct i915_request *active_request(struct i915_request *rq)
 {
-	const struct intel_context * const ce = rq->hw_context;
 	struct i915_request *active = NULL;
 	struct list_head *list;
 
-	if (!i915_request_is_active(rq)) /* unwound, but incomplete! */
-		return rq;
-
 	rcu_read_lock();
 	list = &rcu_dereference(rq->timeline)->requests;
 	list_for_each_entry_from_reverse(rq, list, link) {
 		if (i915_request_completed(rq))
 			break;
 
-		if (rq->hw_context != ce)
-			break;
-
+		GEM_BUG_ON(!i915_request_is_active(rq));
 		active = rq;
 	}
 	rcu_read_unlock();
@@ -3000,6 +2994,7 @@ static void __execlists_reset(struct intel_engine_cs *engine, bool stalled)
 	/* Context has requests still in-flight; it should not be idle! */
 	GEM_BUG_ON(i915_active_is_idle(&ce->active));
 	ce->ring->head = intel_ring_wrap(ce->ring, rq->head);
+	GEM_BUG_ON(ce->ring->head == ce->ring->tail);
 
 	/*
 	 * If this request hasn't started yet, e.g. it is waiting on a
@@ -3043,7 +3038,7 @@ static void __execlists_reset(struct intel_engine_cs *engine, bool stalled)
 	restore_default_state(ce, engine);
 
 out_replay:
-	GEM_TRACE("%s replay {head:%04x, tail:%04x\n",
+	GEM_TRACE("%s replay {head:%04x, tail:%04x}\n",
 		  engine->name, ce->ring->head, ce->ring->tail);
 	intel_ring_update_space(ce->ring);
 	__execlists_reset_reg_state(ce, engine);
-- 
2.24.0.rc1