[Intel-gfx] [PATCH 16/33] drm/i915/gt: Decouple completed requests on unwind

[Chris Wilson]

Since the introduction of preempt-to-busy, requests can complete in the
background, even while they are not on the engine->active.requests list.
As such, the engine->active.request list itself is not in strict
retirement order, and we have to scan the entire list while unwinding to
not miss any. However, if the request is completed we currently leave it
on the list [until retirement], but we could just as simply remove it
and stop treating it as active. We would only have to then traverse it
once while unwinding in quick succession.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/gt/intel_lrc.c | 6 ++++--
 drivers/gpu/drm/i915/i915_request.c | 3 ++-
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index c11433884cf6..0bcbd734a11d 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -1116,8 +1116,10 @@ __unwind_incomplete_requests(struct intel_engine_cs *engine)
 	list_for_each_entry_safe_reverse(rq, rn,
 					 &engine->active.requests,
 					 sched.link) {
-		if (i915_request_completed(rq))
-			continue; /* XXX */
+		if (i915_request_completed(rq)) {
+			list_del_init(&rq->sched.link);
+			continue;
+		}
 
 		__i915_request_unsubmit(rq);
 
diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index cebe07a85625..c3b7e8a0dae7 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -321,7 +321,8 @@ bool i915_request_retire(struct i915_request *rq)
 	 * after removing the breadcrumb and signaling it, so that we do not
 	 * inadvertently attach the breadcrumb to a completed request.
 	 */
-	remove_from_engine(rq);
+	if (!list_empty(&rq->sched.link))
+		remove_from_engine(rq);
 	GEM_BUG_ON(!llist_empty(&rq->execute_cb));
 
 	__list_del_entry(&rq->link); /* poison neither prev/next (RCU walks) */
-- 
2.20.1