[Intel-gfx] [PATCH] drm/i915/execlists: Fixup cancel_port_requests()

[Chris Wilson]

I rushed a last minute correction to cancel_port_requests() to prevent
the snooping of *execlists->active as the inflight array was being
updated, without noticing we iterated the inflight array starting from
active! Oops.

Fixes: 331bf9059157 ("drm/i915/gt: Mark the execlists->active as the primary volatile access")
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
---
 drivers/gpu/drm/i915/gt/intel_lrc.c | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index e533ff7ba334..6090357a00fa 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -2007,19 +2007,17 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
 static void
 cancel_port_requests(struct intel_engine_execlists * const execlists)
 {
-	struct i915_request * const *port, *rq;
+	struct i915_request * const *port;
 
-	for (port = execlists->pending; (rq = *port); port++)
-		execlists_schedule_out(rq);
+	for (port = execlists->pending; *port; port++)
+		execlists_schedule_out(*port);
 	memset(execlists->pending, 0, sizeof(execlists->pending));
 
 	/* Mark the end of active before we overwrite *active */
-	WRITE_ONCE(execlists->active, execlists->pending);
-
-	for (port = execlists->active; (rq = *port); port++)
-		execlists_schedule_out(rq);
-	execlists->active =
-		memset(execlists->inflight, 0, sizeof(execlists->inflight));
+	for (port = xchg(&execlists->active, execlists->pending); *port; port++)
+		execlists_schedule_out(*port);
+	WRITE_ONCE(execlists->active,
+		   memset(execlists->inflight, 0, sizeof(execlists->inflight)));
 }
 
 static inline void
-- 
2.24.0