Do an early read of the execlists' queue before we take the spinlock and
start checking. This is safe as the first writer to the execlists queue
will cause the tasklet to be run again after a memory barrier.
v2: Keep guc in sync with execlists queue changes
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>
Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Cc: Michał Winiarski <michal.winiarski@xxxxxxxxx>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>
Reviewed-by: Michał Winiarski <michal.winiarski@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_guc_submission.c | 4 ++++
drivers/gpu/drm/i915/intel_lrc.c | 4 ++++
2 files changed, 8 insertions(+)
diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c
index a3636b31ebc3..78718a8e70c3 100644
--- a/drivers/gpu/drm/i915/i915_guc_submission.c
+++ b/drivers/gpu/drm/i915/i915_guc_submission.c
@@ -577,6 +577,10 @@ static bool i915_guc_dequeue(struct intel_engine_cs *engine)
struct rb_node *rb;
bool submit = false;
+ /* After execlist_first is updated, a new tasklet must be scheduled */
+ if (!READ_ONCE(engine->execlist_first))
+ return false;
+
spin_lock_irqsave(&engine->timeline->lock, flags);
rb = engine->execlist_first;
while (rb) {
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index becde55b02a3..7adc588d1a19 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -403,6 +403,10 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
struct rb_node *rb;
bool submit = false;
+ /* After execlist_first is updated, a new tasklet must be scheduled */
+ if (!READ_ONCE(engine->execlist_first))
+ return;
+
last = port->request;
if (last)
/* WaIdleLiteRestore:bdw,skl
--
2.11.0
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