[PATCH 01/11] reservation: add reservation_object_get_excl_unlocked()

[Rob Clark]

In the atomic modesetting path, each driver simply wants to grab a ref
to the exlusive fence from a reservation object to store in the incoming
drm_plane_state, without doing the whole RCU dance.  Since each driver
will need to do this, lets make a helper.

Signed-off-by: Rob Clark <robdclark at gmail.com>
---
 include/linux/reservation.h | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/include/linux/reservation.h b/include/linux/reservation.h
index 5a0b64c..7a018a9 100644
--- a/include/linux/reservation.h
+++ b/include/linux/reservation.h
@@ -120,6 +120,24 @@ reservation_object_get_excl(struct reservation_object *obj)
 					 reservation_object_held(obj));
 }
 
+static inline struct fence *
+reservation_object_get_excl_unlocked(struct reservation_object *obj)
+{
+	struct fence *fence;
+	unsigned seq;
+retry:
+	seq = read_seqcount_begin(&obj->seq);
+	rcu_read_lock();
+	fence = rcu_dereference(obj->fence_excl);
+	if (read_seqcount_retry(&obj->seq, seq)) {
+		rcu_read_unlock();
+		goto retry;
+	}
+	fence = fence_get(fence);
+	rcu_read_unlock();
+	return fence;
+}
+
 int reservation_object_reserve_shared(struct reservation_object *obj);
 void reservation_object_add_shared_fence(struct reservation_object *obj,
 					 struct fence *fence);
-- 
2.5.0