[RFC 43/60] cosched: Add for_each_sched_entity() variant for owned entities

["Jan H. Schönherr" <jschoenh@amazon.de>]

Add a new loop constuct for_each_owned_sched_entity(), which iterates
over all owned scheduling entities, stopping when it encounters a
leader change.

This allows relatively straight-forward adaptations of existing code,
where the leader only handles that part of the hierarchy it actually
owns.

Include some lockdep goodness, so that we detect incorrect usage.

Signed-off-by: Jan H. Schönherr <jschoenh@amazon.de>
---
 kernel/sched/fair.c | 70 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index f72a72c8c3b8..f55954e7cedc 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -521,6 +521,76 @@ find_matching_se(struct sched_entity **se, struct sched_entity **pse)
 static __always_inline
 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
 
+#ifdef CONFIG_COSCHEDULING
+struct sched_entity *owned_parent_entity(struct sched_entity *se)
+{
+	struct rq *prq, *rq = hrq_of(cfs_rq_of(se));
+
+	lockdep_assert_held(&rq->lock);
+
+	se = parent_entity(se);
+	if (!se)
+		return NULL;
+
+	prq = hrq_of(cfs_rq_of(se));
+	if (rq == prq)
+		return se;
+
+#ifdef CONFIG_SCHED_DEBUG
+	if (!rq->sdrq_data.parent_locked) {
+		int leader = rq->sdrq_data.leader;
+		int pleader = READ_ONCE(prq->sdrq_data.leader);
+
+		SCHED_WARN_ON(leader == pleader);
+	} else {
+		int leader = rq->sdrq_data.leader;
+		int pleader = prq->sdrq_data.leader;
+
+		SCHED_WARN_ON(leader != pleader);
+	}
+#endif
+
+	if (!rq->sdrq_data.parent_locked)
+		return NULL;
+
+	lockdep_assert_held(&prq->lock);
+	return se;
+}
+
+static inline int leader_of(struct sched_entity *se)
+{
+	struct rq *rq = hrq_of(cfs_rq_of(se));
+
+	lockdep_assert_held(&rq->lock);
+	return rq->sdrq_data.leader;
+}
+
+static inline int __leader_of(struct sched_entity *se)
+{
+	struct rq *rq = hrq_of(cfs_rq_of(se));
+
+	return READ_ONCE(rq->sdrq_data.leader);
+}
+#else
+struct sched_entity *owned_parent_entity(struct sched_entity *se)
+{
+	return parent_entity(se);
+}
+
+static inline int leader_of(struct sched_entity *se)
+{
+	return cpu_of(rq_of(cfs_rq_of(se)));
+}
+
+static inline int __leader_of(struct sched_entity *se)
+{
+	return leader_of(se);
+}
+#endif
+
+#define for_each_owned_sched_entity(se) \
+	for (; se; se = owned_parent_entity(se))
+
 /**************************************************************
  * Scheduling class tree data structure manipulation methods:
  */
-- 
2.9.3.1.gcba166c.dirty