timerqueue: Provide linked timerqueue

The hrtimer subsystem wants to peak ahead to the next and previous timer to
evaluated whether a to be rearmed timer can stay at the same position in
the RB tree with the new expiry time.

The linked RB tree provides the infrastructure for this as it maintains
links to the previous and next nodes for each entry in the tree.

Provide timerqueue wrappers around that.

Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260224163431.734827095@kernel.org

1 files changed, 14 insertions, 0 deletions

diff --git a/lib/timerqueue.c b/lib/timerqueue.c
index cdb9c7658478..e2a1e08cb4bd 100644
--- a/lib/timerqueue.c
+++ b/lib/timerqueue.c
@@ -82,3 +82,17 @@ struct timerqueue_node *timerqueue_iterate_next(struct timerqueue_node *node)
 	return container_of(next, struct timerqueue_node, node);
 }
 EXPORT_SYMBOL_GPL(timerqueue_iterate_next);
+
+#define __node_2_tq_linked(_n) \
+	container_of(rb_entry((_n), struct rb_node_linked, node), struct timerqueue_linked_node, node)
+
+static __always_inline bool __tq_linked_less(struct rb_node *a, const struct rb_node *b)
+{
+	return __node_2_tq_linked(a)->expires < __node_2_tq_linked(b)->expires;
+}
+
+bool timerqueue_linked_add(struct timerqueue_linked_head *head, struct timerqueue_linked_node *node)
+{
+	return rb_add_linked(&node->node, &head->rb_root, __tq_linked_less);
+}
+EXPORT_SYMBOL_GPL(timerqueue_linked_add);