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, 48 insertions, 8 deletions

diff --git a/include/linux/timerqueue.h b/include/linux/timerqueue.h
index d306d9dd2207..7d0aaa766580 100644
--- a/include/linux/timerqueue.h
+++ b/include/linux/timerqueue.h
@@ -5,12 +5,11 @@
 #include <linux/rbtree.h>
 #include <linux/timerqueue_types.h>
 
-extern bool timerqueue_add(struct timerqueue_head *head,
-			   struct timerqueue_node *node);
-extern bool timerqueue_del(struct timerqueue_head *head,
-			   struct timerqueue_node *node);
-extern struct timerqueue_node *timerqueue_iterate_next(
-						struct timerqueue_node *node);
+bool timerqueue_add(struct timerqueue_head *head, struct timerqueue_node *node);
+bool timerqueue_del(struct timerqueue_head *head, struct timerqueue_node *node);
+struct timerqueue_node *timerqueue_iterate_next(struct timerqueue_node *node);
+
+bool timerqueue_linked_add(struct timerqueue_linked_head *head, struct timerqueue_linked_node *node);
 
 /**
  * timerqueue_getnext - Returns the timer with the earliest expiration time
@@ -19,8 +18,7 @@ extern struct timerqueue_node *timerqueue_iterate_next(
  *
  * Returns a pointer to the timer node that has the earliest expiration time.
  */
-static inline
-struct timerqueue_node *timerqueue_getnext(struct timerqueue_head *head)
+static inline struct timerqueue_node *timerqueue_getnext(struct timerqueue_head *head)
 {
 	struct rb_node *leftmost = rb_first_cached(&head->rb_root);
 
@@ -41,4 +39,46 @@ static inline void timerqueue_init_head(struct timerqueue_head *head)
 {
 	head->rb_root = RB_ROOT_CACHED;
 }
+
+/* Timer queues with linked nodes */
+
+static __always_inline
+struct timerqueue_linked_node *timerqueue_linked_first(struct timerqueue_linked_head *head)
+{
+	return rb_entry_safe(head->rb_root.rb_leftmost, struct timerqueue_linked_node, node);
+}
+
+static __always_inline
+struct timerqueue_linked_node *timerqueue_linked_next(struct timerqueue_linked_node *node)
+{
+	return rb_entry_safe(node->node.next, struct timerqueue_linked_node, node);
+}
+
+static __always_inline
+struct timerqueue_linked_node *timerqueue_linked_prev(struct timerqueue_linked_node *node)
+{
+	return rb_entry_safe(node->node.prev, struct timerqueue_linked_node, node);
+}
+
+static __always_inline
+bool timerqueue_linked_del(struct timerqueue_linked_head *head, struct timerqueue_linked_node *node)
+{
+	return rb_erase_linked(&node->node, &head->rb_root);
+}
+
+static __always_inline void timerqueue_linked_init(struct timerqueue_linked_node *node)
+{
+	RB_CLEAR_LINKED_NODE(&node->node);
+}
+
+static __always_inline bool timerqueue_linked_node_queued(struct timerqueue_linked_node *node)
+{
+	return !RB_EMPTY_LINKED_NODE(&node->node);
+}
+
+static __always_inline void timerqueue_linked_init_head(struct timerqueue_linked_head *head)
+{
+	head->rb_root = RB_ROOT_LINKED;
+}
+
 #endif /* _LINUX_TIMERQUEUE_H */