timers: Introduce timerlist infrastructure.
The timerlist infrastructure is a thin layer over the rbtree
code that implements a simple list of timers sorted by an
expires value, and a getnext function that provides a pointer
to the earliest timer.
This infrastructure allows drivers and other kernel infrastructure
to easily implement timers without duplicating code.
Signed-off-by: John Stultz <john.stultz@linaro.org>
LKML Reference: <1290136329-18291-2-git-send-email-john.stultz@linaro.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
CC: Alessandro Zummo <a.zummo@towertech.it>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Richard Cochran <richardcochran@gmail.com>
diff --git a/lib/timerlist.c b/lib/timerlist.c
new file mode 100644
index 0000000..9101b42
--- /dev/null
+++ b/lib/timerlist.c
@@ -0,0 +1,118 @@
+/*
+ * Generic Timer-list
+ *
+ * Manages a simple list of timers, ordered by expiration time.
+ * Uses rbtrees for quick list adds and expiration.
+ *
+ * NOTE: All of the following functions need to be serialized
+ * to avoid races. No locking is done by this libary code.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#include <linux/timerlist.h>
+#include <linux/rbtree.h>
+
+/**
+ * timerlist_add - Adds timer to timerlist.
+ *
+ * @head: head of timerlist
+ * @node: timer node to be added
+ *
+ * Adds the timer node to the timerlist, sorted by the
+ * node's expires value.
+ */
+void timerlist_add(struct timerlist_head *head, struct timerlist_node *node)
+{
+ struct rb_node **p = &head->head.rb_node;
+ struct rb_node *parent = NULL;
+ struct timerlist_node *ptr;
+
+ /* Make sure we don't add nodes that are already added */
+ WARN_ON_ONCE(!RB_EMPTY_NODE(&node->node));
+
+ while (*p) {
+ parent = *p;
+ ptr = rb_entry(parent, struct timerlist_node, node);
+ if (node->expires.tv64 < ptr->expires.tv64)
+ p = &(*p)->rb_left;
+ else
+ p = &(*p)->rb_right;
+ }
+ rb_link_node(&node->node, parent, p);
+ rb_insert_color(&node->node, &head->head);
+
+ if (!head->next || node->expires.tv64 < head->next->expires.tv64)
+ head->next = node;
+}
+
+/**
+ * timerlist_del - Removes a timer from the timerlist.
+ *
+ * @head: head of timerlist
+ * @node: timer node to be removed
+ *
+ * Removes the timer node from the timerlist.
+ */
+void timerlist_del(struct timerlist_head *head, struct timerlist_node *node)
+{
+ WARN_ON_ONCE(RB_EMPTY_NODE(&node->node));
+
+ /* update next pointer */
+ if (head->next == node) {
+ struct rb_node *rbn = rb_next(&node->node);
+
+ head->next = rbn ?
+ rb_entry(rbn, struct timerlist_node, node) : NULL;
+ }
+ rb_erase(&node->node, &head->head);
+ RB_CLEAR_NODE(&node->node);
+}
+
+
+/**
+ * timerlist_getnext - Returns the timer with the earlies expiration time
+ *
+ * @head: head of timerlist
+ *
+ * Returns a pointer to the timer node that has the
+ * earliest expiration time.
+ */
+struct timerlist_node *timerlist_getnext(struct timerlist_head *head)
+{
+ return head->next;
+}
+
+
+/**
+ * timerlist_iterate_next - Returns the timer after the provided timer
+ *
+ * @node: Pointer to a timer.
+ *
+ * Provides the timer that is after the given node. This is used, when
+ * necessary, to iterate through the list of timers in a timer list
+ * without modifying the list.
+ */
+struct timerlist_node *timerlist_iterate_next(struct timerlist_node *node)
+{
+ struct rb_node *next;
+
+ if (!node)
+ return NULL;
+ next = rb_next(&node->node);
+ if (!next)
+ return NULL;
+ return container_of(next, struct timerlist_node, node);
+}