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/include/linux/timerlist.h b/include/linux/timerlist.h
new file mode 100644 (file)
index 0000000..c46b28a
--- /dev/null
+++ b/include/linux/timerlist.h
@@ -0,0 +1,37 @@
+#ifndef _LINUX_TIMERLIST_H
+#define _LINUX_TIMERLIST_H
+
+#include <linux/rbtree.h>
+#include <linux/ktime.h>
+
+
+struct timerlist_node {
+       struct rb_node node;
+       ktime_t expires;
+};
+
+struct timerlist_head {
+       struct rb_root head;
+       struct timerlist_node *next;
+};
+
+
+extern void timerlist_add(struct timerlist_head *head,
+                               struct timerlist_node *node);
+extern void timerlist_del(struct timerlist_head *head,
+                               struct timerlist_node *node);
+extern struct timerlist_node *timerlist_getnext(struct timerlist_head *head);
+extern struct timerlist_node *timerlist_iterate_next(
+                                               struct timerlist_node *node);
+
+static inline void timerlist_init(struct timerlist_node *node)
+{
+       RB_CLEAR_NODE(&node->node);
+}
+
+static inline void timerlist_init_head(struct timerlist_head *head)
+{
+       head->head = RB_ROOT;
+       head->next = NULL;
+}
+#endif /* _LINUX_TIMERLIST_H */

diff --git a/lib/Makefile b/lib/Makefile
index e6a3763b82126729ecad6636caec9686cd7dec5f..8b475cfb819500acded4c239d20b4b88acf32074 100644 (file)
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -8,7 +8,7 @@ KBUILD_CFLAGS = $(subst -pg,,$(ORIG_CFLAGS))
 endif
 
 lib-y := ctype.o string.o vsprintf.o cmdline.o \
-        rbtree.o radix-tree.o dump_stack.o \
+        rbtree.o radix-tree.o dump_stack.o timerlist.o\
         idr.o int_sqrt.o extable.o prio_tree.o \
         sha1.o irq_regs.o reciprocal_div.o argv_split.o \
         proportions.o prio_heap.o ratelimit.o show_mem.o \

diff --git a/lib/timerlist.c b/lib/timerlist.c
new file mode 100644 (file)
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);
+}