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>

2 files changed, 119 insertions, 1 deletions

diff --git a/lib/Makefile b/lib/Makefile
index e6a3763b8212..8b475cfb8195 100644
--- 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
index 000000000000..9101b42fd13d
--- /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);
+}