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>
This commit is contained in:
John Stultz 2010-09-20 17:42:46 -07:00
parent 5e4f083f78
commit 87de5ac782
3 changed files with 156 additions and 1 deletions

37
include/linux/timerlist.h Normal file
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@ -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 */

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@ -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 \

118
lib/timerlist.c Normal file
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@ -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);
}