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-rw-r--r--kernel/time/clocksource.c120
1 files changed, 58 insertions, 62 deletions
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index d9ef176c4e0..2f6a3d6e43b 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -48,6 +48,7 @@ extern struct clocksource clocksource_jiffies;
*/
static struct clocksource *curr_clocksource = &clocksource_jiffies;
static struct clocksource *next_clocksource;
+static struct clocksource *clocksource_override;
static LIST_HEAD(clocksource_list);
static DEFINE_SPINLOCK(clocksource_lock);
static char override_name[32];
@@ -84,60 +85,46 @@ struct clocksource *clocksource_get_next(void)
}
/**
- * select_clocksource - Finds the best registered clocksource.
+ * select_clocksource - Selects the best registered clocksource.
*
* Private function. Must hold clocksource_lock when called.
*
- * Looks through the list of registered clocksources, returning
- * the one with the highest rating value. If there is a clocksource
- * name that matches the override string, it returns that clocksource.
+ * Select the clocksource with the best rating, or the clocksource,
+ * which is selected by userspace override.
*/
static struct clocksource *select_clocksource(void)
{
- struct clocksource *best = NULL;
- struct list_head *tmp;
-
- list_for_each(tmp, &clocksource_list) {
- struct clocksource *src;
+ if (list_empty(&clocksource_list))
+ return NULL;
- src = list_entry(tmp, struct clocksource, list);
- if (!best)
- best = src;
-
- /* check for override: */
- if (strlen(src->name) == strlen(override_name) &&
- !strcmp(src->name, override_name)) {
- best = src;
- break;
- }
- /* pick the highest rating: */
- if (src->rating > best->rating)
- best = src;
- }
+ if (clocksource_override)
+ return clocksource_override;
- return best;
+ return list_entry(clocksource_list.next, struct clocksource, list);
}
-/**
- * is_registered_source - Checks if clocksource is registered
- * @c: pointer to a clocksource
- *
- * Private helper function. Must hold clocksource_lock when called.
- *
- * Returns one if the clocksource is already registered, zero otherwise.
+/*
+ * Enqueue the clocksource sorted by rating
*/
-static int is_registered_source(struct clocksource *c)
+static int clocksource_enqueue(struct clocksource *c)
{
- int len = strlen(c->name);
- struct list_head *tmp;
+ struct list_head *tmp, *entry = &clocksource_list;
list_for_each(tmp, &clocksource_list) {
- struct clocksource *src;
-
- src = list_entry(tmp, struct clocksource, list);
- if (strlen(src->name) == len && !strcmp(src->name, c->name))
- return 1;
+ struct clocksource *cs;
+
+ cs = list_entry(tmp, struct clocksource, list);
+ if (cs == c)
+ return -EBUSY;
+ /* Keep track of the place, where to insert */
+ if (cs->rating >= c->rating)
+ entry = tmp;
}
+ list_add(&c->list, entry);
+
+ if (strlen(c->name) == strlen(override_name) &&
+ !strcmp(c->name, override_name))
+ clocksource_override = c;
return 0;
}
@@ -150,42 +137,32 @@ static int is_registered_source(struct clocksource *c)
*/
int clocksource_register(struct clocksource *c)
{
- int ret = 0;
unsigned long flags;
+ int ret = 0;
spin_lock_irqsave(&clocksource_lock, flags);
- /* check if clocksource is already registered */
- if (is_registered_source(c)) {
- printk("register_clocksource: Cannot register %s. "
- "Already registered!", c->name);
- ret = -EBUSY;
- } else {
- /* register it */
- list_add(&c->list, &clocksource_list);
- /* scan the registered clocksources, and pick the best one */
+ ret = clocksource_enqueue(c);
+ if (!ret)
next_clocksource = select_clocksource();
- }
spin_unlock_irqrestore(&clocksource_lock, flags);
return ret;
}
EXPORT_SYMBOL(clocksource_register);
/**
- * clocksource_reselect - Rescan list for next clocksource
+ * clocksource_change_rating - Change the rating of a registered clocksource
*
- * A quick helper function to be used if a clocksource changes its
- * rating. Forces the clocksource list to be re-scanned for the best
- * clocksource.
*/
-void clocksource_reselect(void)
+void clocksource_change_rating(struct clocksource *cs, int rating)
{
unsigned long flags;
spin_lock_irqsave(&clocksource_lock, flags);
+ list_del(&cs->list);
+ clocksource_enqueue(cs);
next_clocksource = select_clocksource();
spin_unlock_irqrestore(&clocksource_lock, flags);
}
-EXPORT_SYMBOL(clocksource_reselect);
#ifdef CONFIG_SYSFS
/**
@@ -221,7 +198,11 @@ sysfs_show_current_clocksources(struct sys_device *dev, char *buf)
static ssize_t sysfs_override_clocksource(struct sys_device *dev,
const char *buf, size_t count)
{
+ struct clocksource *ovr = NULL;
+ struct list_head *tmp;
size_t ret = count;
+ int len;
+
/* strings from sysfs write are not 0 terminated! */
if (count >= sizeof(override_name))
return -EINVAL;
@@ -229,17 +210,32 @@ static ssize_t sysfs_override_clocksource(struct sys_device *dev,
/* strip of \n: */
if (buf[count-1] == '\n')
count--;
- if (count < 1)
- return -EINVAL;
spin_lock_irq(&clocksource_lock);
- /* copy the name given: */
- memcpy(override_name, buf, count);
+ if (count > 0)
+ memcpy(override_name, buf, count);
override_name[count] = 0;
- /* try to select it: */
- next_clocksource = select_clocksource();
+ len = strlen(override_name);
+ if (len) {
+ ovr = clocksource_override;
+ /* try to select it: */
+ list_for_each(tmp, &clocksource_list) {
+ struct clocksource *cs;
+
+ cs = list_entry(tmp, struct clocksource, list);
+ if (strlen(cs->name) == len &&
+ !strcmp(cs->name, override_name))
+ ovr = cs;
+ }
+ }
+
+ /* Reselect, when the override name has changed */
+ if (ovr != clocksource_override) {
+ clocksource_override = ovr;
+ next_clocksource = select_clocksource();
+ }
spin_unlock_irq(&clocksource_lock);