---

yaml
---
r: 48566
b: refs/heads/master
c: 92c7e00
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 26a08eb301a2e3fce5a501e3dd26cf3ec46591d7
+refs/heads/master: 92c7e00254b2d0efc1e36ac3e45474ce1871b6b2

trunk/arch/i386/kernel/tsc.c

@@ -323,8 +323,7 @@ static int tsc_update_callback(void)
 
 	/* check to see if we should switch to the safe clocksource: */
 	if (clocksource_tsc.rating != 0 && check_tsc_unstable()) {
-		clocksource_tsc.rating = 0;
-		clocksource_reselect();
+		clocksource_change_rating(&clocksource_tsc, 0);
 		change = 1;
 	}
 

trunk/include/linux/clocksource.h

@@ -178,8 +178,8 @@ static inline void clocksource_calculate_interval(struct clocksource *c,
 
 
 /* used to install a new clocksource */
-int clocksource_register(struct clocksource*);
-void clocksource_reselect(void);
-struct clocksource* clocksource_get_next(void);
+extern int clocksource_register(struct clocksource*);
+extern struct clocksource* clocksource_get_next(void);
+extern void clocksource_change_rating(struct clocksource *cs, int rating);
 
 #endif /* _LINUX_CLOCKSOURCE_H */

trunk/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
 /**
@@ -221,25 +198,44 @@ 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;
 
 	/* 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);