diff options
| -rw-r--r-- | arch/i386/kernel/tsc.c | 3 | ||||
| -rw-r--r-- | include/linux/clocksource.h | 6 | ||||
| -rw-r--r-- | kernel/time/clocksource.c | 120 |
3 files changed, 62 insertions, 67 deletions
diff --git a/arch/i386/kernel/tsc.c b/arch/i386/kernel/tsc.c index d4000649942..6f6971da761 100644 --- a/arch/i386/kernel/tsc.c +++ b/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; } diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h index 1622d23a8dc..55d71405237 100644 --- a/include/linux/clocksource.h +++ b/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 */ 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); |