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clocksource: Let clocksource_unregister() return success/error 

The unregister call can fail, if the clocksource is the current one
and there is no replacement clocksource available. It can also fail,
if the clocksource is the watchdog clocksource and I'm not going to
provide support for this.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Magnus Damm <magnus.damm@gmail.com>
Link: http://lkml.kernel.org/r/20130425143436.029915527@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Thomas Gleixner 2013-04-25 20:31:46 +00:00
parent 7eaeb34305
commit a89c7edbe7
2 changed files with 13 additions and 22 deletions
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2
include/linux/clocksource.h
View File

@ -282,7 +282,7 @@ static inline s64 clocksource_cyc2ns(cycle_t cycles, u32 mult, u32 shift)
extern int clocksource_register(struct clocksource*);
extern void clocksource_unregister(struct clocksource*);
extern int clocksource_unregister(struct clocksource*);
extern void clocksource_touch_watchdog(void);
extern struct clocksource* clocksource_get_next(void);
extern void clocksource_change_rating(struct clocksource *cs, int rating);

33
kernel/time/clocksource.c
View File

@ -389,28 +389,17 @@ static void clocksource_enqueue_watchdog(struct clocksource *cs)
static void clocksource_dequeue_watchdog(struct clocksource *cs)
{
struct clocksource *tmp;
unsigned long flags;
spin_lock_irqsave(&watchdog_lock, flags);
if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
/* cs is a watched clocksource. */
list_del_init(&cs->wd_list);
} else if (cs == watchdog) {
/* Reset watchdog cycles */
clocksource_reset_watchdog();
/* Current watchdog is removed. Find an alternative. */
watchdog = NULL;
list_for_each_entry(tmp, &clocksource_list, list) {
if (tmp == cs || tmp->flags & CLOCK_SOURCE_MUST_VERIFY)
continue;
if (!watchdog || tmp->rating > watchdog->rating)
watchdog = tmp;
if (cs != watchdog) {
if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
/* cs is a watched clocksource. */
list_del_init(&cs->wd_list);
/* Check if the watchdog timer needs to be stopped. */
clocksource_stop_watchdog();
}
}
cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
/* Check if the watchdog timer needs to be stopped. */
clocksource_stop_watchdog();
spin_unlock_irqrestore(&watchdog_lock, flags);
}
@ -841,13 +830,15 @@ static int clocksource_unbind(struct clocksource *cs)
* clocksource_unregister - remove a registered clocksource
* @cs: clocksource to be unregistered
*/
void clocksource_unregister(struct clocksource *cs)
int clocksource_unregister(struct clocksource *cs)
{
int ret = 0;
mutex_lock(&clocksource_mutex);
clocksource_dequeue_watchdog(cs);
list_del(&cs->list);
clocksource_select();
if (!list_empty(&cs->list))
ret = clocksource_unbind(cs);
mutex_unlock(&clocksource_mutex);
return ret;
}
EXPORT_SYMBOL(clocksource_unregister);