diff options
Diffstat (limited to 'kernel/time/clocksource.c')
| -rw-r--r-- | kernel/time/clocksource.c | 63 |
1 files changed, 44 insertions, 19 deletions
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c index 0e974cface0b..84f37420fcf5 100644 --- a/kernel/time/clocksource.c +++ b/kernel/time/clocksource.c @@ -119,6 +119,16 @@ static DEFINE_SPINLOCK(watchdog_lock); static int watchdog_running; static atomic_t watchdog_reset_pending; +static void inline clocksource_watchdog_lock(unsigned long *flags) +{ + spin_lock_irqsave(&watchdog_lock, *flags); +} + +static void inline clocksource_watchdog_unlock(unsigned long *flags) +{ + spin_unlock_irqrestore(&watchdog_lock, *flags); +} + static int clocksource_watchdog_kthread(void *data); static void __clocksource_change_rating(struct clocksource *cs, int rating); @@ -142,9 +152,19 @@ static void __clocksource_unstable(struct clocksource *cs) cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG); cs->flags |= CLOCK_SOURCE_UNSTABLE; + /* + * If the clocksource is registered clocksource_watchdog_kthread() will + * re-rate and re-select. + */ + if (list_empty(&cs->list)) { + cs->rating = 0; + return; + } + if (cs->mark_unstable) cs->mark_unstable(cs); + /* kick clocksource_watchdog_kthread() */ if (finished_booting) schedule_work(&watchdog_work); } @@ -153,10 +173,8 @@ static void __clocksource_unstable(struct clocksource *cs) * clocksource_mark_unstable - mark clocksource unstable via watchdog * @cs: clocksource to be marked unstable * - * This function is called instead of clocksource_change_rating from - * cpu hotplug code to avoid a deadlock between the clocksource mutex - * and the cpu hotplug mutex. It defers the update of the clocksource - * to the watchdog thread. + * This function is called by the x86 TSC code to mark clocksources as unstable; + * it defers demotion and re-selection to a kthread. */ void clocksource_mark_unstable(struct clocksource *cs) { @@ -164,7 +182,7 @@ void clocksource_mark_unstable(struct clocksource *cs) spin_lock_irqsave(&watchdog_lock, flags); if (!(cs->flags & CLOCK_SOURCE_UNSTABLE)) { - if (list_empty(&cs->wd_list)) + if (!list_empty(&cs->list) && list_empty(&cs->wd_list)) list_add(&cs->wd_list, &watchdog_list); __clocksource_unstable(cs); } @@ -319,9 +337,8 @@ static void clocksource_resume_watchdog(void) static void clocksource_enqueue_watchdog(struct clocksource *cs) { - unsigned long flags; + INIT_LIST_HEAD(&cs->wd_list); - spin_lock_irqsave(&watchdog_lock, flags); if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) { /* cs is a clocksource to be watched. */ list_add(&cs->wd_list, &watchdog_list); @@ -331,7 +348,6 @@ static void clocksource_enqueue_watchdog(struct clocksource *cs) if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; } - spin_unlock_irqrestore(&watchdog_lock, flags); } static void clocksource_select_watchdog(bool fallback) @@ -373,9 +389,6 @@ static void clocksource_select_watchdog(bool fallback) static void clocksource_dequeue_watchdog(struct clocksource *cs) { - unsigned long flags; - - spin_lock_irqsave(&watchdog_lock, flags); if (cs != watchdog) { if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) { /* cs is a watched clocksource. */ @@ -384,21 +397,19 @@ static void clocksource_dequeue_watchdog(struct clocksource *cs) clocksource_stop_watchdog(); } } - spin_unlock_irqrestore(&watchdog_lock, flags); } static int __clocksource_watchdog_kthread(void) { struct clocksource *cs, *tmp; unsigned long flags; - LIST_HEAD(unstable); int select = 0; spin_lock_irqsave(&watchdog_lock, flags); list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list) { if (cs->flags & CLOCK_SOURCE_UNSTABLE) { list_del_init(&cs->wd_list); - list_add(&cs->wd_list, &unstable); + __clocksource_change_rating(cs, 0); select = 1; } if (cs->flags & CLOCK_SOURCE_RESELECT) { @@ -410,11 +421,6 @@ static int __clocksource_watchdog_kthread(void) clocksource_stop_watchdog(); spin_unlock_irqrestore(&watchdog_lock, flags); - /* Needs to be done outside of watchdog lock */ - list_for_each_entry_safe(cs, tmp, &unstable, wd_list) { - list_del_init(&cs->wd_list); - __clocksource_change_rating(cs, 0); - } return select; } @@ -447,6 +453,9 @@ static inline int __clocksource_watchdog_kthread(void) { return 0; } static bool clocksource_is_watchdog(struct clocksource *cs) { return false; } void clocksource_mark_unstable(struct clocksource *cs) { } +static void inline clocksource_watchdog_lock(unsigned long *flags) { } +static void inline clocksource_watchdog_unlock(unsigned long *flags) { } + #endif /* CONFIG_CLOCKSOURCE_WATCHDOG */ /** @@ -779,14 +788,19 @@ EXPORT_SYMBOL_GPL(__clocksource_update_freq_scale); */ int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq) { + unsigned long flags; /* Initialize mult/shift and max_idle_ns */ __clocksource_update_freq_scale(cs, scale, freq); /* Add clocksource to the clocksource list */ mutex_lock(&clocksource_mutex); + + clocksource_watchdog_lock(&flags); clocksource_enqueue(cs); clocksource_enqueue_watchdog(cs); + clocksource_watchdog_unlock(&flags); + clocksource_select(); clocksource_select_watchdog(false); mutex_unlock(&clocksource_mutex); @@ -808,8 +822,13 @@ static void __clocksource_change_rating(struct clocksource *cs, int rating) */ void clocksource_change_rating(struct clocksource *cs, int rating) { + unsigned long flags; + mutex_lock(&clocksource_mutex); + clocksource_watchdog_lock(&flags); __clocksource_change_rating(cs, rating); + clocksource_watchdog_unlock(&flags); + clocksource_select(); clocksource_select_watchdog(false); mutex_unlock(&clocksource_mutex); @@ -821,6 +840,8 @@ EXPORT_SYMBOL(clocksource_change_rating); */ static int clocksource_unbind(struct clocksource *cs) { + unsigned long flags; + if (clocksource_is_watchdog(cs)) { /* Select and try to install a replacement watchdog. */ clocksource_select_watchdog(true); @@ -834,8 +855,12 @@ static int clocksource_unbind(struct clocksource *cs) if (curr_clocksource == cs) return -EBUSY; } + + clocksource_watchdog_lock(&flags); clocksource_dequeue_watchdog(cs); list_del_init(&cs->list); + clocksource_watchdog_unlock(&flags); + return 0; } |