summaryrefslogtreecommitdiff
path: root/kernel/time/clocksource.c
diff options
context:
space:
mode:
Diffstat (limited to 'kernel/time/clocksource.c')
-rw-r--r--kernel/time/clocksource.c63
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;
}