1 files changed, 42 insertions, 15 deletions

diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index e713ef7d19a7..50a8736757f3 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -181,6 +181,7 @@ static int finished_booting;
 
 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
 static void clocksource_watchdog_work(struct work_struct *work);
+static void clocksource_select(void);
 
 static LIST_HEAD(watchdog_list);
 static struct clocksource *watchdog;
@@ -301,13 +302,30 @@ static void clocksource_watchdog(unsigned long data)
                 if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) &&
                     (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) &&
                     (watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) {
+                        /* Mark it valid for high-res. */
                         cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
+
+                        /*
+                         * clocksource_done_booting() will sort it if
+                         * finished_booting is not set yet.
+                         */
+                        if (!finished_booting)
+                                continue;
+
                         /*
-                         * We just marked the clocksource as highres-capable,
-                         * notify the rest of the system as well so that we
-                         * transition into high-res mode:
+                         * If this is not the current clocksource let
+                         * the watchdog thread reselect it. Due to the
+                         * change to high res this clocksource might
+                         * be preferred now. If it is the current
+                         * clocksource let the tick code know about
+                         * that change.
                          */
-                        tick_clock_notify();
+                        if (cs != curr_clocksource) {
+                                cs->flags |= CLOCK_SOURCE_RESELECT;
+                                schedule_work(&watchdog_work);
+                        } else {
+                                tick_clock_notify();
+                        }
                 }
         }
 
@@ -404,19 +422,25 @@ static void clocksource_dequeue_watchdog(struct clocksource *cs)
         spin_unlock_irqrestore(&watchdog_lock, flags);
 }
 
-static int clocksource_watchdog_kthread(void *data)
+static int __clocksource_watchdog_kthread(void)
 {
         struct clocksource *cs, *tmp;
         unsigned long flags;
         LIST_HEAD(unstable);
+        int select = 0;
 
-        mutex_lock(&clocksource_mutex);
         spin_lock_irqsave(&watchdog_lock, flags);
-        list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list)
+        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);
+                        select = 1;
+                }
+                if (cs->flags & CLOCK_SOURCE_RESELECT) {
+                        cs->flags &= ~CLOCK_SOURCE_RESELECT;
+                        select = 1;
                 }
+        }
         /* Check if the watchdog timer needs to be stopped. */
         clocksource_stop_watchdog();
         spin_unlock_irqrestore(&watchdog_lock, flags);
@@ -426,6 +450,14 @@ static int clocksource_watchdog_kthread(void *data)
                 list_del_init(&cs->wd_list);
                 __clocksource_change_rating(cs, 0);
         }
+        return select;
+}
+
+static int clocksource_watchdog_kthread(void *data)
+{
+        mutex_lock(&clocksource_mutex);
+        if (__clocksource_watchdog_kthread())
+                clocksource_select();
         mutex_unlock(&clocksource_mutex);
         return 0;
 }
@@ -445,7 +477,7 @@ static void clocksource_enqueue_watchdog(struct clocksource *cs)
 
 static inline void clocksource_dequeue_watchdog(struct clocksource *cs) { }
 static inline void clocksource_resume_watchdog(void) { }
-static inline int clocksource_watchdog_kthread(void *data) { return 0; }
+static inline int __clocksource_watchdog_kthread(void) { return 0; }
 static bool clocksource_is_watchdog(struct clocksource *cs) { return false; }
 
 #endif /* CONFIG_CLOCKSOURCE_WATCHDOG */
@@ -647,16 +679,11 @@ static int __init clocksource_done_booting(void)
 {
         mutex_lock(&clocksource_mutex);
         curr_clocksource = clocksource_default_clock();
-        mutex_unlock(&clocksource_mutex);
-
         finished_booting = 1;
-
         /*
          * Run the watchdog first to eliminate unstable clock sources
          */
-        clocksource_watchdog_kthread(NULL);
-
-        mutex_lock(&clocksource_mutex);
+        __clocksource_watchdog_kthread();
         clocksource_select();
         mutex_unlock(&clocksource_mutex);
         return 0;
@@ -789,7 +816,6 @@ static void __clocksource_change_rating(struct clocksource *cs, int rating)
         list_del(&cs->list);
         cs->rating = rating;
         clocksource_enqueue(cs);
-        clocksource_select();
 }
 
 /**
@@ -801,6 +827,7 @@ void clocksource_change_rating(struct clocksource *cs, int rating)
 {
         mutex_lock(&clocksource_mutex);
         __clocksource_change_rating(cs, rating);
+        clocksource_select();
         mutex_unlock(&clocksource_mutex);
 }
 EXPORT_SYMBOL(clocksource_change_rating);