Merge "ARM: arch_timer: force re-selection of the best clocksource"

drivers/clocksource/arm_arch_timer.c

@@ -687,6 +687,7 @@ static void __init arch_timer_common_init(void)
 	arch_timer_banner(arch_timers_present);
 	arch_counter_register(arch_timers_present);
 	arch_timer_arch_init();
+	clocksource_select_force();
 }
 
 static void __init arch_timer_init(void)

include/linux/clocksource.h

@@ -186,6 +186,7 @@ extern void clocksource_suspend(void);
 extern void clocksource_resume(void);
 extern struct clocksource * __init clocksource_default_clock(void);
 extern void clocksource_mark_unstable(struct clocksource *cs);
+extern void clocksource_select_force(void);
 
 extern u64
 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cycles);

kernel/time/clocksource.c

@@ -108,7 +108,7 @@ static int finished_booting;
 
 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
 static void clocksource_watchdog_work(struct work_struct *work);
-static void clocksource_select(void);
+static void clocksource_select(bool force);
 
 static LIST_HEAD(watchdog_list);
 static struct clocksource *watchdog;
@@ -415,7 +415,7 @@ static int clocksource_watchdog_kthread(void *data)
 {
 	mutex_lock(&clocksource_mutex);
 	if (__clocksource_watchdog_kthread())
-		clocksource_select();
+		clocksource_select(false);
 	mutex_unlock(&clocksource_mutex);
 	return 0;
 }
@@ -555,11 +555,12 @@ static inline void clocksource_update_max_deferment(struct clocksource *cs)
 
 #ifndef CONFIG_ARCH_USES_GETTIMEOFFSET
 
-static struct clocksource *clocksource_find_best(bool oneshot, bool skipcur)
+static struct clocksource *clocksource_find_best(bool oneshot, bool skipcur,
+						bool force)
 {
 	struct clocksource *cs;
 
-	if (!finished_booting || list_empty(&clocksource_list))
+	if ((!finished_booting && !force) || list_empty(&clocksource_list))
 		return NULL;
 
 	/*
@@ -577,13 +578,13 @@ static struct clocksource *clocksource_find_best(bool oneshot, bool skipcur)
 	return NULL;
 }
 
-static void __clocksource_select(bool skipcur)
+static void __clocksource_select(bool skipcur, bool force)
 {
 	bool oneshot = tick_oneshot_mode_active();
 	struct clocksource *best, *cs;
 
 	/* Find the best suitable clocksource */
-	best = clocksource_find_best(oneshot, skipcur);
+	best = clocksource_find_best(oneshot, skipcur, force);
 	if (!best)
 		return;
 
@@ -623,22 +624,40 @@ static void __clocksource_select(bool skipcur)
  * Select the clocksource with the best rating, or the clocksource,
  * which is selected by userspace override.
  */
-static void clocksource_select(void)
+static void clocksource_select(bool force)
 {
-	__clocksource_select(false);
+	return __clocksource_select(false, force);
 }
 
 static void clocksource_select_fallback(void)
 {
-	__clocksource_select(true);
+	__clocksource_select(true, false);
 }
 
 #else /* !CONFIG_ARCH_USES_GETTIMEOFFSET */
-static inline void clocksource_select(void) { }
+
+static inline void clocksource_select(bool force) { }
 static inline void clocksource_select_fallback(void) { }
 
 #endif
 
+/**
+ * clocksource_select_force - Force re-selection of the best clocksource
+ *				among registered clocksources
+ *
+ * clocksource_select() can't select the best clocksource before
+ * calling clocksource_done_booting() and since clocksource_select()
+ * should be called with clocksource_mutex held, provide a new API
+ * can be called from other files to select best clockrouce irrespective
+ * of finished_booting flag.
+ */
+void clocksource_select_force(void)
+{
+	mutex_lock(&clocksource_mutex);
+	clocksource_select(true);
+	mutex_unlock(&clocksource_mutex);
+}
+
 /*
  * clocksource_done_booting - Called near the end of core bootup
  *
@@ -655,7 +674,7 @@ static int __init clocksource_done_booting(void)
 	 * Run the watchdog first to eliminate unstable clock sources
 	 */
 	__clocksource_watchdog_kthread();
-	clocksource_select();
+	clocksource_select(false);
 	mutex_unlock(&clocksource_mutex);
 	return 0;
 }
@@ -744,6 +763,7 @@ void __clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq
 }
 EXPORT_SYMBOL_GPL(__clocksource_update_freq_scale);
 
+
 /**
  * __clocksource_register_scale - Used to install new clocksources
  * @cs:		clocksource to be registered
@@ -765,7 +785,7 @@ int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq)
 	mutex_lock(&clocksource_mutex);
 	clocksource_enqueue(cs);
 	clocksource_enqueue_watchdog(cs);
-	clocksource_select();
+	clocksource_select(false);
 	clocksource_select_watchdog(false);
 	mutex_unlock(&clocksource_mutex);
 	return 0;
@@ -788,7 +808,7 @@ void clocksource_change_rating(struct clocksource *cs, int rating)
 {
 	mutex_lock(&clocksource_mutex);
 	__clocksource_change_rating(cs, rating);
-	clocksource_select();
+	clocksource_select(false);
 	clocksource_select_watchdog(false);
 	mutex_unlock(&clocksource_mutex);
 }
@@ -892,7 +912,7 @@ static ssize_t sysfs_override_clocksource(struct device *dev,
 
 	ret = sysfs_get_uname(buf, override_name, count);
 	if (ret >= 0)
-		clocksource_select();
+		clocksource_select(false);
 
 	mutex_unlock(&clocksource_mutex);