diff --git a/arch/x86/kernel/i8253.c b/arch/x86/kernel/i8253.c
index 0f8f35458a8f49397430521c04a69a8cf4b6ffb0..decc5d294d7631f8efc126201106c1c0c6bc46ab 100644
--- a/arch/x86/kernel/i8253.c
+++ b/arch/x86/kernel/i8253.c
@@ -13,6 +13,7 @@
 #include <asm/delay.h>
 #include <asm/i8253.h>
 #include <asm/io.h>
+#include <asm/hpet.h>
 
 DEFINE_SPINLOCK(i8253_lock);
 EXPORT_SYMBOL(i8253_lock);
diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index 07b42153de245b711e81467fad632aeec0feb486..85778a4b120906870970f25f8e987fdc7ece95e6 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -215,6 +215,7 @@ static inline void clocksource_calculate_interval(struct clocksource *c,
 
 /* used to install a new clocksource */
 extern int clocksource_register(struct clocksource*);
+extern void clocksource_unregister(struct clocksource*);
 extern struct clocksource* clocksource_get_next(void);
 extern void clocksource_change_rating(struct clocksource *cs, int rating);
 extern void clocksource_resume(void);
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index edd5ef8e1765800c8cdce8ed369e6392f371511f..6e9259a5d5010ac7e869f4f567fd3c0618002943 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -337,6 +337,21 @@ void clocksource_change_rating(struct clocksource *cs, int rating)
 	spin_unlock_irqrestore(&clocksource_lock, flags);
 }
 
+/**
+ * clocksource_unregister - remove a registered clocksource
+ */
+void clocksource_unregister(struct clocksource *cs)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&clocksource_lock, flags);
+	list_del(&cs->list);
+	if (clocksource_override == cs)
+		clocksource_override = NULL;
+	next_clocksource = select_clocksource();
+	spin_unlock_irqrestore(&clocksource_lock, flags);
+}
+
 #ifdef CONFIG_SYSFS
 /**
  * sysfs_show_current_clocksources - sysfs interface for current clocksource