From: Thomas Gleixner <tglx@linutronix.de>
Date: Wed, 30 Jan 2008 12:30:02 +0000 (+0100)
Subject: clocksource: add unregister function to disable unusable clocksources
X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=4713e22ce81eb8b3353e16435362eb3d0ec95640;p=deliverable%2Flinux.git

clocksource: add unregister function to disable unusable clocksources

On x86 the PIT might become an unusable clocksource. Add an unregister
function to provide a possibilty to remove the PIT from the list of
available clock sources.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

diff --git a/arch/x86/kernel/i8253.c b/arch/x86/kernel/i8253.c
index 0f8f35458a8f..decc5d294d76 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 07b42153de24..85778a4b1209 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 edd5ef8e1765..6e9259a5d501 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