Add an interface for drivers to be notified of changes to CPU frequency.

cpufreq_pre_change is called before the change, giving each driver a chance
to revoke the change.  cpufreq_post_change provides the results of the
change (success or failure).  cpufreq_levels_changed gives the unit number
of the cpufreq device whose number of available levels has changed.  Hook
in all the drivers I could find that needed it.

* TSC: update TSC frequency value.  When the available levels change, take the
highest possible level and notify the timecounter set_cputicker() of that
freq.  This gets rid of the "calcru: runtime went backwards" messages.
* identcpu: updates the sysctl hw.clockrate value
* Profiling: if profiling is active when the clock changes, let the user
know the results may be inaccurate.

Reviewed by:	bde, phk
MFC after:	1 month

1 files changed, 11 insertions, 0 deletions

diff --git a/sys/sys/eventhandler.h b/sys/sys/eventhandler.h
index f4f1b8c..d18b635 100644
--- a/sys/sys/eventhandler.h
+++ b/sys/sys/eventhandler.h
@@ -104,6 +104,17 @@ struct eventhandler_entry_ ## name 					\
 };									\
 struct __hack
 
+#define EVENTHANDLER_DEFINE(name, func, arg, priority)			\
+	static eventhandler_tag name ## _tag;				\
+	static void name ## _evh_init(void *ctx)			\
+	{								\
+		name ## _tag = EVENTHANDLER_REGISTER(name, func, ctx,	\
+		    priority);						\
+	}								\
+	SYSINIT(name ## _evh_init, SI_SUB_CONFIGURE, SI_ORDER_ANY,	\
+	    name ## _evh_init, arg)					\
+	struct __hack
+
 #define EVENTHANDLER_INVOKE(name, ...)					\
 do {									\
 	struct eventhandler_list *_el;					\