tracing: Export tracing clock functions

Critical tracepoint hooks should never call anything that takes a lock,
so they are unable to call getrawmonotonic() or ktime_get().

Export the rest of the tracing clock functions so can be used in
tracepoint hooks.

Background: We have a customer that adds their own module and registers
a tracepoint hook to sched_wakeup. They were using ktime_get() for a
time source, but it grabs a seq lock and caused a deadlock to occur.

Link: http://lkml.kernel.org/r/1430406624-22609-1-git-send-email-jsnitsel@redhat.com

Signed-off-by: Jerry Snitselaar <jsnitsel@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/trace_clock.c

@@ -56,6 +56,7 @@ u64 notrace trace_clock(void)
 {
 	return local_clock();
 }
+EXPORT_SYMBOL_GPL(trace_clock);
 
 /*
  * trace_jiffy_clock(): Simply use jiffies as a clock counter.
@@ -68,6 +69,7 @@ u64 notrace trace_clock_jiffies(void)
 {
 	return jiffies_64_to_clock_t(jiffies_64 - INITIAL_JIFFIES);
 }
+EXPORT_SYMBOL_GPL(trace_clock_jiffies);
 
 /*
  * trace_clock_global(): special globally coherent trace clock
@@ -123,6 +125,7 @@ u64 notrace trace_clock_global(void)
 
 	return now;
 }
+EXPORT_SYMBOL_GPL(trace_clock_global);
 
 static atomic64_t trace_counter;