tracing: Fix return of trace_dump_stack()

The trace_dump_stack() returned a value for a void function.

Also, added the missing stub for trace_dump_stack() when tracing is
not configured.
Reported-by: Ingo Molnar <mingo@elte.hu>
LKML-Reference: <20091214162713.GA31060@elte.hu>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/kernel.h

@@ -527,6 +527,7 @@ trace_printk(const char *fmt, ...) __attribute__ ((format (printf, 1, 2)));
 static inline void tracing_start(void) { }
 static inline void tracing_stop(void) { }
 static inline void ftrace_off_permanent(void) { }
+static inline void trace_dump_stack(void) { }
 static inline int
 trace_printk(const char *fmt, ...)
 {

kernel/trace/trace.c

@@ -1158,7 +1158,7 @@ void trace_dump_stack(void)
 	unsigned long flags;
 
 	if (tracing_disabled || tracing_selftest_running)
-		return 0;
+		return;
 
 	local_save_flags(flags);