perf trace scripting: Fix extern struct definitions

Both python_scripting_ops and perl_scripting_ops have two global definitions.
One in trace-event-scripting.c and one in their respective scripting-engine
modules.

The issue is that depending on the linker order one definition or the other
is chosen. One is uninitialized (bss), while the other is initialized. If
the uninitialized version is chosen, then perf does not function properly.

This patch fixes this by adding the extern prefix to the definitions in
trace-event-scripting.c.

Cc: David S. Miller <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Robert Richter <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: Stephane Eranian <[email protected]>
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

tools/perf/util/trace-event-scripting.c

@@ -97,7 +97,7 @@ void setup_python_scripting(void)
 	register_python_scripting(&python_scripting_unsupported_ops);
 }
 #else
-struct scripting_ops python_scripting_ops;
+extern struct scripting_ops python_scripting_ops;
 
 void setup_python_scripting(void)
 {
@@ -158,7 +158,7 @@ void setup_perl_scripting(void)
 	register_perl_scripting(&perl_scripting_unsupported_ops);
 }
 #else
-struct scripting_ops perl_scripting_ops;
+extern struct scripting_ops perl_scripting_ops;
 
 void setup_perl_scripting(void)
 {