perf ui: Serialize screen updates

The ui operations so far were used by just one thread, but 'perf top
--tui' now has two threads updating the screen, so we need to use a
mutex to avoid garbling the screen.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/Makefile b/tools/perf/Makefile
index bc4d9bf..ffd1047 100644
--- a/tools/perf/Makefile
+++ b/tools/perf/Makefile
@@ -637,6 +637,7 @@
 		LIB_H += util/ui/libslang.h
 		LIB_H += util/ui/progress.h
 		LIB_H += util/ui/util.h
+		LIB_H += util/ui/ui.h
 	endif
 endif