perf tui: Make ui__warning modal

By taking the ui__lock so that no other screen updates take place while
waiting for the user.

That was happening when handling an invalid --vmlinux parameter in 'perf
top --tui', with the screen refresh routine repainting the screen and
removing the warning window.

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>

tools/perf/util/ui/util.c

@@ -9,6 +9,7 @@
 #include "../debug.h"
 #include "browser.h"
 #include "helpline.h"
+#include "ui.h"
 #include "util.h"
 
 static void newt_form__set_exit_keys(newtComponent self)
@@ -118,10 +119,12 @@ void ui__warning(const char *format, ...)
 	va_list args;
 
 	va_start(args, format);
-	if (use_browser > 0)
+	if (use_browser > 0) {
+		pthread_mutex_lock(&ui__lock);
 		newtWinMessagev((char *)warning_str, (char *)ok,
 				(char *)format, args);
-	else
+		pthread_mutex_unlock(&ui__lock);
+	} else
 		vfprintf(stderr, format, args);
 	va_end(args);
 }