Apparently on AIX when using gcc you need to call pthread_init()

gvanrossum · gvanrossum · commit d21744a1dd1f · 1998-09-10T03:04:40.000Z
(which is not a POSIX threads call!).  Reported and confirmed by Brad
Howes.
diff --git a/Python/thread_pthread.h b/Python/thread_pthread.h
@@ -120,6 +120,9 @@ typedef struct {
  */
 static void _init_thread _P0()
 {
+#if defined(_AIX) && defined(__GNUC__)
+	pthread_init();
+#endif
 }
 
 /*
