thr_once and !_REENTRANT libc

[Joerg Sonnenberger <joerg%britannica.bec.de@localhost>]

Hi all,
the attached patch allows code to use thread-safe initialisation without
having to worry about _REENTRANT. It should result in ~the same amount
of code as hand-roled solutions without requiring code duplication.

Joerg

Index: reentrant.h
===================================================================
RCS file: /btrfs/repo/netbsd/src/lib/libc/include/reentrant.h,v
retrieving revision 1.14
diff -u -p -r1.14 reentrant.h
--- reentrant.h 11 Jan 2009 02:46:28 -0000      1.14
+++ reentrant.h 1 Jun 2012 17:35:16 -0000
@@ -84,8 +84,6 @@
  *
  */
 
-#ifdef _REENTRANT
-
 /*
  * Abstract thread interface for thread-safe libraries.  These routines
  * will use stubs in libc if the application is not linked against the
@@ -124,6 +122,8 @@
 #define        once_t                  pthread_once_t
 #define        ONCE_INITIALIZER        PTHREAD_ONCE_INIT
 
+#ifdef _REENTRANT
+
 #ifndef __LIBC_THREAD_STUBS
 
 __BEGIN_DECLS
@@ -254,7 +254,15 @@ __END_DECLS
 #define        thr_getspecific(k)
 #define        thr_keydelete(k)
 
-#define        thr_once(o, f)
+static inline int
+thr_once(once_t *once_control, void (*routine)(void))
+{
+       if (__predict_false(once_control->pto_done == 0)) {
+               (*routine)();
+               once_control->pto_done = 1;
+       }
+       return 0;
+}
 #define        thr_sigsetmask(f, n, o)
 #define        thr_self()
 #define        thr_errno()