pthread: (partial) merge once code from redhat win32 pthread.

git-svn-id: http://svn.netlabs.org/repos/ports/pthread/trunk@224 8d6eb4b1-0faa-de11-b929-00e081727c95

src/my_os2thread.c

@@ -7,6 +7,8 @@
 #include <string.h>
 #include <process.h>
 #include <types.h>
+#include <sys/builtin.h>
+
 #include "pthread.h"
 
 #undef pthread_exit
@@ -166,16 +168,24 @@ int pthread_once(pthread_once_t *once_control, void (*init_routine)(void))
 {
   pthread_mutex_t THR_LOCK_once;
 
-  // protect init
-  pthread_mutex_lock(&THR_LOCK_once);
+  if (once_control == NULL || init_routine == NULL)
+    {
+      return EINVAL;
+    }
 
-  if (*once_control == (pthread_once_t)PTHREAD_ONCE_INIT)
-  {
-     *once_control = 0;
-     init_routine();
-  }
+  if (!__atomic_xchg((unsigned)&once_control->done, 0)) /* MBR fence */
+    {
+      pthread_mutex_lock(&once_control->lock);
+
+      if (!once_control->done)
+	{
+	  (*init_routine)();
+	  once_control->done = PTW32_TRUE;
+	}
+
+	pthread_mutex_unlock(&once_control->lock);
+    }
 
-  pthread_mutex_unlock(&THR_LOCK_once);
   return 0;
 }
 

src/pthread.h

@@ -10,6 +10,14 @@
 extern "C" {
 #endif
 
+/*
+ * Boolean values to make us independent of system includes.
+ */
+enum {
+  PTW32_FALSE = 0,
+  PTW32_TRUE = (! PTW32_FALSE)
+};
+
 /*
  * Flags for once initialization.
  */
@@ -85,10 +93,6 @@ void  pthread_setprio( int, int);
 #define pthread_condattr_init(A) 	0
 #define pthread_condattr_destroy(A)	0
 
-typedef int* pthread_once_t;
-#define PTHREAD_ONCE_INIT ((pthread_once_t)-1)
-int pthread_once(pthread_once_t *once_control, void (*init_routine)(void));
-
 int pthread_attr_getstacksize(const pthread_attr_t *attr, size_t *stacksize);
 int pthread_attr_setstacksize(pthread_attr_t *attr, size_t stacksize); 
 
@@ -206,6 +210,26 @@ int pthread_setcanceltype(int type, int *oldtype);
 void pthread_testcancel(void);
 int pthread_atfork(void (*prepare)(void), void (*parent)(void),void (*child)(void)); 
 
+/*
+ * ====================
+ * ====================
+ * Once Key
+ * ====================
+ * ====================
+ */
+#define PTHREAD_ONCE_INIT       { PTW32_FALSE, 0, 0, 0}
+
+struct pthread_once_t_
+{
+  unsigned        done;        /* indicates if user function has been executed */
+  pthread_mutex_t lock;
+  int          reserved1;
+  int          reserved2;
+};
+typedef struct pthread_once_t_ pthread_once_t;
+int pthread_once(pthread_once_t *once_control, void (*init_routine)(void));
+
+
 #ifdef __cplusplus
 } // extern "C"
 #endif