empty G_ATOMIC_MEMORY_BARRIER() definition for !G_THREADS_ENABLED

2004-02-26  Sebastian Wilhelmi  <seppi@seppi.de>

	* glib/gatomic.h: empty G_ATOMIC_MEMORY_BARRIER() definition for
	!G_THREADS_ENABLED

	* glib/gthread.h: Define g_once and
	g_static_mutex_get_mutex_impl_shortcut in terms of
	G_MEMORY_BARRIER, if defined and if we can inline.

	* configure.in: Remove double checked locking feature check.

ChangeLog

@@ -1,5 +1,14 @@
 2004-02-26  Sebastian Wilhelmi  <seppi@seppi.de>
 
+	* glib/gatomic.h: empty G_ATOMIC_MEMORY_BARRIER() definition for
+	!G_THREADS_ENABLED
+
+	* glib/gthread.h: Define g_once and
+	g_static_mutex_get_mutex_impl_shortcut in terms of
+	G_MEMORY_BARRIER, if defined and if we can inline.
+
+	* configure.in: Remove double checked locking feature check.
+
 	* configure.in, config.h.win32.in, glib/gthread.c: Removed the PID
 	niceness surrogate for thread priorities as requested by Tim. It
 	does more harm than good.

ChangeLog.pre-2-10

@@ -1,5 +1,14 @@
 2004-02-26  Sebastian Wilhelmi  <seppi@seppi.de>
 
+	* glib/gatomic.h: empty G_ATOMIC_MEMORY_BARRIER() definition for
+	!G_THREADS_ENABLED
+
+	* glib/gthread.h: Define g_once and
+	g_static_mutex_get_mutex_impl_shortcut in terms of
+	G_MEMORY_BARRIER, if defined and if we can inline.
+
+	* configure.in: Remove double checked locking feature check.
+
 	* configure.in, config.h.win32.in, glib/gthread.c: Removed the PID
 	niceness surrogate for thread priorities as requested by Tim. It
 	does more harm than good.

ChangeLog.pre-2-12

@@ -1,5 +1,14 @@
 2004-02-26  Sebastian Wilhelmi  <seppi@seppi.de>
 
+	* glib/gatomic.h: empty G_ATOMIC_MEMORY_BARRIER() definition for
+	!G_THREADS_ENABLED
+
+	* glib/gthread.h: Define g_once and
+	g_static_mutex_get_mutex_impl_shortcut in terms of
+	G_MEMORY_BARRIER, if defined and if we can inline.
+
+	* configure.in: Remove double checked locking feature check.
+
 	* configure.in, config.h.win32.in, glib/gthread.c: Removed the PID
 	niceness surrogate for thread priorities as requested by Tim. It
 	does more harm than good.

ChangeLog.pre-2-4

@@ -1,5 +1,14 @@
 2004-02-26  Sebastian Wilhelmi  <seppi@seppi.de>
 
+	* glib/gatomic.h: empty G_ATOMIC_MEMORY_BARRIER() definition for
+	!G_THREADS_ENABLED
+
+	* glib/gthread.h: Define g_once and
+	g_static_mutex_get_mutex_impl_shortcut in terms of
+	G_MEMORY_BARRIER, if defined and if we can inline.
+
+	* configure.in: Remove double checked locking feature check.
+
 	* configure.in, config.h.win32.in, glib/gthread.c: Removed the PID
 	niceness surrogate for thread priorities as requested by Tim. It
 	does more harm than good.

ChangeLog.pre-2-6

@@ -1,5 +1,14 @@
 2004-02-26  Sebastian Wilhelmi  <seppi@seppi.de>
 
+	* glib/gatomic.h: empty G_ATOMIC_MEMORY_BARRIER() definition for
+	!G_THREADS_ENABLED
+
+	* glib/gthread.h: Define g_once and
+	g_static_mutex_get_mutex_impl_shortcut in terms of
+	G_MEMORY_BARRIER, if defined and if we can inline.
+
+	* configure.in: Remove double checked locking feature check.
+
 	* configure.in, config.h.win32.in, glib/gthread.c: Removed the PID
 	niceness surrogate for thread priorities as requested by Tim. It
 	does more harm than good.

ChangeLog.pre-2-8

@@ -1,5 +1,14 @@
 2004-02-26  Sebastian Wilhelmi  <seppi@seppi.de>
 
+	* glib/gatomic.h: empty G_ATOMIC_MEMORY_BARRIER() definition for
+	!G_THREADS_ENABLED
+
+	* glib/gthread.h: Define g_once and
+	g_static_mutex_get_mutex_impl_shortcut in terms of
+	G_MEMORY_BARRIER, if defined and if we can inline.
+
+	* configure.in: Remove double checked locking feature check.
+
 	* configure.in, config.h.win32.in, glib/gthread.c: Removed the PID
 	niceness surrogate for thread priorities as requested by Tim. It
 	does more harm than good.

configure.in

@@ -1188,27 +1188,6 @@ esac
 AC_MSG_RESULT($GIO)
 AC_SUBST(GIO)
 
-dnl check for cpu to enable double checked locking when possible
-dnl ************************************************************
-
-if test x"$have_threads" != xno; then
-	AC_MSG_CHECKING(whether double checked locking is safe)
-	# According to glibc/linuxthreads the following platforms do
-	# not have the notion of a read or write memory barrier and
-	# therefore the double checked locking should be safe. Have a
-	# look at pthread_once in glibc/linuxthreads/mutex.c to see,
-	# what this means.
-	case $host_cpu in
-		arm|hppa|i386|i686|ia64|m68k|sh|cris|x86_64)
-			g_use_double_checked_locking=yes
-		;;
-		*)
-			g_use_double_checked_locking=no
-		;;
-	esac
-	AC_MSG_RESULT($g_use_double_checked_locking)
-fi
-
 dnl ****************************************
 dnl *** platform dependent source checks ***
 dnl ****************************************
@@ -2233,24 +2212,6 @@ typedef struct _GMutex* GStaticMutex;
 _______EOF
 	fi
 
-	if test x$g_use_double_checked_locking = xyes; then
-		cat >>$outfile <<_______EOF
-/* double checked locking can be used on this platform */
-#define g_once(once, func, arg) \\
-  ((once)->status == G_ONCE_STATUS_READY ? (once)->retval : \\
-   g_once_impl (once, func, arg))
-#define g_static_mutex_get_mutex_impl_shortcut(mutex) \\
-  (*(mutex) ? *(mutex) : g_static_mutex_get_mutex_impl (mutex))
-_______EOF
-	else
-		cat >>$outfile <<_______EOF
-/* double checked locking is unsafe to use on this platform, do full locking */
-#define g_once(once, func, arg) (g_once_impl(once, func, arg))
-#define g_static_mutex_get_mutex_impl_shortcut(mutex) \\
-  (g_static_mutex_get_mutex_impl (mutex))
-_______EOF
-fi		
-
 	cat >>$outfile <<_______EOF
 /* This represents a system thread as used by the implementation. An
  * alien implementaion, as loaded by g_thread_init can only count on
@@ -2565,7 +2526,6 @@ xno)	g_enable_threads_def="#undef";;
 esac
 
 g_threads_impl_def=$g_threads_impl
-g_use_double_checked_locking=$g_use_double_checked_locking
 
 g_mutex_has_default="$mutex_has_default"
 g_mutex_sizeof="$glib_cv_sizeof_gmutex"

glib/gatomic.h

@@ -341,7 +341,7 @@ g_atomic_pointer_compare_and_exchange (gpointer *atomic,
   return result == oldval;
 }
 
-#     define  G_ATOMIC_MEMORY_BARRIER() /* Not needed */
+#     define G_ATOMIC_MEMORY_BARRIER() /* Not needed */
 
 #   elif defined(G_ATOMIC_INLINED_IMPLEMENTATION_POWERPC)
 /* Adapted from CVS version 1.12 of glibc's sysdeps/powerpc/bits/atomic.h 
@@ -450,7 +450,7 @@ g_atomic_pointer_compare_and_exchange (gpointer *atomic,
 #       error "Your system has an unsupported pointer size"
 #     endif /* GLIB_SIZEOF_VOID_P */
 
-#     define  G_ATOMIC_MEMORY_BARRIER() __asm ("sync" : : : "memory")
+#     define G_ATOMIC_MEMORY_BARRIER() __asm ("sync" : : : "memory")
 
 #   elif defined(G_ATOMIC_INLINED_IMPLEMENTATION_IA64)
 /* Adapted from CVS version 1.8 of glibc's sysdeps/ia64/bits/atomic.h
@@ -486,7 +486,7 @@ g_atomic_pointer_compare_and_exchange (gpointer *atomic,
 					  (long)oldval, (long)newval);
 }
 
-#     define  G_ATOMIC_MEMORY_BARRIER() __sync_synchronize ()
+#     define G_ATOMIC_MEMORY_BARRIER() __sync_synchronize ()
 
 #   else /* !G_ATOMIC_INLINED_IMPLEMENTATION_... */
 #     define G_ATOMIC_USE_FALLBACK_IMPLEMENTATION
@@ -503,6 +503,7 @@ gint32 g_atomic_int_exchange_and_add (gint32 *atomic, gint32  val);
   (*(atomic) == (oldval) ? (*(atomic) = (newval), TRUE) : FALSE)
 # define g_atomic_int_get(atomic) (*(atomic))
 # define g_atomic_pointer_get(atomic) (*(atomic))
+# define G_ATOMIC_MEMORY_BARRIER() /* Not needed */
 #endif /* G_THREADS_ENABLED */
 
 #ifdef G_ATOMIC_USE_FALLBACK_IMPLEMENTATION

glib/gthread.h

@@ -29,6 +29,8 @@
 
 #include <glib/gerror.h>
 #include <glib/gtypes.h>
+#include <glib/gutils.h>  /* for G_CAN_INLINE */
+#include <glib/gatomic.h>  /* for G_ATOMIC_MEMORY_BARRIER */
 
 G_BEGIN_DECLS
 
@@ -302,6 +304,30 @@ struct _GOnce
 
 gpointer g_once_impl (GOnce *once, GThreadFunc func, gpointer arg);
 
+#if defined (G_CAN_INLINE) && defined (G_ATOMIC_MEMORY_BARRIER)
+static inline gpointer 
+g_once (GOnce *once, GThreadFunc func, gpointer arg)
+{
+  if (once->status != G_ONCE_STATUS_READY)
+    return g_once_impl (once, func, arg);
+
+  G_ATOMIC_MEMORY_BARRIER ();
+  return once->retval;
+}
+static inline GMutex* 
+g_static_mutex_get_mutex_impl_shortcut (GMutex **mutex)
+{
+  if (! *mutex)
+    return g_static_mutex_get_mutex_impl (mutex);
+
+  G_ATOMIC_MEMORY_BARRIER ();
+  return *mutex;  
+}
+#else /* !G_CAN_INLINE || !G_ATOMIC_MEMORY_BARRIER */
+# define g_once g_once_impl
+# define g_static_mutex_get_mutex_impl_shortcut g_static_mutex_get_mutex_impl
+#endif /* G_CAN_INLINE && G_ATOMIC_MEMORY_BARRIER*/
+
 /* these are some convenience macros that expand to nothing if GLib
  * was configured with --disable-threads. for using StaticMutexes,
  * you define them with G_LOCK_DEFINE_STATIC (name) or G_LOCK_DEFINE (name)