1 files changed, 89 insertions, 0 deletions
diff --git a/ports/sysdeps/unix/sysv/linux/arm/nptl/pthread_once.c b/ports/sysdeps/unix/sysv/linux/arm/nptl/pthread_once.c
new file mode 100644
index 0000000000..0c03f1c816
--- /dev/null
+++ b/ports/sysdeps/unix/sysv/linux/arm/nptl/pthread_once.c
@@ -0,0 +1,89 @@
+/* Copyright (C) 2004-2012 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include "pthreadP.h"
+#include <lowlevellock.h>
+
+unsigned long int __fork_generation attribute_hidden;
+
+static void
+clear_once_control (void *arg)
+{
+  pthread_once_t *once_control = (pthread_once_t *) arg;
+
+  *once_control = 0;
+  lll_futex_wake (once_control, INT_MAX, LLL_PRIVATE);
+}
+
+int
+__pthread_once (pthread_once_t *once_control, void (*init_routine) (void))
+{
+  for (;;)
+    {
+      int oldval;
+      int newval;
+
+      /* Pseudo code:
+	 newval = __fork_generation | 1;
+	 oldval = *once_control;
+	 if ((oldval & 2) == 0)
+	   *once_control = newval;
+	 Do this atomically.
+      */
+      do
+	{
+	  newval = __fork_generation | 1;
+	  oldval = *once_control;
+	  if (oldval & 2)
+	    break;
+	} while (atomic_compare_and_exchange_val_acq (once_control, newval, oldval) != oldval);
+
+      /* Check if the initializer has already been done.  */
+      if ((oldval & 2) != 0)
+	return 0;
+
+      /* Check if another thread already runs the initializer.	*/
+      if ((oldval & 1) == 0)
+	break;
+
+      /* Check whether the initializer execution was interrupted by a fork.  */
+      if (oldval != newval)
+	break;
+
+      /* Same generation, some other thread was faster. Wait.  */
+      lll_futex_wait (once_control, oldval, LLL_PRIVATE);
+    }
+
+  /* This thread is the first here.  Do the initialization.
+     Register a cleanup handler so that in case the thread gets
+     interrupted the initialization can be restarted.  */
+  pthread_cleanup_push (clear_once_control, once_control);
+
+  init_routine ();
+
+  pthread_cleanup_pop (0);
+
+  /* Say that the initialisation is done.  */
+  *once_control = __fork_generation | 2;
+
+  /* Wake up all other threads.  */
+  lll_futex_wake (once_control, INT_MAX, LLL_PRIVATE);
+
+  return 0;
+}
+weak_alias (__pthread_once, pthread_once)
+hidden_def (__pthread_once)