score: Use an ISR lock for TOD

Two issues are addressed.

1. On single processor configurations the set/get of the now/uptime
timestamps is now consistently protected by ISR disable/enable
sequences.  Previously nested interrupts could observe partially written
values since 64-bit writes are not atomic on 32-bit architectures in
general.  This could lead to non-monotonic uptime timestamps.

2. The TOD now/uptime maintanence is now independent of the giant lock.
This is the first step to remove the giant lock in _Thread_Dispatch().

1 files changed, 32 insertions, 0 deletions

diff --git a/cpukit/score/src/coretodsecondssinceepoch.c b/cpukit/score/src/coretodsecondssinceepoch.c
new file mode 100644
index 0000000000..91445c0c80
--- /dev/null
+++ b/cpukit/score/src/coretodsecondssinceepoch.c
@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2013 embedded brains GmbH.  All rights reserved.
+ *
+ *  embedded brains GmbH
+ *  Dornierstr. 4
+ *  82178 Puchheim
+ *  Germany
+ *  <rtems@embedded-brains.de>
+ *
+ * The license and distribution terms for this file may be
+ * found in the file LICENSE in this distribution or at
+ * http://www.rtems.com/license/LICENSE.
+ */
+
+#if HAVE_CONFIG_H
+  #include "config.h"
+#endif
+
+#include <rtems/score/todimpl.h>
+
+uint32_t _TOD_Seconds_since_epoch( void )
+{
+  TOD_Control      *tod = &_TOD;
+  ISR_Level         level;
+  Timestamp_Control now;
+
+  _TOD_Acquire( tod, level );
+   now = tod->now;
+  _TOD_Release( tod, level );
+
+  return _Timestamp_Get_seconds( &now );
+}