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, 11 insertions, 6 deletions

diff --git a/cpukit/score/src/coretodset.c b/cpukit/score/src/coretodset.c
index ff76581bbd..c265606137 100644
--- a/cpukit/score/src/coretodset.c
+++ b/cpukit/score/src/coretodset.c
@@ -23,12 +23,14 @@
 #include <rtems/score/watchdogimpl.h>
 
 void _TOD_Set_with_timestamp(
-  const Timestamp_Control *tod
+  const Timestamp_Control *tod_as_timestamp
 )
 {
-  uint32_t nanoseconds = _Timestamp_Get_nanoseconds( tod );
-  Watchdog_Interval seconds_next = _Timestamp_Get_seconds( tod );
+  TOD_Control *tod = &_TOD;
+  uint32_t nanoseconds = _Timestamp_Get_nanoseconds( tod_as_timestamp );
+  Watchdog_Interval seconds_next = _Timestamp_Get_seconds( tod_as_timestamp );
   Watchdog_Interval seconds_now;
+  ISR_Level level;
 
   _Thread_Disable_dispatch();
 
@@ -39,9 +41,12 @@ void _TOD_Set_with_timestamp(
   else
     _Watchdog_Adjust_seconds( WATCHDOG_FORWARD, seconds_next - seconds_now );
 
-  _TOD.now = *tod;
-  _TOD.seconds_trigger = nanoseconds;
-  _TOD.is_set = true;
+  _TOD_Acquire( tod, level );
+  tod->now = *tod_as_timestamp;
+  _TOD_Release( tod, level );
+
+  tod->seconds_trigger = nanoseconds;
+  tod->is_set = true;
 
   _Thread_Enable_dispatch();
 }