Ticket #430: watchdog.diff1

This patch addresses the following issues:

 - _Watchdog_Ticks_since_boot should be a VOLATILE variable.
 - _Watchdog_Sync_count++ should be protected by _ISR_Disable
   (prevent corruption in case ISR calls watchdoginsert)
 - 'restart' algorithm needs to enforce reloading the list
   head in case a TICK interrupt during ISR_Flash()  modified the list.
   This is achieved by a proper VOLATILE cast.

NOTE: PowerPC BSPs using the new exception processing MUST BE UPDATED
      to maintain _ISR_Nest_level. See also PR288 which provides fixes
      for the affected BSPs distributed with RTEMS.

Till Straumann <strauman@slac.stanford.edu>, 2003/7

Index: cpukit/score/include/rtems/score/watchdog.h
===================================================================
RCS file: /afs/slac/g/spear/cvsrep/rtems/src-20030128/cpukit/score/include/rtems/score/watchdog.h,v
retrieving revision 1.1.1.3
retrieving revision 1.2
diff -c -r1.1.1.3 -r1.2
*** cpukit/score/include/rtems/score/watchdog.h 29 Jan 2003 22:59:29 -0000      1.1.1.3
--- cpukit/score/include/rtems/score/watchdog.h 12 Jul 2003 05:33:56 -0000      1.2
***************
*** 103,109 ****
   *  system was booted.
   */
  
! SCORE_EXTERN Watchdog_Interval _Watchdog_Ticks_since_boot;
  
  /*
   *  The following defines the watchdog chains which are managed
--- 103,109 ----
   *  system was booted.
   */
  
! SCORE_EXTERN volatile Watchdog_Interval _Watchdog_Ticks_since_boot;
  
  /*
   *  The following defines the watchdog chains which are managed
Index: cpukit/score/src/watchdoginsert.c
===================================================================
RCS file: /afs/slac/g/spear/cvsrep/rtems/src-20030128/cpukit/score/src/watchdoginsert.c,v
retrieving revision 1.1.1.2
retrieving revision 1.2
diff -c -r1.1.1.2 -r1.2
*** cpukit/score/src/watchdoginsert.c   29 Jan 2003 22:59:25 -0000      1.1.1.2
--- cpukit/score/src/watchdoginsert.c   12 Jul 2003 05:35:52 -0000      1.2
***************
*** 38,50 ****
    insert_isr_nest_level   = _ISR_Nest_level;
    the_watchdog->state = WATCHDOG_BEING_INSERTED;
  
    _Watchdog_Sync_count++;
  restart:
    delta_interval = the_watchdog->initial;
  
!   _ISR_Disable( level );
! 
!   for ( after = _Watchdog_First( header ) ;
          ;
          after = _Watchdog_Next( after ) ) {
  
--- 38,65 ----
    insert_isr_nest_level   = _ISR_Nest_level;
    the_watchdog->state = WATCHDOG_BEING_INSERTED;
  
+   _ISR_Disable( level );
+ 
    _Watchdog_Sync_count++;
+ 
  restart:
    delta_interval = the_watchdog->initial;
  
!   /*
!    * We CANT use _Watchdog_First() here, because a TICK interrupt
!    * could modify the chain during the _ISR_Flash() below. Hence,
!    * the header is pointing to volatile data. The _Watchdog_First()
!    * INLINE routine (but not the macro - note the subtle difference)
!    * casts away the 'volatile'...
!    *
!    * Also, this is only necessary because we call no other routine
!    * from this piece of code, hence the compiler thinks it's safe to
!    * cache *header!!
!    *
!    *  Till Straumann, 7/2003 (gcc-3.2.2 -O4 on powerpc)
!    *
!    */
!   for ( after = (Watchdog_Control *) ((volatile Chain_Control *)header)->first ;
          ;
          after = _Watchdog_Next( after ) ) {
  
***************
*** 75,81 ****
  
       if ( _Watchdog_Sync_level > insert_isr_nest_level ) {
         _Watchdog_Sync_level = insert_isr_nest_level;
-        _ISR_Enable( level );
         goto restart;
       }
    }
--- 90,95 ----