Changeset cfc257fc in rtems

Timestamp:

Jul 18, 2003, 2:47:36 PM (18 years ago)

Author:

Joel Sherrill <joel.sherrill@…>

Children:

367a0e2

Parents:

8f51fa52

Message:

2003-07-18 Till Straumann <strauman@…>

PR 430/rtems

• include/rtems/score/watchdog.h: _Watchdog_Ticks_since_boot should be a VOLATILE variable.
• src/watchdoginsert.c: '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. Also _Watchdog_Sync_count++ should be protected by _ISR_Disable (prevent corruption in case ISR calls watchdoginsert)
• src/watchdogadjust.c: ISR protection added.
• src/watchdogtickle.c: ISR protection added. 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.

Location:

cpukit/score

Files:

• ChangeLog (modified) (1 diff)
• include/rtems/score/watchdog.h (modified) (1 diff)
• src/watchdogadjust.c (modified) (3 diffs)
• src/watchdoginsert.c (modified) (2 diffs)
• src/watchdogtickle.c (modified) (2 diffs)

cpukit/score/ChangeLog

@@ +1 @@
+2003-07-18      Till Straumann <strauman@slac.stanford.edu>
+
+        PR 430/rtems
+        * include/rtems/score/watchdog.h: _Watchdog_Ticks_since_boot should
+        be a VOLATILE variable.
+        * src/watchdoginsert.c: '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.
+        Also _Watchdog_Sync_count++ should be protected by _ISR_Disable
+        (prevent corruption in case ISR calls watchdoginsert)
+        * src/watchdogadjust.c: ISR protection added.
+        * src/watchdogtickle.c: ISR protection added.
+        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.
+
 2003-07-07      Joel Sherrill <joel@OARcorp.com>
 

cpukit/score/include/rtems/score/watchdog.h

@@ -104 +104 @@
  */
 
-SCORE_EXTERN Watchdog_Interval _Watchdog_Ticks_since_boot;
+SCORE_EXTERN volatile Watchdog_Interval _Watchdog_Ticks_since_boot;
 
 /*

cpukit/score/src/watchdogadjust.c

@@ -38 +38 @@
 )
 {
+  ISR_Level level;
+
+  _ISR_Disable( level );
+
+  /*
+   * NOTE: It is safe NOT to make 'header' a pointer
+   *       to volatile data (contrast this with watchdoginsert.c)
+   *       because we call _Watchdog_Tickle() below and
+   *       hence the compiler must not assume *header to remain
+   *       unmodified across that call.
+   *
+   *       Till Straumann, 7/2003
+   */
   if ( !_Chain_Is_empty( header ) ) {
     switch ( direction ) {
@@ -51 +64 @@
             units -= _Watchdog_First( header )->delta_interval;
             _Watchdog_First( header )->delta_interval = 1;
+
+                        _ISR_Enable( level );
+
             _Watchdog_Tickle( header );
+
+                        _ISR_Disable( level );
+
             if ( _Chain_Is_empty( header ) )
               break;
@@ -59 +78 @@
     }
   }
+
+  _ISR_Enable( level );
+
 }
 

cpukit/score/src/watchdoginsert.c

@@ -39 +39 @@
   the_watchdog->state = WATCHDOG_BEING_INSERTED;
 
+  _ISR_Disable( level );
+
   _Watchdog_Sync_count++;
+
 restart:
   delta_interval = the_watchdog->initial;
 
-  _ISR_Disable( level );
-
-  for ( after = _Watchdog_First( header ) ;
+  /*
+   * 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 ) ) {
@@ -76 +91 @@
      if ( _Watchdog_Sync_level > insert_isr_nest_level ) {
        _Watchdog_Sync_level = insert_isr_nest_level;
-       _ISR_Enable( level );
        goto restart;
      }

cpukit/score/src/watchdogtickle.c

@@ -34 +34 @@
 )
 {
+  ISR_Level level;
   Watchdog_Control *the_watchdog;
+  Watchdog_States  watchdog_state;
+
+  /*
+   * See the comment in watchdoginsert.c and watchdogadjust.c
+   * about why it's safe not to declare header a pointer to 
+   * volatile data - till, 2003/7
+   */
+
+  _ISR_Disable( level );
 
   if ( _Chain_Is_empty( header ) )
-    return;
+    goto leave;
 
   the_watchdog = _Watchdog_First( header );
   the_watchdog->delta_interval--;
   if ( the_watchdog->delta_interval != 0 )
-    return;
+    goto leave;
 
   do {
-     switch( _Watchdog_Remove( the_watchdog ) ) {
+         watchdog_state = _Watchdog_Remove( the_watchdog );
+
+         _ISR_Enable( level );
+
+     switch( watchdog_state ) {
        case WATCHDOG_ACTIVE:
          (*the_watchdog->routine)(
@@ -72 +86 @@
          break;
      }
+
+         _ISR_Disable( level );
+
      the_watchdog = _Watchdog_First( header );
    } while ( !_Chain_Is_empty( header ) &&
              (the_watchdog->delta_interval == 0) );
+
+leave:
+   _ISR_Enable(level);
 }