score: Add Watchdog_Iterator

Rewrite the _Watchdog_Insert(), _Watchdog_Remove() and
_Watchdog_Tickle() functions to use iterator items to synchronize
concurrent operations.  This makes it possible to get rid of the global
variables _Watchdog_Sync_level and _Watchdog_Sync_count which are a
blocking point for scalable SMP solutions.

Update #2307.

1 files changed, 64 insertions, 48 deletions

diff --git a/cpukit/score/src/watchdoginsert.c b/cpukit/score/src/watchdoginsert.c
index 0ad59ff61a..6d2df8222f 100644
--- a/cpukit/score/src/watchdoginsert.c
+++ b/cpukit/score/src/watchdoginsert.c
@@ -19,76 +19,92 @@
 #endif
 
 #include <rtems/score/watchdogimpl.h>
-#include <rtems/score/isrlevel.h>
-#include <rtems/score/percpu.h>
 
-void _Watchdog_Insert(
-  Watchdog_Header       *header,
-  Watchdog_Control      *the_watchdog
+static void _Watchdog_Insert_fixup(
+  Watchdog_Header   *header,
+  Watchdog_Control  *next_watchdog,
+  Watchdog_Interval  delta
 )
 {
-  ISR_lock_Context   lock_context;
-  Watchdog_Control  *after;
-  uint32_t           insert_isr_nest_level;
-  Watchdog_Interval  delta_interval;
+  const Chain_Node *iterator_tail;
+  Chain_Node       *iterator_node;
 
+  next_watchdog->delta_interval -= delta;
 
-  insert_isr_nest_level   = _ISR_Nest_level;
+  iterator_node = _Chain_First( &header->Iterators );
+  iterator_tail = _Chain_Immutable_tail( &header->Iterators );
 
-  _Watchdog_Acquire( header, &lock_context );
+  while ( iterator_node != iterator_tail ) {
+    Watchdog_Iterator *iterator;
 
-  /*
-   *  Check to see if the watchdog has just been inserted by a
-   *  higher priority interrupt.  If so, abandon this insert.
-   */
+    iterator = (Watchdog_Iterator *) iterator_node;
 
-  if ( the_watchdog->state != WATCHDOG_INACTIVE ) {
-    _Watchdog_Release( header, &lock_context );
-    return;
+    if ( iterator->current == &next_watchdog->Node ) {
+      iterator->delta_interval -= delta;
+    }
+
+    iterator_node = _Chain_Next( iterator_node );
   }
+}
 
-  the_watchdog->state = WATCHDOG_BEING_INSERTED;
-  _Watchdog_Sync_count++;
+void _Watchdog_Insert(
+  Watchdog_Header  *header,
+  Watchdog_Control *the_watchdog
+)
+{
+  ISR_lock_Context lock_context;
 
-restart:
-  delta_interval = the_watchdog->initial;
+  _Watchdog_Acquire( header, &lock_context );
 
-  for ( after = _Watchdog_First( header ) ;
-        ;
-        after = _Watchdog_Next( after ) ) {
+  if ( the_watchdog->state == WATCHDOG_INACTIVE ) {
+    Watchdog_Iterator  iterator;
+    Chain_Node        *current;
+    Chain_Node        *next;
+    Watchdog_Interval  delta;
 
-     if ( delta_interval == 0 || !_Watchdog_Next( after ) )
-       break;
+    the_watchdog->state = WATCHDOG_BEING_INSERTED;
 
-     if ( delta_interval < after->delta_interval ) {
-       after->delta_interval -= delta_interval;
-       break;
-     }
+    _Chain_Append_unprotected( &header->Iterators, &iterator.Node );
 
-     delta_interval -= after->delta_interval;
+    delta = the_watchdog->initial;
+    current = _Chain_Head( &header->Watchdogs );
 
-     _Watchdog_Flash( header, &lock_context );
+    while (
+      ( next = _Chain_Next( current ) ) != _Chain_Tail( &header->Watchdogs )
+    ) {
+      Watchdog_Control  *next_watchdog;
+      Watchdog_Interval  delta_next;
 
-     if ( the_watchdog->state != WATCHDOG_BEING_INSERTED ) {
-       goto exit_insert;
-     }
+      next_watchdog = (Watchdog_Control *) next;
+      delta_next = next_watchdog->delta_interval;
 
-     if ( _Watchdog_Sync_level > insert_isr_nest_level ) {
-       _Watchdog_Sync_level = insert_isr_nest_level;
-       goto restart;
-     }
-  }
+      if ( delta < delta_next ) {
+        _Watchdog_Insert_fixup( header, next_watchdog, delta );
+        break;
+      }
+
+      iterator.delta_interval = delta - delta_next;
+      iterator.current = next;
 
-  _Watchdog_Activate( the_watchdog );
+      _Watchdog_Flash( header, &lock_context );
 
-  the_watchdog->delta_interval = delta_interval;
+      if ( the_watchdog->state != WATCHDOG_BEING_INSERTED ) {
+        goto abort_insert;
+      }
 
-  _Chain_Insert_unprotected( after->Node.previous, &the_watchdog->Node );
+      delta = iterator.delta_interval;
+      current = iterator.current;
+    }
 
-  the_watchdog->start_time = _Watchdog_Ticks_since_boot;
+    the_watchdog->delta_interval = delta;
+    the_watchdog->start_time = _Watchdog_Ticks_since_boot;
+    _Watchdog_Activate( the_watchdog );
+    _Chain_Insert_unprotected( current, &the_watchdog->Node );
+
+abort_insert:
+
+    _Chain_Extract_unprotected( &iterator.Node );
+  }
 
-exit_insert:
-  _Watchdog_Sync_level = insert_isr_nest_level;
-  _Watchdog_Sync_count--;
   _Watchdog_Release( header, &lock_context );
 }