3 files changed, 61 insertions, 14 deletions

diff --git a/cpukit/include/rtems/rtems/tasks.h b/cpukit/include/rtems/rtems/tasks.h
index 0392586759..8e87bfd14a 100644
--- a/cpukit/include/rtems/rtems/tasks.h
+++ b/cpukit/include/rtems/rtems/tasks.h
@@ -867,9 +867,12 @@ rtems_status_code rtems_scheduler_add_processor(
  *
  * @retval ::RTEMS_INVALID_NUMBER The processor was not owned by the scheduler.
  *
- * @retval ::RTEMS_RESOURCE_IN_USE The set of processors owned by the scheduler
- *   would have been empty after the processor removal and there was at least
- *   one non-idle task that used this scheduler as its home scheduler.
+ * @retval ::RTEMS_RESOURCE_IN_USE The processor was required by at least one
+ *   non-idle task that used the scheduler as its home scheduler.
+ *
+ * @retval ::RTEMS_RESOURCE_IN_USE The processor was the last processor owned
+ *   by the scheduler and there was at least one task that used the scheduler
+ *   as a helping scheduler.
  *
  * @par Notes
  * Removing a processor from a scheduler is a complex operation that involves
diff --git a/cpukit/include/rtems/score/schedulersmpimpl.h b/cpukit/include/rtems/score/schedulersmpimpl.h
index 97a77121ed..c37f53c8c0 100644
--- a/cpukit/include/rtems/score/schedulersmpimpl.h
+++ b/cpukit/include/rtems/score/schedulersmpimpl.h
@@ -1978,8 +1978,9 @@ static inline Thread_Control *_Scheduler_SMP_Remove_processor(
   victim_owner = _Scheduler_Node_get_owner( victim_node );
 
   if ( !victim_owner->is_idle ) {
-    Thread_Control *victim_idle;
-    Scheduler_Node *idle_node;
+    Thread_Control  *victim_idle;
+    Scheduler_Node  *idle_node;
+    Priority_Control insert_priority;
 
     victim_idle = _Scheduler_Release_idle_thread_if_necessary(
       victim_node,
@@ -1996,13 +1997,10 @@ static inline Thread_Control *_Scheduler_SMP_Remove_processor(
       _Scheduler_SMP_Allocate_processor_exact
     );
 
-    if ( !_Chain_Is_empty( &self->Scheduled ) ) {
-      Priority_Control insert_priority;
-
-      insert_priority = _Scheduler_SMP_Node_priority( victim_node );
-      insert_priority = SCHEDULER_PRIORITY_APPEND( insert_priority );
-      ( *enqueue )( &self->Base, victim_node, insert_priority );
-    }
+    _Assert( !_Chain_Is_empty( &self->Scheduled ) );
+    insert_priority = _Scheduler_SMP_Node_priority( victim_node );
+    insert_priority = SCHEDULER_PRIORITY_APPEND( insert_priority );
+    ( *enqueue )( &self->Base, victim_node, insert_priority );
   } else {
     _Assert( victim_owner == victim_user );
     _Assert( _Scheduler_Node_get_idle( victim_node ) == NULL );
diff --git a/cpukit/rtems/src/schedulerremoveprocessor.c b/cpukit/rtems/src/schedulerremoveprocessor.c
index 79c17bda49..3136a8e0c0 100644
--- a/cpukit/rtems/src/schedulerremoveprocessor.c
+++ b/cpukit/rtems/src/schedulerremoveprocessor.c
@@ -35,7 +35,7 @@ typedef struct {
   rtems_status_code        status;
 } Scheduler_Processor_removal_context;
 
-static bool _Scheduler_Check_processor_removal(
+static bool _Scheduler_Check_processor_not_required(
   Thread_Control *the_thread,
   void           *arg
 )
@@ -68,6 +68,45 @@ static bool _Scheduler_Check_processor_removal(
   _Thread_Wait_release( the_thread, &queue_context );
   return iter_context->status != RTEMS_SUCCESSFUL;
 }
+
+static bool _Scheduler_Check_no_helping(
+  Thread_Control *the_thread,
+  void           *arg
+)
+{
+  Scheduler_Processor_removal_context *iter_context;
+  ISR_lock_Context                     lock_context;
+  const Chain_Node                    *node;
+  const Chain_Node                    *tail;
+
+  if ( the_thread->is_idle ) {
+    return false;
+  }
+
+  iter_context = arg;
+
+  _Thread_State_acquire( the_thread, &lock_context );
+  node = _Chain_Immutable_first( &the_thread->Scheduler.Scheduler_nodes );
+  tail = _Chain_Immutable_tail( &the_thread->Scheduler.Scheduler_nodes );
+
+  do {
+    const Scheduler_Node    *scheduler_node;
+    const Scheduler_Control *scheduler;
+
+    scheduler_node = SCHEDULER_NODE_OF_THREAD_SCHEDULER_NODE( node );
+    scheduler = _Scheduler_Node_get_scheduler( scheduler_node );
+
+    if ( scheduler == iter_context->scheduler ) {
+      iter_context->status = RTEMS_RESOURCE_IN_USE;
+      break;
+    }
+
+    node = _Chain_Immutable_next( node );
+  } while ( node != tail );
+
+  _Thread_State_release( the_thread, &lock_context );
+  return iter_context->status != RTEMS_SUCCESSFUL;
+}
 #endif
 
 rtems_status_code rtems_scheduler_remove_processor(
@@ -116,7 +155,14 @@ rtems_status_code rtems_scheduler_remove_processor(
   _Scheduler_Release_critical( scheduler, &lock_context );
   _ISR_lock_ISR_enable( &lock_context );
 
-  _Thread_Iterate( _Scheduler_Check_processor_removal, &iter_context );
+  _Thread_Iterate( _Scheduler_Check_processor_not_required, &iter_context );
+
+  if (
+    _Processor_mask_Is_zero( &scheduler_context->Processors ) &&
+    iter_context.status == RTEMS_SUCCESSFUL
+  ) {
+    _Thread_Iterate( _Scheduler_Check_no_helping, &iter_context );
+  }
 
   _ISR_lock_ISR_disable( &lock_context );
   _Scheduler_Acquire_critical( scheduler, &lock_context );