Changeset 834a86fe in rtems

Timestamp:

11/15/21 09:20:30 (9 months ago)

Author:

Sebastian Huber <sebastian.huber@…>

Branches:

master

Children:

cd791039

Parents:

c69a70a

git-author:

Sebastian Huber <sebastian.huber@…> (11/15/21 09:20:30)

git-committer:

Sebastian Huber <sebastian.huber@…> (11/23/21 10:00:28)

Message:

score: Restrict affinity for EDF SMP scheduler

The SMP EDF scheduler supports a one-to-one and one-to-all thread to
processor affinity. It accepted affinity sets which are a proper
subset of the online processor containing at least two processors owned by
the scheduler. In this case it used a one-to-one thread to processor
affinity. This leads to undefined behaviour if a processor is removed
since the higher level check in rtems_scheduler_remove_processor() does
not account for this implementation detail.

Restrict the affinity set accepted by the SMP EDF scheduler to

1. all online processors, or

2. exactly one processor owned by the scheduler.

Close #4545.

File:

• cpukit/score/src/scheduleredfsmp.c (modified) (1 diff)

cpukit/score/src/scheduleredfsmp.c

@@ -886 +886 @@
   Scheduler_Context      *context;
   Scheduler_EDF_SMP_Node *node;
-  Processor_mask          local_affinity;
   uint8_t                 rqi;
 
   context = _Scheduler_Get_context( scheduler );
-  _Processor_mask_And( &local_affinity, &context->Processors, affinity );
-
-  if ( _Processor_mask_Is_zero( &local_affinity ) ) {
-    return STATUS_INVALID_NUMBER;
-  }
+
+  /*
+   * We support a thread to processor affinity to all online processors and an
+   * affinity to exactly one processor.  This restriction is necessary to avoid
+   * issues if processors are added or removed to or from the scheduler.
+   */
 
   if ( _Processor_mask_Is_equal( affinity, &_SMP_Online_processors ) ) {
     rqi = 0;
   } else {
-    rqi = _Processor_mask_Find_last_set( &local_affinity );
+    Processor_mask local_affinity;
+    Processor_mask one_to_one;
+    uint32_t       last;
+
+    _Processor_mask_And( &local_affinity, &context->Processors, affinity );
+
+    if ( _Processor_mask_Is_zero( &local_affinity ) ) {
+      return STATUS_INVALID_NUMBER;
+    }
+
+    last = _Processor_mask_Find_last_set( affinity );
+    _Processor_mask_From_index( &one_to_one, last - 1 );
+
+    /*
+     * Use the global affinity set and not the affinity set local to the
+     * scheduler to check for a one-to-one affinity.
+     */
+    if ( !_Processor_mask_Is_equal( &one_to_one, affinity ) ) {
+      return STATUS_INVALID_NUMBER;
+    }
+
+    rqi = last;
   }