score: Add clustered/partitioned scheduling

Clustered/partitioned scheduling helps to control the worst-case
latencies in the system.  The goal is to reduce the amount of shared
state in the system and thus prevention of lock contention.  Modern
multi-processor systems tend to have several layers of data and
instruction caches.  With clustered/partitioned scheduling it is
possible to honour the cache topology of a system and thus avoid
expensive cache synchronization traffic.

We have clustered scheduling in case the set of processors of a system
is partitioned into non-empty pairwise-disjoint subsets.  These subsets
are called clusters.  Clusters with a cardinality of one are partitions.
Each cluster is owned by exactly one scheduler instance.

1 files changed, 6 insertions, 2 deletions

diff --git a/cpukit/score/src/threadstart.c b/cpukit/score/src/threadstart.c
index b65a2c3380..dda9495a35 100644
--- a/cpukit/score/src/threadstart.c
+++ b/cpukit/score/src/threadstart.c
@@ -46,8 +46,12 @@ bool _Thread_Start(
     if ( cpu == NULL ) {
       _Thread_Ready( the_thread );
     } else {
-      the_thread->current_state = STATES_READY;
-      _Scheduler_Start_idle( _Scheduler_Get( the_thread ), the_thread, cpu );
+      const Scheduler_Control *scheduler = _Scheduler_Get_by_CPU( cpu );
+
+      if ( scheduler != NULL ) {
+        the_thread->current_state = STATES_READY;
+        _Scheduler_Start_idle( scheduler, the_thread, cpu );
+      }
     }
 
     _User_extensions_Thread_start( the_thread );