score: Fix scheduler yield in SMP configurations

Check that no ask help request is registered during unblock and yield
scheduler operations.  There is no need to ask for help if a scheduled
thread yields, since this is already covered by the pre-emption
detection.

Update #2556.

1 files changed, 38 insertions, 0 deletions

diff --git a/cpukit/score/src/schedulersmp.c b/cpukit/score/src/schedulersmp.c
new file mode 100644
index 0000000000..d68ac4fc8b
--- /dev/null
+++ b/cpukit/score/src/schedulersmp.c
@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2014, 2017 embedded brains GmbH.
+ *
+ * The license and distribution terms for this file may be
+ * found in the file LICENSE in this distribution or at
+ * http://www.rtems.org/license/LICENSE.
+ */
+
+#if HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <rtems/score/schedulersmpimpl.h>
+
+void _Scheduler_Request_ask_for_help( Thread_Control *the_thread )
+{
+  ISR_lock_Context lock_context;
+
+  _Thread_Scheduler_acquire_critical( the_thread, &lock_context );
+
+  if ( _Chain_Is_node_off_chain( &the_thread->Scheduler.Help_node ) ) {
+    Per_CPU_Control *cpu;
+
+    cpu = _Thread_Get_CPU( the_thread );
+    _Per_CPU_Acquire( cpu );
+
+    _Chain_Append_unprotected(
+      &cpu->Threads_in_need_for_help,
+      &the_thread->Scheduler.Help_node
+    );
+
+    _Per_CPU_Release( cpu );
+
+    _Thread_Dispatch_request( _Per_CPU_Get(), cpu );
+  }
+
+  _Thread_Scheduler_release_critical( the_thread, &lock_context );
+}