score: Fix CPU time used by executing threads

The CPU time used of a thread was previously maintained per-processor
mostly during _Thread_Dispatch().  However, on SMP configurations the
actual processor of a thread is difficult to figure out since thread
dispatching is a highly asynchronous process (e.g. via inter-processor
interrupts).  Only the intended processor of a thread is known to the
scheduler easily.  Do the CPU usage accounting during thread heir
updates in the context of the scheduler operations.  Provide the
function _Thread_Get_CPU_time_used() to get the CPU usage of a thread
using proper locks to get a consistent value.

Close #2627.

3 files changed, 48 insertions, 5 deletions

diff --git a/cpukit/score/src/schedulersmpstartidle.c b/cpukit/score/src/schedulersmpstartidle.c
index de125d3323..0ffb628550 100644
--- a/cpukit/score/src/schedulersmpstartidle.c
+++ b/cpukit/score/src/schedulersmpstartidle.c
@@ -22,6 +22,7 @@ void _Scheduler_SMP_Start_idle(
   Scheduler_SMP_Context *self = _Scheduler_SMP_Get_self( context );
   Scheduler_SMP_Node *node = _Scheduler_SMP_Thread_get_node( thread );
 
+  _Scheduler_Thread_change_state( thread, THREAD_SCHEDULER_SCHEDULED );
   node->state = SCHEDULER_SMP_NODE_SCHEDULED;
 
   _Thread_Set_CPU( thread, cpu );
diff --git a/cpukit/score/src/threaddispatch.c b/cpukit/score/src/threaddispatch.c
index 1b36c93fbb..ce5d118a22 100644
--- a/cpukit/score/src/threaddispatch.c
+++ b/cpukit/score/src/threaddispatch.c
@@ -108,11 +108,6 @@ void _Thread_Do_dispatch( Per_CPU_Control *cpu_self, ISR_Level level )
     _ISR_Enable( level );
 #endif
 
-    _Thread_Update_cpu_time_used(
-      executing,
-      &cpu_self->time_of_last_context_switch
-    );
-
     _User_extensions_Thread_switch( executing, heir );
     _Thread_Save_fp( executing );
     _Context_Switch( &executing->Registers, &heir->Registers );
diff --git a/cpukit/score/src/threadgetcputimeused.c b/cpukit/score/src/threadgetcputimeused.c
new file mode 100644
index 0000000000..6bfe8ea216
--- /dev/null
+++ b/cpukit/score/src/threadgetcputimeused.c
@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2016 embedded brains GmbH.  All rights reserved.
+ *
+ *  embedded brains GmbH
+ *  Dornierstr. 4
+ *  82178 Puchheim
+ *  Germany
+ *  <rtems@embedded-brains.de>
+ *
+ * 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/threadimpl.h>
+#include <rtems/score/schedulerimpl.h>
+
+static bool _Thread_Is_scheduled( const Thread_Control *the_thread )
+{
+#if defined(RTEMS_SMP)
+  return the_thread->Scheduler.state == THREAD_SCHEDULER_SCHEDULED;
+#else
+  return _Thread_Is_executing( the_thread );
+#endif
+}
+
+void _Thread_Get_CPU_time_used(
+  Thread_Control    *the_thread,
+  Timestamp_Control *cpu_time_used
+)
+{
+  ISR_lock_Context lock_context;
+
+  _Scheduler_Acquire( the_thread, &lock_context );
+
+  if ( _Thread_Is_scheduled( the_thread ) ) {
+    _Thread_Update_CPU_time_used( the_thread, _Thread_Get_CPU( the_thread ) );
+  }
+
+  *cpu_time_used = the_thread->cpu_time_used;
+
+  _Scheduler_Release( the_thread, &lock_context );
+}