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.

1 files changed, 6 insertions, 1 deletions

diff --git a/cpukit/libmisc/cpuuse/cpuusagereset.c b/cpukit/libmisc/cpuuse/cpuusagereset.c
index 8e9fe54ced..6ef50f9b25 100644
--- a/cpukit/libmisc/cpuuse/cpuusagereset.c
+++ b/cpukit/libmisc/cpuuse/cpuusagereset.c
@@ -21,13 +21,18 @@
 #include <rtems/cpuuse.h>
 #include <rtems/score/percpu.h>
 #include <rtems/score/todimpl.h>
+#include <rtems/score/schedulerimpl.h>
 #include <rtems/score/watchdogimpl.h>
 
 static void CPU_usage_Per_thread_handler(
   Thread_Control *the_thread
 )
 {
+  ISR_lock_Context lock_context;
+
+  _Scheduler_Acquire( the_thread, &lock_context );
   _Timestamp_Set_to_zero( &the_thread->cpu_time_used );
+  _Scheduler_Release( the_thread, &lock_context );
 }
 
 /*
@@ -44,7 +49,7 @@ void rtems_cpu_usage_reset( void )
   for ( cpu_index = 0 ; cpu_index < cpu_count ; ++cpu_index ) {
     Per_CPU_Control *cpu = _Per_CPU_Get_by_index( cpu_index );
 
-    cpu->time_of_last_context_switch = CPU_usage_Uptime_at_last_reset;
+    cpu->cpu_usage_timestamp = CPU_usage_Uptime_at_last_reset;
   }
 
   rtems_iterate_over_all_threads(CPU_usage_Per_thread_handler);