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, 27 insertions, 54 deletions

diff --git a/cpukit/libmisc/cpuuse/cpuusagereport.c b/cpukit/libmisc/cpuuse/cpuusagereport.c
index 98b5f8bfae..95d06480d6 100644
--- a/cpukit/libmisc/cpuuse/cpuusagereport.c
+++ b/cpukit/libmisc/cpuuse/cpuusagereport.c
@@ -44,7 +44,7 @@ void rtems_cpu_usage_report_with_plugin(
   Objects_Information *information;
   char                 name[13];
   uint32_t             ival, fval;
-  Timestamp_Control  uptime, total, ran, uptime_at_last_reset;
+  Timestamp_Control  uptime, total, used, uptime_at_last_reset;
   uint32_t seconds, nanoseconds;
 
   if ( !print )
@@ -90,38 +90,23 @@ void rtems_cpu_usage_report_with_plugin(
           name
         );
 
-        {
-          Timestamp_Control last;
-
-          /*
-           * If this is the currently executing thread, account for time
-           * since the last context switch.
-           */
-          ran = the_thread->cpu_time_used;
-          if ( _Thread_Get_time_of_last_context_switch( the_thread, &last ) ) {
-            Timestamp_Control used;
-            _TOD_Get_uptime( &uptime );
-            _Timestamp_Subtract( &last, &uptime, &used );
-            _Timestamp_Add_to( &ran, &used );
-          } else {
-            _TOD_Get_uptime( &uptime );
-          }
-          _Timestamp_Subtract( &uptime_at_last_reset, &uptime, &total );
-          _Timestamp_Divide( &ran, &total, &ival, &fval );
-
-          /*
-           * Print the information
-           */
-
-          seconds = _Timestamp_Get_seconds( &ran );
-          nanoseconds = _Timestamp_Get_nanoseconds( &ran ) /
-            TOD_NANOSECONDS_PER_MICROSECOND;
-          (*print)( context,
-            "%7" PRIu32 ".%06" PRIu32 " |%4" PRIu32 ".%03" PRIu32 "\n",
-            seconds, nanoseconds,
-            ival, fval
-          );
-        }
+        _Thread_Get_CPU_time_used( the_thread, &used );
+        _TOD_Get_uptime( &uptime );
+        _Timestamp_Subtract( &uptime_at_last_reset, &uptime, &total );
+        _Timestamp_Divide( &used, &total, &ival, &fval );
+
+        /*
+         * Print the information
+         */
+
+        seconds = _Timestamp_Get_seconds( &used );
+        nanoseconds = _Timestamp_Get_nanoseconds( &used ) /
+          TOD_NANOSECONDS_PER_MICROSECOND;
+        (*print)( context,
+          "%7" PRIu32 ".%06" PRIu32 " |%4" PRIu32 ".%03" PRIu32 "\n",
+          seconds, nanoseconds,
+          ival, fval
+        );
       }
     }
   }
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);
diff --git a/cpukit/libmisc/cpuuse/cpuusagetop.c b/cpukit/libmisc/cpuuse/cpuusagetop.c
index 6355e4e636..9b928588c7 100644
--- a/cpukit/libmisc/cpuuse/cpuusagetop.c
+++ b/cpukit/libmisc/cpuuse/cpuusagetop.c
@@ -218,12 +218,14 @@ static void
 task_usage(Thread_Control* thread, void* arg)
 {
   rtems_cpu_usage_data* data = (rtems_cpu_usage_data*) arg;
-  Timestamp_Control     usage = thread->cpu_time_used;
+  Timestamp_Control     usage;
   Timestamp_Control     current = data->zero;
   int                   j;
 
   data->stack_size += thread->Start.Initial_stack.size;
 
+  _Thread_Get_CPU_time_used(thread, &usage);
+
   for (j = 0; j < data->last_task_count; j++)
   {
     if (thread == data->last_tasks[j])
@@ -497,25 +499,6 @@ rtems_cpuusage_top_thread (rtems_task_argument arg)
       current_usage = data->current_usage[i];
 
       /*
-       * If this is the currently executing thread, account for time since
-       * the last context switch.
-       */
-      if (_Thread_Get_time_of_last_context_switch(thread, &last))
-      {
-        Timestamp_Control used;
-        Timestamp_Control now;
-
-        /*
-         * Get the current uptime and assume we are not pre-empted to
-         * measure the time from the last switch this thread and now.
-         */
-        _TOD_Get_uptime(&now);
-        _Timestamp_Subtract(&last, &now, &used);
-        _Timestamp_Add_to(&usage, &used);
-        _Timestamp_Add_to(&current_usage, &used);
-      }
-
-      /*
        * Print the information
        */
       print_time(data, &usage, 19);