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, 11 insertions, 15 deletions

diff --git a/cpukit/libcsupport/src/__times.c b/cpukit/libcsupport/src/__times.c
index ea6d1c65a7..a30f720f20 100644
--- a/cpukit/libcsupport/src/__times.c
+++ b/cpukit/libcsupport/src/__times.c
@@ -26,9 +26,11 @@
 #include <rtems.h>
 
 #include <sys/times.h>
-#include <time.h>
 #include <sys/time.h>
-#include <errno.h>
+
+#include <string.h>
+#include <time.h>
+
 #include <rtems/seterr.h>
 #include <rtems/score/todimpl.h>
 #include <rtems/score/timestamp.h>
@@ -42,11 +44,12 @@ clock_t _times(
 )
 {
   rtems_interval ticks, us_per_tick;
-  Thread_Control *executing;
 
   if ( !ptms )
     rtems_set_errno_and_return_minus_one( EFAULT );
 
+  memset( ptms, 0, sizeof( *ptms ) );
+
   /*
    *  This call does not depend on TOD being initialized and can't fail.
    */
@@ -62,11 +65,12 @@ clock_t _times(
    *  this thread.
    */
   {
+    Timestamp_Control  cpu_time_used;
     Timestamp_Control  per_tick;
     uint32_t           ticks_of_executing;
     uint32_t           fractional_ticks;
-    Per_CPU_Control   *cpu_self;
 
+    _Thread_Get_CPU_time_used( _Thread_Get_executing(), &cpu_time_used );
     _Timestamp_Set(
       &per_tick,
       rtems_configuration_get_microseconds_per_tick() /
@@ -74,25 +78,17 @@ clock_t _times(
       (rtems_configuration_get_nanoseconds_per_tick() %
 	  TOD_NANOSECONDS_PER_SECOND)
     );
-
-    cpu_self = _Thread_Dispatch_disable();
-    executing = _Thread_Executing;
-    _Thread_Update_cpu_time_used(
-      executing,
-      &_Thread_Time_of_last_context_switch
-    );
     _Timestamp_Divide(
-      &executing->cpu_time_used,
+      &cpu_time_used,
       &per_tick,
       &ticks_of_executing,
       &fractional_ticks
     );
-    _Thread_Dispatch_enable( cpu_self );
+
     ptms->tms_utime = ticks_of_executing * us_per_tick;
   }
+
   ptms->tms_stime  = ticks * us_per_tick;
-  ptms->tms_cutime = 0;
-  ptms->tms_cstime = 0;
 
   return ticks * us_per_tick;
 }