[Bug 2180] New: _TOD_Get_with_nanoseconds() is broken on SMP

[bugzilla-daemon at rtems.org]

https://www.rtems.org/bugzilla/show_bug.cgi?id=2180

             Bug #: 2180
           Summary: _TOD_Get_with_nanoseconds() is broken on SMP
    Classification: Unclassified
           Product: RTEMS
           Version: 4.11
          Platform: All
        OS/Version: RTEMS
            Status: NEW
          Severity: normal
          Priority: P3
         Component: cpukit
        AssignedTo: joel.sherrill at oarcorp.com
        ReportedBy: sebastian.huber at embedded-brains.de


We have

Timestamp_Control *_TOD_Get_with_nanoseconds(
  Timestamp_Control *snapshot,
  const Timestamp_Control *clock
)
{
  TOD_Control      *tod = &_TOD;
  ISR_lock_Context  lock_context;
  Timestamp_Control offset;
  Timestamp_Control now;
  uint32_t          nanoseconds;

  _TOD_Acquire( tod, &lock_context );
    nanoseconds = ( *tod->nanoseconds_since_last_tick )();
    now = *clock;
  _TOD_Release( tod, &lock_context );

  _Timestamp_Set( &offset, 0, nanoseconds );
  _Timestamp_Add_to( &now, &offset );

  *snapshot = now;

  return snapshot;
}

and

void _TOD_Tickle_ticks( void )
{
  TOD_Control       *tod = &_TOD;
  ISR_lock_Context   lock_context;
  Timestamp_Control  tick;
  uint32_t           nanoseconds_per_tick;

  nanoseconds_per_tick = rtems_configuration_get_nanoseconds_per_tick();

  /* Convert the tick quantum to a timestamp */
  _Timestamp_Set( &tick, 0, nanoseconds_per_tick );

  /* Update the counter of ticks since boot */
  _Watchdog_Ticks_since_boot += 1;

  _TOD_Acquire( tod, &lock_context );

  /* Update the uptime */
  _Timestamp_Add_to( &tod->uptime, &tick );

  /* Update the current TOD */
  _Timestamp_Add_to( &tod->now, &tick );

  _TOD_Release( tod, &lock_context );

  _TOD.seconds_trigger += nanoseconds_per_tick;
  if ( _TOD.seconds_trigger >= 1000000000UL ) {
    _TOD.seconds_trigger -= 1000000000UL;
    _Watchdog_Tickle_seconds();
  }
}

and (standard Clock driver)

#if defined(BSP_FEATURE_IRQ_EXTENSION) || \
    (CPU_SIMPLE_VECTORED_INTERRUPTS != TRUE)
void Clock_isr(void *arg)
{
#else
rtems_isr Clock_isr(rtems_vector_number vector);
rtems_isr Clock_isr(
  rtems_vector_number vector
)
{
#endif
  /*
   *  Accurate count of ISRs
   */
  Clock_driver_ticks += 1;

  #if CLOCK_DRIVER_USE_FAST_IDLE
    do {
      rtems_clock_tick();
    } while (
      _Thread_Heir == _Thread_Executing
        && _Thread_Executing->Start.entry_point
          == rtems_configuration_get_idle_task()
    );

    Clock_driver_support_at_tick();
    return;
  #else
    /*
     *  Do the hardware specific per-tick action.
     *
     *  The counter/timer may or may not be set to automatically reload.
     */
    Clock_driver_support_at_tick();

    #if CLOCK_DRIVER_ISRS_PER_TICK
      /*
       *  The driver is multiple ISRs per clock tick.
       */
      if ( !Clock_driver_isrs ) {
        rtems_clock_tick();

        Clock_driver_isrs = CLOCK_DRIVER_ISRS_PER_TICK;
      }
      Clock_driver_isrs--;
    #else
      /*
       *  The driver is one ISR per clock tick.
       */
      rtems_clock_tick();
    #endif
  #endif
}


Suppose we are between Clock_driver_support_at_tick() and _TOD_Tickle_ticks(). 
Now call _TOD_Get_with_nanoseconds() on another processor.  With most
nanoseconds extensions we observe now a serviced hardware clock interrupt and
the old _TOD.uptime value.

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