Core mutex seize method

[Andrei Dimitrief-Jianu]

rHello,

Below is an excerpt from cpukit/score/inline/rtems/score/coremutex.inl.

Can anyone argue that the first 'if' statement is not thread safe?

What is the condition that prevents the executing thread from being
preempted by another thread,
a thread that might compete for the same mutex, right before executing
 the_mutex->lock = CORE_MUTEX_LOCKED;?


Thanks,
Andrei.


[...]

RTEMS_INLINE_ROUTINE int _CORE_mutex_Seize_interrupt_trylock_body(
  CORE_mutex_Control  *the_mutex,
  ISR_Level           *level_p
)
{
  Thread_Control   *executing;

  /* disabled when you get here */

  executing = _Thread_Executing;
  executing->Wait.return_code = CORE_MUTEX_STATUS_SUCCESSFUL;
  if ( !_CORE_mutex_Is_locked( the_mutex ) ) {
    the_mutex->lock       = CORE_MUTEX_LOCKED;
    the_mutex->holder     = executing;
    the_mutex->holder_id  = executing->Object.id;
    the_mutex->nest_count = 1;
    if ( _CORE_mutex_Is_inherit_priority( &the_mutex->Attributes ) ||
         _CORE_mutex_Is_priority_ceiling( &the_mutex->Attributes ) ){

#ifdef __RTEMS_STRICT_ORDER_MUTEX__
       _Chain_Prepend_unprotected( &executing->lock_mutex,
                                   &the_mutex->queue.lock_queue );
       the_mutex->queue.priority_before = executing->current_priority;
#endif

      executing->resource_count++;
    }

[...]