Core mutex seize method

[Gedare Bloom]

iirc it is the caller's responsibility to disable dispatching or
interrupts prior to calling CORE_mutex_Seize

On Fri, Oct 26, 2012 at 2:43 PM, Andrei Dimitrief-Jianu
<andrei.dimitrief.jianu at gmail.com> wrote:
> 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++;
>     }
>
> [...]
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