What to do with Thread_Control::resource_count?

[Sebastian Huber]

Hello,

due to the new thread priority management, the 
Thread_Control::resource_count is no longer needed to maintain the 
thread priority. The only relevant user of the thread resource count is

static void _Thread_Make_zombie( Thread_Control *the_thread )
{
   if ( _Thread_Owns_resources( the_thread ) ) {
     _Terminate(
       INTERNAL_ERROR_CORE,
       false,
       INTERNAL_ERROR_RESOURCE_IN_USE
     );
   }
[...]
}

which issues a fatal error in case a thread terminates with a non-zero 
resource count.

The question is now: should we maintain the resource count solely for 
this diagnostic purpose (the resource count increment/decrement is in 
the hot path of the mutex obtain/release)?

Terminating threads which own mutexes make these mutexes indestructible 
or lead to surprises in case the thread control block is re-used by a 
new thread. The current fatal error is new in 4.11, previous RTEMS 
didn't detect this situation.

If we decide to keep the resource count, then I suggest to use it for 
the no-protocol mutexes as well. This leads to code re-use with the 
priority inheritance mutexes.

-- 
Sebastian Huber, embedded brains GmbH

Address : Dornierstr. 4, D-82178 Puchheim, Germany
Phone   : +49 89 189 47 41-16
Fax     : +49 89 189 47 41-09
E-Mail  : sebastian.huber at embedded-brains.de
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