Doubtful code in rtems_region_return_segment().

[Sergei Organov]

Hi,

The rtems_region_return_segment() routine looks like this (CVS trunc
version):

  _RTEMS_Lock_allocator();
  the_region = _Region_Get( id, &location );
  [...]
      status = _Region_Free_segment( the_region, segment );
      [...]  
      /*
       *  Switch from using the memory allocation mutex to using a
       *  dispatching disabled critical section.  We have to do this
       *  because this thread may unblock one or more threads that were
       *  waiting on memory.
       *
       *  NOTE: The following loop is O(n) where n is the number of
       *        threads whose memory request is satisfied.
       */
      _RTEMS_Unlock_allocator();
      _Thread_Disable_dispatch();
      [...]

1. The description of why we have to do this is unclear in the first
   place, -- why unblocking of threads should be done with the allocator
   unlocked? Is it strictly necessary, or is it just an optimization, or
   what?

2. If this is indeed necessary, shouldn't _Thread_Disable_dispatch be
   called before _RTEMS_Unlock_allocator to avoid races? Besides,
   similar code in the rtems_region_get_segment does it in reverse order
   indeed.

Thanks in advance for any clarification of the issue.

-- 
Sergei.