[lwip-users] Question about sys_arch.c *_free() vs. *_~set_invalid()

[Grant Edwards]

[Sorry for all of the porting questions, but the sys_arch.c file I'm
working with just doesn't seem to make sense.]

I don't understand how *_free() and *_set_invalid() are supposed to
interact.

In the code I've inherited, when *_free() is called, my sys_arch.c
code places the referenced kernel object (semaphore or mailbox) back
into the free pool and it becomes available to be reallocated and
placed into use.

The lwIP documentation states:

   void sys_sem_set_invalid(sys_sem_t *sem)

   Invalidate a semaphore so that sys_sem_valid() returns 0.
   ATTENTION: This does NOT mean that the semaphore shall be
   deallocated: sys_sem_free() is always called before calling this
   function!

Apparently the sequence is

  new(sem)
  free(sem)
  invalid(sem)

If invalid() is called for a particular semaphore _after_ that
semaphore has been free()ed, that semaphore may have already been
reallocated and might be in use by a different thread, socket,
whatever. Is the semaphore not supposed to be availble for
reallocation after being free()ed?

Are signal/wait calls on a mutex allowed between the free() call and
the set_invalid() call?

--
Grant