CMSIS_5: osRtxThreadListPut hangs when the thread is already on the list

My application hangs occasionally in this kernel function. Examination of the arguments in a debugger shows that when the second argument (the thread) is already on the list represented by the first argument. In this situation the function never returns, and the RTX kernel becomes hung.

/// Put a Thread into specified Object list sorted by Priority (Highest at Head).
/// \param[in]  object          generic object.
/// \param[in]  thread          thread object.
void osRtxThreadListPut (volatile os_object_t *object, os_thread_t *thread) {
  os_thread_t *prev, *next;
  int32_t      priority;

  if (thread == NULL) {
    return;
  }

  priority = thread->priority;

  prev = (os_thread_t *)(uint32_t)object;
  next = object->thread_list;
  while ((next != NULL) && (next->priority >= priority)) {
    prev = next;
    next = next->thread_next;
  }
  thread->thread_prev = prev;
  thread->thread_next = next;
  prev->thread_next = thread;
  if (next != NULL) {
    next->thread_prev = thread;
  }
}

In this case, the loop never exits because the next pointer is always non-NULL and the priority of the thread is always equal to the priority of the item in the list (since they’re actually the same object). I’ve seen this occur while managing the round-robin thread list and also while having a thread wait for EventFlags.

osRtxThreadListPut already tries to be somewhat defensive by returning early when the passed thread is NULL. It should gracefully handle the case where the thread is already on the list.

Perhaps these application hangs are due to some other misconfiguration on my part, but whatever the root cause, tracking down the fix is more difficult because the kernel itself hangs.