Method addToActiveList

src/threadlist.cpp:922–990

* * If there is a thread descriptor with the same tid, it must be from a dead * thread. Remove it now. * *****************************************************************************/

 *
 *****************************************************************************/
void
ThreadList::addToActiveList(Thread *th)
{
  int tid;
  Thread *thread;
  Thread *next_thread;

  lock_threads();

  // CONTEXT:  After fork(), we called:
  // ... -> initializeMtcpEngine() -> ThreadList::init() -> initThread()
  // -> addToActiveList()
  // NOTE:  After a call to fork(), only the calling thread continues to live.
  // Before initializeMtcpEngine() called init(), it called:
  // ... -> initializeMtcpEngine() -> ThreadSync::initMotherOfAll() ->
  // -> ThreadSync::initThread()
  // Logically, we would have set 'curThread = NULL;; inside
  // ThreadSync::initThread(), but it's inconvenient since curThread
  // is static (file-private).
  // So, initThread() created the new thread descriptor.  We make sure
  // to set curThread to th, the new descriptor, now, in case it wasn't
  // done yet.
  // We had also set curThread to NULL in ThreadList::init().  This also
  // makes logical sense, but only because a call to fork() allows
  // only the calling thread (caller of ThreadList::init()) to live on.
  // So, that solution seems less general.  So, we'll handle it here, too:
  curThread = th;

  tid = curThread->tid;
  JASSERT(tid != 0);

  // First remove duplicate descriptors.
  for (thread = activeThreads; thread != NULL; thread = next_thread) {
    next_thread = thread->next;
    if (thread != curThread && thread->tid == tid) {
      JTRACE("Removing duplicate thread descriptor") (thread->tid);

      // There will be at most one duplicate descriptor.
      threadIsDead(thread);
      continue;
    }

    // FIXME:  This causes segfault on second restart.  Why?
    // JASSERT(thread != curThread)(thread)
    // .Text("adding curThread, but it's already on activeThreads");

    /* NOTE:  ST_ZOMBIE is used only for the sake of efficiency.  We
     *   test threads in state ST_ZOMBIE using tgkill to remove them
     *   early (before reaching a checkpoint) so that the
     *   threadrdescriptor list does not grow too long.
     */
    if (thread->exiting) {
      /* if no thread with this tid, then we can remove zombie descriptor */
      if (-1 == THREAD_TGKILL(motherpid, thread->tid, 0)) {
        JTRACE("Killing zombie thread") (thread->tid);
        threadIsDead(thread);
      }
    }