Function wt_thd_will_wait_for

mysys/waiting_threads.c:1011–1129

notify the system that a thread needs to wait for another thread called by a *waiter* to declare that it (thd) will wait for another thread (blocker) on a specific resource (resid). can be called many times, if many blockers own a blocking resource. but must always be called with the same resource id - a thread cannot wait for more than one resource at a time. @return WT_OK or WT_DEA

  performed for this new edge.
*/
int wt_thd_will_wait_for(WT_THD *thd, WT_THD *blocker,
                         const WT_RESOURCE_ID *resid)
{
  uint i;
  WT_RESOURCE *rc;
  DBUG_ENTER("wt_thd_will_wait_for");

  LF_REQUIRE_PINS(3);

  DBUG_PRINT("wt", ("enter: thd=%s, blocker=%s, resid=%lu",
                    thd->name, blocker->name, (ulong)resid->value));

  if (fix_thd_pins(thd))
    DBUG_RETURN(WT_DEADLOCK);

  if (thd->waiting_for == 0)
  {
    uint keylen;
    const void *key;
    /* XXX if (restype->make_key) key= restype->make_key(resid, &keylen); else */
    {
      key= resid;
      keylen= sizeof_WT_RESOURCE_ID;
    }

    DBUG_PRINT("wt", ("first blocker"));

retry:
    while ((rc= lf_hash_search(&reshash, thd->pins, key, keylen)) == 0)
    {
      WT_RESOURCE tmp;

      DBUG_PRINT("wt", ("failed to find rc in hash, inserting"));
      memset(&tmp, 0, sizeof(tmp));
      tmp.id= *resid;
      tmp.state= ACTIVE;

      if (lf_hash_insert(&reshash, thd->pins, &tmp) == -1) /* if OOM */
        DBUG_RETURN(WT_DEADLOCK);
      /*
        Two cases: either lf_hash_insert() failed - because another thread
        has just inserted a resource with the same id - and we need to retry.
        Or lf_hash_insert() succeeded, and then we need to repeat
        lf_hash_search() to find a real address of the newly inserted element.
        That is, we don't care what lf_hash_insert() has returned.
        And we need to repeat the loop anyway.
      */
    }
    if (rc == MY_ERRPTR)
      DBUG_RETURN(WT_DEADLOCK);

    DBUG_PRINT("wt", ("found in hash rc=%p", rc));

    rc_wrlock(rc);
    if (rc->state != ACTIVE)
    {
      DBUG_PRINT("wt", ("but it's not active, retrying"));
      /* Somebody has freed the element while we weren't looking */