check, per request by Jeff Davis.
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/backend/port/unix_latch.c,v 1.2 2010/09/11 16:26:04 heikki Exp $
+ *   $PostgreSQL: pgsql/src/backend/port/unix_latch.c,v 1.3 2010/09/13 18:01:20 heikki Exp $
  *
  *-------------------------------------------------------------------------
  */
    if (selfpipe_readfd == -1)
        initSelfPipe();
 
+   /* sanity check */
    if (latch->owner_pid != 0)
        elog(ERROR, "latch already owned");
    latch->owner_pid = MyProcPid;