Official usptream patch #2

Source: http://www.oracle.com/technology/products/berkeley-db/db/update/4.6.21/patch.4.6.21.html

*** mp/mp_region.c	2007-05-18 03:18:01.000000000 +1000
--- mp/mp_region.c	2008-06-24 13:15:56.000000000 +1000
***************
*** 249,256 ****
  		mtx_base = htab[0].mtx_hash;
  	}
  
  	if (mtx_base != MUTEX_INVALID)
! 		mtx_base += reginfo_off * htab_buckets;
  
  	/* Allocate hash table space and initialize it. */
  	if ((ret = __env_alloc(infop,
--- 249,262 ----
  		mtx_base = htab[0].mtx_hash;
  	}
  
+ 	/*
+ 	 * We preallocated all of the mutexes in a block, so for regions after
+ 	 * the first, we skip mutexes in use in earlier regions.  Each region
+ 	 * has the same number of buckets and there are two mutexes per hash
+ 	 * bucket (the bucket mutex and the I/O mutex).
+ 	 */
  	if (mtx_base != MUTEX_INVALID)
! 		mtx_base += reginfo_off * htab_buckets * 2;
  
  	/* Allocate hash table space and initialize it. */
  	if ((ret = __env_alloc(infop,