one of the documented procedures in this installation of the ACS
What it does:
Decrement the count of in-use threads. Used only for reporting matters. We've already allowed a new thread to begin. In actuality, we're incrementing the number completed, which will prevent us from blocking on a single shared value for the count. It also allows us better reporting capabilities.
Defined in: /web/philip/tcl/bulkmail-utils.tcl

Source code:

    ns_share bulkmail_threads_completed_mutex
    ns_share bulkmail_threads_completed

    ns_mutex lock $bulkmail_threads_completed_mutex
    catch {
	incr bulkmail_threads_completed
    ns_mutex unlock $bulkmail_threads_completed_mutex