nsd/serv.c has the additional comment before running NsRunAtReadyProcs (which results in SockReady calls):
/*
* If this thread just free'd up the busy server,
* run the ready procs to signal other subsystems.
*/
I don't see any correlation with crashes; these usually occur in my log after a hefty scheduled proc finally finishes running. No idea what, if anything, would cause nssock to want to wait for a scheduled proc to finish.