A locked state managed by the blocker greatly reduces {HEAD ~ corner cases} and simplifies solutions in {TAIL ~ the few remaining corner cases} 
A locked state managed by the blocker greatly reduces { HEAD ~ corner cases } and simplifies solutions in { TAIL ~ the few remaining corner cases }
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL