In this manner, fair arbitration is assured for {HEAD ~ other CPUs} contending for {TAIL ~ control} of the system bus 
contending for
In this manner , fair arbitration is assured for { HEAD ~ other CPUs } contending for { TAIL ~ control } of the system bus
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH