Each node of the queue holds {HEAD ~ a reference} to {TAIL ~ a task} that may be concurrently performed by multiple thread execution units, but each on a different subset of data 
Each node of the queue holds { HEAD ~ a reference } to { TAIL ~ a task } that may be concurrently performed by multiple thread execution units , but each on a different subset of data
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH