Explain how a reader–writer lock differs from an “ordinary” lock. What is a barrier? In what types of programs are barriers common? What does it mean for an algorithm to be nonblocking? What...

Explain how a reader–writer lock differs from an “ordinary” lock. What is a barrier? In what types of programs are barriers common? What does it mean for an algorithm to be nonblocking? What advantages do nonblocking algorithms have over algorithms based on locks?