More Locks

Question 1

We know that “Spin Locks” are not optimal because precious CPU time gets used by spinning. The solution to that is a system call provided by the OS called “yield”.

• What does it do?
• What is the problem with “yield”?

Answer 1

• Instead of “spin waiting” we use yield() to give the CPU time to another process.
  There are two problems:
  1. Scalability: With 100 threads maybe 99 need to yield.
  2. Fairness: Some threads can yield to death (starve)

Question 2

Explain the usage of a condition variable.

Answer 2

(Use the spick for help)