Brief

  • Locks: Atomicity
  • Condition Variables: Ordering
    • Fork/Join
    • Producer/Consumer

Semaphore

  • Lock + CV in one

Mutual Exclusion

  • Lock version
    lock();
crtical section
unlock();
  • Semaphore Version
    sem_wait(&lock)
critical section
sem_post(&lock);
    • Initialization: to use semaphore as lock
      • Initialize it to 1

Fork/Join 

  •  child() {
     ...
     sem_post(&s);
 }

 main() {
     sem_init(&s, 0);
     pthread_create(child);
     sem_wait(&s);
 }

Reader/Writer

  • Starvation