Thread Synchronization

• Semaphores

  • Named vs. Unnamed
  • Part of POSIX.1b, but not Pthreads
  • More expensive
  • int sem_wait(sem_t *sem); (Dijkstra’s P),
  • int sem_post(sem_t *sem); (V)

• Read-Write Locks (X/Open extension)

  • Allows multiple simultaneous reads, serial writes
  • int pthread_rwlock_rdlock(pthread_rwlock_t *rw);
  • int pthread_rwlock_wrlock(pthread_rwlock_t *rw);
  • int pthread_rwlock_unlock(pthread_rwlock_t *rw);
  • Reader Preference, Writer Preference, Equal Preference

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