Mutex and Condvar

• rewritten to use explicit wait-queues in userspace

• pthread_cond_signal() and pthread_cond_broadcast() transfer the unblocked thread or threads directly to the wait-queue on the mutex and wake the first

• good news: compliant

• bad news

  • complicated

  • can't support process-shared

  • can't support priority-inheritence

• better than before, good enough for now