release(&cond->c_spinlock);
__pthread_unlock(&cond->c_lock);
int pthread_cond_signal(pthread_cond_t *cond){  pthread_descr th;  acquire(&cond->c_spinlock);  th = dequeue(&cond->c_waiting);  release(&cond->c_spinlock);  if (th != NULL) restart(th);  return 0;}