_LOCK
mutex_init(&_LOCK(f), NULL); \
mutex_lock(&_LOCK(fp));
cond_wait(&_LOCKCOND(fp), &_LOCK(fp));
mutex_unlock(&_LOCK(fp));
mutex_lock(&_LOCK(fp));
mutex_unlock(&_LOCK(fp));
mutex_lock(&_LOCK(fp));
mutex_unlock(&_LOCK(fp));