mutex_unlock     2868 thread.c       static const char *mutex_unlock(mutex_t *mutex, rb_thread_t volatile *th);
mutex_unlock     2877 thread.c       	    const char *err = mutex_unlock(mutex, mutex->th);
mutex_unlock     3140 thread.c           err = mutex_unlock(mutex, GET_THREAD());
mutex_unlock     3157 thread.c       	err = mutex_unlock(mutex, GET_THREAD());