Function thread_yield_to

thread/thread.cpp:1316–1341

    }

    int thread_yield_to(thread* th) {
        if (unlikely(th == nullptr)) { // yield to any thread
            return thread_yield();
        }
        RunQ rq;
        if (unlikely(th == rq.current)) { // yield to current should just update time
            if_update_now();
            return 0;
        } else if (unlikely(th->vcpu != rq.current->vcpu)) {
            LOG_ERROR_RETURN(EINVAL, -1, "target thread ` must be run by the same vcpu as CURRENT!", th);
        } else if (unlikely(th->state == states::STANDBY)) {
            while (th->state == states::STANDBY)
                resume_threads(th->get_vcpu(), rq);
            assert(th->state == states::READY);
        } else if (unlikely(th->state != states::READY)) {
            LOG_ERROR_RETURN(EINVAL, -1, "target thread ` must be READY!", th);
        } else if (unlikely(rq.current->next() == th)) {
            return thread_yield();
        }

        auto sw = AtomicRunQ(rq).try_goto(th);
        if_update_now();
        rq.current->error_number = 0;
        switch_context(sw.from, sw.to);
        return rq.current->error_number;
    }

    __attribute__((always_inline)) inline
    Switch prepare_usleep(Timeout timeout, thread_list* waitq, RunQ rq = {})