Class AtomicRunQ

thread/thread.cpp:624–720

    struct Switch { thread *from, *to; };

    class AtomicRunQ : public RunQ {
    public:
        vcpu_t* vcpu;
        mutable asymmetric_spinLock* plock;
        AtomicRunQ(const RunQ& runq = RunQ()) : RunQ(runq) {
            vcpu = current->get_vcpu();
            (plock = &vcpu->runq_lock) -> foreground_lock();
        }
        mutable bool update_current = false;
        void set_current(thread* th) const {
            current = th;
            update_current = true;
        }
        ~AtomicRunQ() {
            if (update_current)
                *pc = current;
            plock->foreground_unlock();
        }
        static void prefetch_context(thread* from, thread* to)
        {
#ifdef CONTEXT_PREFETCHING
            const int CACHE_LINE_SIZE = 64;
            auto f = *from->stack.pointer_ref();
            __builtin_prefetch(f, 1);
            // __builtin_prefetch((char*)f + CACHE_LINE_SIZE, 1);
            auto t = *to->stack.pointer_ref();
            __builtin_prefetch(t, 0);
            // __builtin_prefetch((char*)t + CACHE_LINE_SIZE, 0);
#endif
        }
        Switch remove_current(states new_state) const {
            assert(!current->single());
            auto from = current;
            auto to = from->remove_from_list();
            set_current(to);
            prefetch_context(from, to);
            from->state = new_state;
            to->state = states::RUNNING;
            return {from, to};
        }
        Switch _do_goto(thread* to) const {
            auto from = current;
            prefetch_context(from, to);
            from->state = states::READY;
            to->state = states::RUNNING;
            set_current(to);
            return {from, to};
        }
        Switch goto_next() const {
            assert(!current->single());
            return _do_goto(current->next());
        }
        Switch try_goto(thread* th) const {
            assert(th->vcpu == vcpu);
            th->remove_from_list();
            current->insert_after(th);
            return _do_goto(th);
        }