Function indirect_lock

thread/thread.cpp:1507–1519

    }

    template<typename T, typename PT = T*> inline
    T* indirect_lock(volatile PT* ppt, T* end)
    {
    again:
        T* x = *ppt;
        if (!x || x == end)
            return nullptr;
        x->lock.lock();
        if (x == *ppt)
            return x;
        x->lock.unlock();
        goto again;
    }
    inline thread* indirect_lock(thread** ppt)
    {
        return indirect_lock<thread>(ppt, nullptr);