无锁队列的实现

根据网上各种博客，然后自己写的一个无锁队列。

以后尝试性用这个代替线程池中的任务队列，应该这样会快很多。

#include <iostream>
#include <thread>
#include <atomic>

template<class T>
class LinkNode {
public:
    T data;
    LinkNode<T> *next;
};

template<class T>
class LockFreeQueue {
public:
    LockFreeQueue<T>() : head_(nullptr), tail_(nullptr), len(0) {
        LinkNode<T> *now = new LinkNode<T>;
        now->next = nullptr;
        head_ = tail_ = now;
    }
    void push(const T &data);
    T pop_front();
    bool empty();
private:
    LinkNode<T> *head_;
    LinkNode<T> *tail_;
    std::atomic_int len;
};

template <class T>
void LockFreeQueue<T>::push(const T &data) {
    LinkNode<T> * now = new LinkNode<T>;
    now->data=data;
    now->next= nullptr;
    LinkNode<T> * p1,*nxt;
    while(1){
        p1 = tail_;
        nxt = tail_->next;
        if (p1!=tail_) continue;
        if(nxt!= nullptr) {
            __sync_bool_compare_and_swap(&tail_,p1,nxt);
            continue;
        }
        if (__sync_bool_compare_and_swap(&tail_->next,nxt,now)==1) {
            break;
        }
    }
    __sync_bool_compare_and_swap(&tail_,p1,now);
    len++;
}

template <class T>
T LockFreeQueue<T>::pop_front() {
    LinkNode<T> *p1;
    do{
        p1=head_->next;
        if (p1== nullptr) {
            return -999999;
        }
    }while(__sync_bool_compare_and_swap(&head_->next,p1,p1->next)!=true);
    len--;
    return p1->data;
}

template <class T>
bool LockFreeQueue<T>::empty() {
    if (len==0) return true;
    else return false;
}

LockFreeQueue<int> queue;

void func1(void) {
    for (int i = 0; i < 10; i++) {
        queue.push(i);
    }
}

void func2(void) {
    for (int i = 30; i < 40; i++) {
        queue.push(i);
    }
}

void func3(void) {
    for (int i = 0; i < 10; i++) {
        std::cout << queue.pop_front() << " ";
    }
    std::cout << std::endl;
}

int main(int argc, char **argv) {
    std::thread t1(func1);
    std::thread t2(func2);
    std::thread t3(func3);
    std::thread t4(func3);
    t1.join();
    t2.join();
    t3.join();
    t4.join();
    return 0;
}