使用CAS实现无锁列队-链表

Posted 2021-01-09 myd620

#include <stdlib.h>
#include <stdio.h>
#include <pthread.h>
#include <iostream>
#include <sys/time.h>
#include <pthread.h>

using namespace std;

#define MAXLEN 200000

#define NUM_THREADS 8

#define CAS __sync_bool_compare_and_swap
#define FAA __sync_fetch_and_add
#define FAS __sync_fetch_and_sub
#define VCAS __sync_val_compare_and_swap

struct node{
    int num;
    node * next;
    node(int i, node* n) :
        num(i), next(n)
    {}
};


struct list{
    node *head;
    node *tail;
    pthread_mutex_t  lock;
    int count;
};

void init(list *plist)
{
    node *tmp = new node(0, NULL);
    plist->head = tmp;
    plist->tail = tmp;
    plist->count = 0;
    pthread_mutex_init(&(plist->lock), NULL);
}



int enque_lock(list *plist, int num)
{
    node *tmp = new node(num, NULL);
    pthread_mutex_lock(&(plist->lock));

    plist->tail->next = tmp;
    plist->tail = tmp;
    plist->count++;
    pthread_mutex_unlock(&(plist->lock));
    return 0;
}
int enque(list *plist, int num)
{
    node *p = NULL;
    node *tmp = new node(num, NULL);
    do
    {
        p = plist->tail;
    } while (CAS(&(p->next), NULL, tmp) == false);
    CAS(&(plist->tail), p, tmp);

    FAA(&(plist->count), 1);
    return 0;
}


void  deque(list *plist)
{
    node *tmp = NULL;
    do{
        tmp = plist->head;
        if (plist->head == plist->tail)
        {
            printf("err
");
            return;
        }
    } while (CAS(&(plist->head), tmp, tmp->next) == false);
    FAS(&(plist->count), 1);
    delete tmp;
    return;
}

void *SendMsg(void* p)
{
    struct timeval tv_begin, tv_end;
    gettimeofday(&tv_begin, NULL);
    int i = 0;
    while (i++ < MAXLEN)
    {
        enque((list*)p, i);
    }
    gettimeofday(&tv_end, NULL);
    long timeinterval = (tv_end.tv_sec - tv_begin.tv_sec) * 1000000 + (tv_end.tv_usec - tv_begin.tv_usec);
    printf("cost %llu us
", timeinterval);
}


void *SendMsg2(void* p)
{
    struct timeval tv_begin, tv_end;
    gettimeofday(&tv_begin, NULL);
    int i = 0;
    while (i++ < MAXLEN)
    {
        enque_lock((list*)p, i);
    }
    gettimeofday(&tv_end, NULL);
    long timeinterval = (tv_end.tv_sec - tv_begin.tv_sec) * 1000000 + (tv_end.tv_usec - tv_begin.tv_usec);
    printf("cost %llu us
", timeinterval);
}



int main(void)
{
    int rc, i;
    pthread_t thread[NUM_THREADS];
    list  ll;
    init(&ll);
    for (i = 0; i < NUM_THREADS; i++)
    {
        printf("Creating thread %i
", i);
        rc = pthread_create(&thread[i], NULL, SendMsg, (void*)&ll);
        if (rc)
        {
            printf("ERROR; return code is %d
", rc);
            return -1;
        }
    }

    for (i = 0; i < NUM_THREADS; i++)
    {
        pthread_join(thread[i], NULL);
    }

    while (ll.count > 0)
    {
        deque(&ll);
    }


    for (i = 0; i < NUM_THREADS; i++)
    {
        printf("Creating thread %i
", i);
        rc = pthread_create(&thread[i], NULL, SendMsg2, (void*)&ll);
        if (rc)
        {
            printf("ERROR; return code is %d
", rc);
            return -1;
        }
    }

    for (i = 0; i < NUM_THREADS; i++)
    {
        pthread_join(thread[i], NULL);
    }
    return 0;
}

　　测试结果如下： 

Creating thread 0
Creating thread 1
Creating thread 2
Creating thread 3
Creating thread 4
Creating thread 5
Creating thread 6
Creating thread 7
cost 227839 us
cost 228055 us
cost 228034 us
cost 228179 us
cost 228274 us
cost 228328 us
cost 228413 us
cost 228433 us
Creating thread 0
Creating thread 1
Creating thread 2
Creating thread 3
Creating thread 4
Creating thread 5
Creating thread 6
Creating thread 7
cost 486283 us
cost 487499 us
cost 488358 us
cost 488677 us
cost 489118 us
cost 489658 us
cost 489657 us
cost 489735 us

加锁版 耗时 比无锁版耗时多一倍