使用CAS实现无锁列队-链表

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#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\n");             return;         }     } while (CAS(&(plist->head), tmp, tmp->next) == false);     FAS(&(plist->count), 1);<br>    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\n", 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\n", 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\n", i);         rc = pthread_create(&thread[i], NULL, SendMsg, (void*)&ll);         if (rc)         {             printf("ERROR; return code is %d\n", 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\n", i);         rc = pthread_create(&thread[i], NULL, SendMsg2, (void*)&ll);         if (rc)         {             printf("ERROR; return code is %d\n", 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