cas

http://blog.163.com/xychenbaihu@yeah/blog/static/1322296552013373236132/

https://www.cnblogs.com/wzjhoutai/p/6838104.html

 

 

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<pthread.h>

int count = 0;
void *func_cas(void*arg)
{
    int i=0;
    int temp = 0;

    for(i = 0;i < 20000;i++)
    {
        while(1)
        {
            temp = count;
            if(__sync_bool_compare_and_swap(&count, temp, temp+1))
                break;
        }

    }
}

void *func(void*arg)
{
    int i=0;

    for(i = 0;i < 20000;i++)
    {
        count++;
    }
}


int main()
{
    pthread_t id[10];
    int i=0;
    for(i=0 ;i< sizeof(id)/sizeof(id[0]);i++)
    {
        pthread_create(&id[i],NULL,func_cas,NULL);
    }

    for(i=0 ;i< sizeof(id)/sizeof(id[0]);i++)
    {
        pthread_join(id[i],NULL);
    }

    printf("count = %d
",count);

    count = 0;

    for(i=0 ;i< sizeof(id)/sizeof(id[0]);i++)
    {
        pthread_create(&id[i],NULL,func,NULL);
    }

    for(i=0 ;i< sizeof(id)/sizeof(id[0]);i++)
    {
        pthread_join(id[i],NULL);
    }    
    printf("
count = %d
",count);
}