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\n",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("\ncount = %d\n",count);
}