下面我们将上面两个线程进行同步。

?

#include <pthread.h>
#include <stdio.h>
#include <unistd.h>


//初始化一个mutex(互斥体).
pthread_mutex_t counter_mutex = PTHREAD_MUTEX_INITIALIZER;

//define the first thread procedue.

void * thread_1_pro(void * arg)
{
	int * p_int_a=(int *) arg;
	while(1)
	{
		
		pthread_mutex_lock(&counter_mutex);	
		printf("------------- a = %d\n",*p_int_a);		
		(*p_int_a)++;
		 sleep(7);
		printf("+++++++++++++ a = %d\n",*p_int_a);
		pthread_mutex_unlock(&counter_mutex);
		//must add this sleep, give the chance to wake up thread_2_pro.
	    sleep(3);
		
    }	
}


void * thread_2_pro(void * arg)
{
	int * p_int_a=(int *) arg;
	while(1)
	{
		
		pthread_mutex_lock(&counter_mutex);
		printf("------------- b = %d\n",*p_int_a);	
		(*p_int_a)++;
		sleep(3);
		printf("+++++++++++++ b = %d\n",*p_int_a);
		pthread_mutex_unlock(&counter_mutex);
		//must add this sleep, give the chance to wake up thread_1_pro.
        sleep(3);
   }	
}


int main(int argc, char ** argv)
{
	pthread_t tidA, tidB;
    int common=0;
	pthread_create(&tidA, NULL, &thread_1_pro, &common);
	pthread_create(&tidB, NULL, &thread_2_pro, &common);
	sleep(120);
	//为什么需要最下面两行呢，如果没有，12秒后，主进程结束，会自动回收线程tidA, tidB,
	//这两行就是主进程中的线程要等这两个分支线程结束后，才执行join后面的内容。
	//pthread_join(tidA, NULL);
	//pthread_join(tidB, NULL);
	return 0;	
	return 0;	
}

?? ?输出结果：

?? ?可以看到，linux多线程和java多线程几乎一摸一样的。唯一的区别，好像就是在mutex后面必须加个sleep，有更多

?? ?的机会让别的线程获得机会去执行，如果不加这个，执行结果是完全不一样的。

------------- a = 0
+++++++++++++ a = 1
------------- b = 1
+++++++++++++ b = 2
------------- a = 2
+++++++++++++ a = 3
------------- b = 3
+++++++++++++ b = 4
------------- a = 4
+++++++++++++ a = 5
------------- b = 5
+++++++++++++ b = 6
------------- a = 6
+++++++++++++ a = 7
------------- b = 7
+++++++++++++ b = 8
------------- a = 8