以下案例是兩個執行緒同時訪問一個全域性worker變數，並分別對裡面的成員counter進行增長

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

#define MAX_NUM 5000

typedef struct 
{
	int counter;
	pthread_mutex_t counter_mutex;
}COUNTER;

COUNTER worker;

void *run(void *arg)
{
	int i = 0;
	int val = 0;
	char line[1024] = {0};
	for (; i < MAX_NUM; ++i)
	{
		pthread_mutex_lock(&worker.counter_mutex);
		val = worker.counter;
		sprintf(line, "thread = %d, counter = %d\n", (int)pthread_self(), val+1);
		write(STDOUT_FILENO, line, strlen(line));
		worker.counter = val + 1;
		memset(line, 0, strlen(line));
		pthread_mutex_unlock(&worker.counter_mutex);
	}
}

int main(int argc, char *argv[])
{
	pthread_t tid1, tid2;
	
	worker.counter = 0;
	pthread_mutex_init(&worker.counter_mutex, NULL);
	
	pthread_create(&tid1, NULL, run, NULL);
	pthread_create(&tid2, NULL, run, NULL);
	
	pthread_join(tid1, NULL);
	pthread_join(tid2, NULL);
	
	pthread_mutex_destroy(&worker.counter_mutex);
	return 0;
}