通过互斥锁来防止线程冲突

/*pthread_mutex.c*/
#include <pthread.h>
#include <stdlib.h>
#include <stdio.h>
#define MAX_LOOP 5000
int counter;
pthread_mutex_t p_m_t;
pthread_t p_tA,p_tB;
//通过互斥锁来防止多线程造成数据冲突
void *fnc(void * a)
{
    int i,val;
    for (i = 0; i < MAX_LOOP; i++)
    {
        /*线程1锁定，线程2等待解锁再执行，这个程序无论怎么执行都会加到10000
         *去掉互斥锁数据数据不会总加到10000,因为线程冲突引起的
         */
        pthread_mutex_lock(&p_m_t);
        val = counter;
        printf("this is %x: %d\n", (unsigned int)pthread_self(), (val + 1));
        counter = val + 1;
        pthread_mutex_unlock(&p_m_t);
    }
    return (void *)1;
}

int main()
{
    //创建两个线程
    pthread_create(&p_tA, NULL, &fnc, NULL);
    pthread_create(&p_tB, NULL, &fnc, NULL);
    pthread_join(p_tA, NULL);
    pthread_join(p_tB, NULL);
    return 1;
}