码海拾遗：Linux多线程mutex锁

　　多线程计数，每个线程累加10个数。

　　实现：

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

pthread_mutex_t num_lock;

int num = 0;
int sum = 0;

void* foo1()
{
#if 1
    pthread_mutex_lock(&num_lock);
    for(int i = 0;i<10;++i)
    {
        num += 1;
        sum += num;
        printf("thread 1,num = %d,sum = %d
",num,sum);
        usleep(10);
    }
    pthread_mutex_unlock(&num_lock);
#else
    for(int i = 0;i<10;++i)
    {
        num += 1;
        sum += num;
        printf("thread 1,num = %d,sum = %d
",num,sum);
        usleep(10);
    }
#endif
    return NULL;
}

void* foo2()
{
#if 1
    pthread_mutex_lock(&num_lock);
    for(int i = 0;i<10;++i)
    {
        num += 1;
        sum += num;
        printf("thread 2,num = %d,sum = %d
",num,sum);
        usleep(10);
    }
    pthread_mutex_unlock(&num_lock);
#else
    for(int i = 0;i<10;++i)
    {
        num += 1;
        sum += num;
        printf("thread 2,num = %d,sum = %d
",num,sum);
        usleep(10);
    }
#endif
    return NULL;
}

int main(int argc,char* argv[])
{
    pthread_t tid1,tid2;
    int err;

    pthread_mutex_init(&num_lock,NULL);

    err = pthread_create(&tid1,NULL,foo1,NULL);
    if(err != 0)
    {
        printf("error code:%d,reason:%s
",err,strerror(err));
        return -1;
    }

    err = pthread_create(&tid2,NULL,foo2,NULL);
    if(err != 0)
    {
        printf("error code:%d,reason:%s
",err,strerror(err));
        return -1;
    }

    //for(int i = 0;i<10;++i)
    //    printf("main thread, num = %d
",num++);

    err = pthread_join(tid1,NULL);
    if(err != 0)
    {
        printf("error code:%d,reason:%s
",err,strerror(err));
        return -1;
    }
    err = pthread_join(tid2,NULL);
    if(err != 0)
    {
        printf("error code:%d,reason:%s
",err,strerror(err));
        return -1;
    }

    pthread_mutex_destroy(&num_lock);

    return 0;
}