Question

我正在学习如何在C中使用Pthread。我尝试使用pthread_mutex_lock。当锁定成功时，它应该返回0。但是我的程序总是返回22 - 无效的参数。

代码如下：

pthread_mutex_lock用于work_function

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

#define N 2

void *work_function(void *param);

int count=0;
pthread_mutex_t mut;

int main(int args, char **argv)
{
    pthread_t tid[N];
    long int iterations = atoi(argv[1]);

    pthread_create(&tid[0], NULL, work_function, (void *) iterations);
    pthread_create(&tid[1], NULL, work_function, (void *) iterations);

    pthread_join(tid[1], NULL);
    pthread_join(tid[0], NULL);

    if (count != iterations * 2)
        printf("Error: %d\n",count);
    else
        printf("Value as expected: count = %d\n", count);

    pthread_exit(NULL);
}

void *work_function(void *param)
{
    long int max_iter = (long int) param;
    int i, tmp;

    pid_t pid = getpid();
    pthread_t id = pthread_self();

    i = pthread_mutex_lock(&mut);
    printf("%d\n", i);
    for(i = 0; i < max_iter; i++) {
        tmp = count;
        tmp ++;
        printf("in thread: pid=%d and id=%u count=%d new\n", (unsigned int) pid, (unsigned int) id, count);
        // sleep(1);
        count = tmp;
        printf("haha\n");
    }
    pthread_mutex_unlock(&mut);

    pthread_exit(NULL); 
}

当3作为命令行参数传入时，会产生以下结果。

22
22
in thread: pid=36767 and id=6819840 count=0 new
in thread: pid=36767 and id=7356416 count=0 new
haha
haha
in thread: pid=36767 and id=6819840 count=1 new
in thread: pid=36767 and id=7356416 count=1 new
haha
haha
in thread: pid=36767 and id=6819840 count=2 new
in thread: pid=36767 and id=7356416 count=2 new
haha
haha
Error: 3

Answer 1

通过在pthread_mutex_t mut方法下放置以下代码，初始化main解决了我的问题。

pthread_mutex_init(&mut, NULL);

pthread_mutex_lock在C

1 个答案: