pthread_mutex_lock 在 C 中返回 22 [英] pthread_mutex_lock returns 22 in C

问题描述

我正在学习如何在 C 中使用 Pthread.我尝试使用 pthread_mutex_lock.锁定成功时应该返回0.但我的程序总是返回 22 - 无效参数.

I'm learning how to use Pthread in C. I've tried to use pthread_mutex_lock. It is supposed to return 0 when the locking is successful. But my program always returns 22 - invalid argument.

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产生以下结果.

The following result is produced when 3 is passed in as the command line argument.

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

推荐答案

Initializing pthread_mutex_t mut 解决了我的问题，将以下代码放在 main 方法下.

Initializing pthread_mutex_t mut solved my problem, by placing the following code under main method.

pthread_mutex_init(&mut, NULL);

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