pthreads_setaffinity_np：参数无效？

Question

我已经设法让我的

pthreads

程序运行起来。基本上我试图手动设置 4 个线程的亲和力，以便线程 1 在 CPU 1 上运行，线程 2 在 CPU 2 上运行，线程 3 在 CPU 3 上运行，线程 4 在 CPU 4 上运行。

编译后，我的代码适用于几个线程，但不适用于其他线程（似乎线程 1 永远无法工作），但运行相同的编译程序几次不同的结果会产生不同的结果。

例如：

$ ./a.out
Thread 3 is running on CPU 3  
pthread_setaffinity_np: Invalid argument  
Thread Thread 2 is running on CPU 2  

$ ./a.out
Thread 2 is running on CPU 2  
pthread_setaffinity_np: Invalid argument  
pthread_setaffinity_np: Invalid argument  
Thread 3 is running on CPU 3  
Thread 3 is running on CPU 3  

$ ./a.out
Thread 2 is running on CPU 2  
pthread_setaffinity_np: Invalid argument  
Thread 4 is running on CPU 4  
Thread 4 is running on CPU 4  

$ ./a.out
pthread_setaffinity_np: Invalid argument  

我的问题是“为什么会发生这种情况？另外，为什么消息有时会打印两次？”

这是代码：

#define _GNU_SOURCE
#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>
#include <sched.h>
#include <errno.h>

#define handle_error_en(en, msg) \
                                do { errno = en; perror(msg); exit(EXIT_FAILURE); } while (0)

void *thread_function(char *message)
{
    int s, j, number;
    pthread_t thread;
    cpu_set_t cpuset;

    number = (int)message;
    thread = pthread_self();    
    CPU_SET(number, &cpuset);

    s = pthread_setaffinity_np(thread, sizeof(cpu_set_t), &cpuset);
    if (s != 0)
    {
        handle_error_en(s, "pthread_setaffinity_np");
    }

    printf("Thread %d is running on CPU %d\n", number, sched_getcpu());

    exit(EXIT_SUCCESS);
}

int main()
{
    pthread_t thread1, thread2, thread3, thread4;
    int thread1Num = 1;
    int thread2Num = 2;
    int thread3Num = 3;
    int thread4Num = 4;
    int thread1Create, thread2Create, thread3Create, thread4Create, i, temp;

    thread1Create = pthread_create(&thread1, NULL, (void *)thread_function, (char *)thread1Num);
    thread2Create = pthread_create(&thread2, NULL, (void *)thread_function, (char *)thread2Num);
    thread3Create = pthread_create(&thread3, NULL, (void *)thread_function, (char *)thread3Num);
    thread4Create = pthread_create(&thread4, NULL, (void *)thread_function, (char *)thread4Num);

    pthread_join(thread1, NULL);
    pthread_join(thread2, NULL);
    pthread_join(thread3, NULL);
    pthread_join(thread4, NULL);

    return 0;
}

Answer 1

第一个 CPU 是 CPU 0 而不是 CPU 1。所以你需要改变你的 threadNums:

int thread1Num = 0;
int thread2Num = 1;
int thread3Num = 2;
int thread4Num = 3;

您应该这样使用 CPU_ZERO() 宏初始化

cpuset

：

CPU_ZERO(&cpuset);
CPU_SET(number, &cpuset);

也不要从线程中调用 exit()，因为它将停止整个进程及其所有线程：

退出（EXIT_SUCCESS）；  
返回0； // 使用它或者调用 pthread_exit()