获取EPERM在Linux上呼吁SCHED_FIFO线程在pthread_create（）作为根时， [英] Getting EPERM when calling pthread_create() for SCHED_FIFO thread as root on Linux

问题描述

我试图用产卵或SCHED_FIFO SCHED_RR政策在Linux系统上的根，但我的电话线程在pthread_create（）正在返回1（EPERM）。对于在pthread_create（）的man page说EPERM指出，[T]他调用者没有适当的权限设置所需的调度参数或调度政策。应该不是根能够指定SCHED_FIFO或SCHED_RR？

I am trying to spawn threads with SCHED_FIFO or SCHED_RR policies as root on a Linux system but my calls to pthread_create() are returning 1 (EPERM). The man page for pthread_create() says that EPERM indicates that "[t]he caller does not have appropriate permission to set the required scheduling parameters or scheduling policy." Shouldn't root be able to specify SCHED_FIFO or SCHED_RR?

我已经剥离出来的code，创建一个线程进入一个小程序，确实仅此而已。它看起来我的权利，但仍然得到错误。我在做什么错了？

I've stripped out the code that creates a thread into a small program that does only that. It looks right to me but still gets the error. What am I doing wrong?

程序：

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

static void *_Thread(void *arg)
{
    (void)arg;
    printf("Thread running!\n");
    return NULL;
}

int main(void)
{
    int retVal;
    pthread_attr_t attr;
    struct sched_param schedParam;
    pthread_t thread;

    retVal = pthread_attr_init(&attr);
    if (retVal)
    {
        fprintf(stderr, "pthread_attr_init error %d\n", retVal);
        exit(1);
    }

    retVal = pthread_attr_setinheritsched(&attr, PTHREAD_EXPLICIT_SCHED);
    if (retVal)
    {
        fprintf(stderr, "pthread_attr_setinheritsched error %d\n", retVal);
        exit(1);
    }

    retVal = pthread_attr_setschedpolicy(&attr, SCHED_FIFO);
    if (retVal)
    {
        fprintf(stderr, "pthread_attr_setschedpolicy error %d\n", retVal);
        exit(1);
    }

    schedParam.sched_priority = 1;
    retVal = pthread_attr_setschedparam(&attr, &schedParam);
    if (retVal)
    {
        fprintf(stderr, "pthread_attr_setschedparam error %d\n", retVal);
        exit(1);
    }

    retVal = pthread_create(&thread,
                            &attr,
                            _Thread,
                            NULL);
    if (retVal)
    {
        fprintf(stderr, "pthread_create error %d\n", retVal);
        exit(1);
    }

    retVal = pthread_join(thread, NULL);
    if (retVal)
    {
        fprintf(stderr, "pthread_join error %d\n", retVal);
        exit(1);
    }

    printf("main run successfully\n");
    return 0;
}

该程序被编译并以root身份运行。运行时，其程序无法在调用在pthread_create，返回EPERM。

This program has been compiled and run as root. When run, it program fails at the call to pthread_create, returning EPERM.

更改线程调度SCHED_RR没有效果 - 通过EPERM仍然在pthread_create返回

Changing the thread to SCHED_RR scheduling has no effect - EPERM still returned by pthread_create.

更改线程调度SCHED_OTHER及其优先级为0，允许程序运行没有错误。

Changing the thread to SCHED_OTHER scheduling and its priority to 0 allows the program to run without error.

推荐答案

这必须是你的实时优先级软限制过于严格。

It must be that your real-time priority soft limit is too restrictive.

无论是电话的ulimit -r无限在shell中运行你的code之前。或致电了setrlimit（RLIMIT_RTPRIO，...）在code直接。

Either call ulimit -r unlimited in shell before running your code. Or call setrlimit(RLIMIT_RTPRIO, ...) directly in your code.

系统范围限制在 /etc/security/limits.conf文件设置。

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