Can't set the schedual parameter of threads in linux

[yang]

Hello,
    I encounter a problem when I transplant application.
    There is no effect to the pthread when I call pthread_setschedparam() function in test program,  and it's policy and priority are stilll zero, not what I expected, after call pthread_getschedparam(). The codes  is as the follow:

#include <sched.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <linux/ipc.h>
#include <linux/msg.h>
#include <errno.h>
#include <stddef.h>
#include <string.h>

void * func()
{
        while (1);
    return;
}

int main()
{
    pthread_attr_t tattr;
    pthread_t tid;
    int policy;
    int ret;
    int newprio = 20;
    struct sched_param param;

    ret = pthread_attr_init (&tattr);
    if (ret != 0)
    {
        printf("Error in init: %s\n", strerror(errno));
    }

    ret = pthread_attr_getschedparam (&tattr, &param);
    if (ret != 0)
    {
        printf("Error in get after init: %s\n", strerror(errno));
    }
    ret = pthread_attr_setdetachstate(&tattr, PTHREAD_CREATE_DETACHED);
   if (ret != 0)
    {
        printf("Error in setdea: %s\n", strerror(errno));
    }
    ret = pthread_attr_setschedpolicy(&tattr, SCHED_RR);
    if (ret != 0)
    {
        printf("Error in setpolicy: %s\n", strerror(errno));
    }

    param.sched_priority = newprio;
    ret = pthread_attr_setschedparam (&tattr, &param);
    if (ret != 0)
    {
        printf("Error in set: %s\n", strerror(errno));
    }

    ret = pthread_create (&tid, &tattr, (int*) func, NULL);
    if (ret != 0)
    {
        printf("Error in create: %s\n", strerror(errno));
    }

    param.sched_priority = -1;
    ret = pthread_getschedparam (tid, &policy, &param);
    if (ret != 0)
    {
        printf("Error in get after create: %d %s\n", ret, strerror(errno));
    }

    printf("policy: %d\tpriority: %d\n", policy, param.sched_priority);

    return 0;

}

    The output is :
    policy: 0    priority: 0

    Would you like to tell me how to set the policy and priority to pthreads in Red Hat.? Thank you very much!
    Best regards,
                                     yang


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