UNIX for Advanced & Expert Users

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <pthread.h>

static pthread_t ptchild;
void* childthread(void* arg)
{
    struct sched_param pr;
    int ret = 9;
    int policy;

    pthread_getschedparam(pthread_self(), &policy, &pr);
    printf("Child Thread Up PL%d PRI%d!\n", policy, pr.sched_priority); //The result here 

    policy = SCHED_RR;
    pr.sched_priority = 19;
    pthread_setschedparam(pthread_self(), policy, &pr);
    sleep(1);

    pthread_getschedparam(pthread_self(), &policy, &pr);
    printf("Child Thread Up PL%d PRI%d!\n", policy, pr.sched_priority); //resutl set

    sleep(1);
    printf("child exit\n");
    pthread_exit((void*)ret);
}

void main(void)
{
    pthread_attr_t attr;
    struct sched_param pr;
    int ret;
    void* childret;

    pr.sched_priority = 19;
    
#if 1
    printf("%d\n", pthread_attr_init(&attr));
    printf("%d\n", pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE));
    printf("%d\n", pthread_attr_setschedpolicy(&attr, SCHED_RR));
    printf("%d\n", pthread_attr_setschedparam(&attr, &pr));

#endif

    if(ret = pthread_create(&ptchild, &attr, &childthread, NULL)<0){
        printf("Thread Create Err %d\n", ret);
    }

    /* Wait write Process end, then cancel report thread */
    if(ret = pthread_join(ptchild, &childret) < 0){
        printf("Thread Join Err %d\n", ret);

    }
    else{
        printf("joined, ret = %d\n", (int)childret);
    }
    return;    

}

0
0
0
0
Child Thread Up PL0 PRI0!   <- strange here, policy & prio not set
Child Thread Up PL2 PRI19!  <- in thread settings worked?
child exit
joined, ret = 9

man pthread_attr_setinheritsched