checkpthread

#!/bin/sh
cat > wje_q.c <<EOD
#include <errno.h>
#include <pthread.h>
#include <sched.h>
#include <stdio.h>
#include <stdlib.h>

void *second_thread_run_function(void *arg)
{
  printf("inside second thread\n");

  return NULL;

} /* second_thread_run_function() */

int main(void)
{
  int                status;

  pthread_t          second_thread_id;

  pthread_attr_t     thread_attr;

  struct sched_param thread_param;

  if(pthread_attr_init(&thread_attr))
  {
    fprintf(stderr,
            "error pthread_attr_init()\n"
           );

    exit(1);
  }

  if(pthread_attr_setschedpolicy(&thread_attr,
                                 SCHED_RR
                                )
    )
  {
    fprintf(stderr,
            "error pthread_attr_setschedpolicy()\n"
           );

    exit(1);
  }

  printf("%d %d\n",
         sched_get_priority_min(SCHED_RR),
         sched_get_priority_max(SCHED_RR)
        );

  thread_param.sched_priority=(sched_get_priority_min(SCHED_RR)
                              +sched_get_priority_max(SCHED_RR)
                              )
                              /2;

  if(pthread_attr_setschedparam(&thread_attr,
                                &thread_param
                               )
    )
  {
    fprintf(stderr,
            "error pthread_attr_setschedparam()\n"
           );

    exit(1);
  }

  if(pthread_attr_setinheritsched(&thread_attr,
                                  PTHREAD_EXPLICIT_SCHED
                                 )
    )
  {
    fprintf(stderr,
            "error pthread_attr_setinheritsched()\n"
           );

    exit(1);
  }

  status=pthread_create(&second_thread_id,
                        &thread_attr,
                        second_thread_run_function,
                        NULL
                       );

  if(status!=0)
  {
    if(status==EPERM)
    {
      fprintf(stderr,
              "pthread_create() got EPERM\n"
             );
    }
    else
    if(status==EINVAL)
    {
      fprintf(stderr,
              "pthread_create() got EINVAL\n"
             );
    }
    else
    {
      fprintf(stderr,
              "pthread_create() got neither EPERM nor EINVAL\n"
             );
    }

    fprintf(stderr,
            "pthread_create() got error %d\n",
            status
           );

    errno=status;

    perror("pthread_create()");

    exit(1);
  }

  if(pthread_join(second_thread_id,
                  NULL
                 )
    )
  {
    fprintf(stderr,
            "error pthread_join()\n"
           );

    exit(1);
  }

  return 0;

} /* main() */

EOD
gcc -pthread -Wall wje_q.c -o wje_q
./wje_q