pthread test

pthread.c

#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <unistd.h>
#include <errno.h>

void *perform_work(void *argument)
{
  int passed_in_value;
  passed_in_value = *((int *) argument);
  printf("Hello World! It's me, thread with argument %d!\n", passed_in_value);
  sleep(1);
}

int main(void)
{
  pthread_t thread;
  int thread_arg = 1;
  int result_code;
  struct sched_param param;
  int policy = 0;

  result_code = pthread_create(&thread, NULL, perform_work, (void *) &thread_arg);
  assert(0 == result_code);

  policy = SCHED_FIFO;

  result_code = pthread_setschedparam(thread, policy, &param);
  perror(NULL);
  fprintf(stderr, "result_code: %i, policy: %i\n", result_code, policy);
  fprintf(stderr, "EINVAL=%i, ENOTSUP=%i, ESRCH=%i\n", EINVAL, ENOTSUP, ESRCH);

  assert(0 == result_code);

  result_code = pthread_join(thread, NULL);
  assert(0 == result_code);

  exit(EXIT_SUCCESS);
}

As unprivileged user:

SCHED_FIFO

Operation not permitted
result_code: 1, policy: 1
EINVAL=22, ENOTSUP=86, ESRCH=3
assertion "0 == result_code" failed: file "thread.c", line 39, function "main"
Abort (core dumped) 

SCHED_RR

Operation not permitted
result_code: 1, policy: 2
EINVAL=22, ENOTSUP=86, ESRCH=3
assertion "0 == result_code" failed: file "thread.c", line 39, function "main"
Abort (core dumped) 

SCHED_OTHER

Invalid argument
result_code: 22, policy: 0
EINVAL=22, ENOTSUP=86, ESRCH=3
assertion "0 == result_code" failed: file "thread.c", line 39, function "main"
Abort (core dumped) 

As root:

SCHED_FIFO (success)

Undefined error: 0
result_code: 0, policy: 1
EINVAL=22, ENOTSUP=86, ESRCH=3
Hello World! It's me, thread with argument 1!

SCHED_RR (success)

Undefined error: 0
result_code: 0, policy: 2
EINVAL=22, ENOTSUP=86, ESRCH=3
Hello World! It's me, thread with argument 1!

SCHED_OTHER

Invalid argument
result_code: 22, policy: 0
EINVAL=22, ENOTSUP=86, ESRCH=3
assertion "0 == result_code" failed: file "thread.c", line 40, function "main"
Abort