Scheduler Problem ????

Scheduler Problem ????

[Emmanuel Fleury]

Hi all,

I am running a 2.6.4 (with preemptible kernel activated). 
What I did is the following:

1) Compile the sched_test.c program (at the end of the mail):

[root@hermes sched]$ gcc -o sched_test sched_test.c

2) Set the priority of the root shell as the highest:
[root@hermes sched]$ ps
  PID TTY          TIME CMD
 1519 pts/0    00:00:00 bash
 2020 pts/0    00:00:00 ps
[root@hermes sched]$ chrt -f -p 99 1519

3) Run sched_test:
[root@hermes sched]$ chrt -f 10 ./sched_test 100
bye now.
  


Here during the execution of sched_test everything is frozen.


Did I do something wrong ????

sched_test.c
=============
#include <sys/time.h>
#include <time.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>

int main(int argc, char *argv[])
{
  int end_time;
  struct timeval now;

  if (argc < 2) 
    {
      end_time = 1;
    }
  else
    {
      end_time = atoi(argv[1]);
    }

  gettimeofday(&now, NULL);

  end_time += now.tv_sec + 1;

  do{
    gettimeofday(&now, NULL);
    
  }while (now.tv_sec < end_time);

  printf("bye now.\n");
  return 0;
}
==========

Regards
-- 
Emmanuel Fleury

Computer Science Department, |  Office: B1-201
Aalborg University,          |  Phone:  +45 96 35 72 23
Fredriks Bajersvej 7E,       |  Fax:    +45 98 15 98 89
9220 Aalborg East, Denmark   |  Email:  fleury@cs.auc.dk

Re: Scheduler Problem ????

[Nick Piggin]

Emmanuel Fleury wrote:

>Hi all,
>
>I am running a 2.6.4 (with preemptible kernel activated). 
>What I did is the following:
>
>1) Compile the sched_test.c program (at the end of the mail):
>
>[root@hermes sched]$ gcc -o sched_test sched_test.c
>
>2) Set the priority of the root shell as the highest:
>[root@hermes sched]$ ps
>  PID TTY          TIME CMD
> 1519 pts/0    00:00:00 bash
> 2020 pts/0    00:00:00 ps
>[root@hermes sched]$ chrt -f -p 99 1519
>
>3) Run sched_test:
>[root@hermes sched]$ chrt -f 10 ./sched_test 100
>bye now.
>  
>
>
>Here during the execution of sched_test everything is frozen.
>
>
>Did I do something wrong ????
>
>

Realtime processes aren't preemptible at all by non realtime
processes or realtime processes of a lesser priority.