soft real-time scheduling

soft real-time scheduling

[Ankit Jain]

hi

 /* soft realtime scheduling variable */
   struct sched_param *p;


 /* set soft real-time scheduling */
   sched_getparam(0,p);
   p->sched_priority = 50;
   if (sched_setscheduler(0,SCHED_FIFO,p))
     fprintf(stderr,"Could not change scheduler
settings\n");

if anyone knows about this then i need some help

p is a pointer to the structure sched_param which is
defined in sched.h

this structure has a variable __sched_priority where i
have to set the priority of the process

p->sched_priority =50 this line gives a segmentation
fault. 
how t oaccess this variable (__sched_priority) of the
header file

thanks

ankit

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Re: soft real-time scheduling

[Muthukumar Ratty]

Hi, This is offtopic for this list.

from http://gcc.gnu.org/lists.html

"gcc-help is a relatively high volume list for people searching for help
in building or using GCC."


Anyway, for your question... i see few problems

1.    struct sched_param *p;
    sched_getparam(0,p);
Using unallocated memory. will result in SEGV

2. When you get 1 corrected, you may get another error
From man 2 sched_setscheduler
<snip>
EPERM  The calling process does not have appropriate  privileges.
<snip>

On Sun, 26 Sep 2004, Ankit Jain wrote:

> hi
>
>  /* soft realtime scheduling variable */
>    struct sched_param *p;
>
>
>  /* set soft real-time scheduling */
>    sched_getparam(0,p);
>    p->sched_priority = 50;
>    if (sched_setscheduler(0,SCHED_FIFO,p))
>      fprintf(stderr,"Could not change scheduler
> settings\n");
>
> if anyone knows about this then i need some help
>
> p is a pointer to the structure sched_param which is
> defined in sched.h
>
> this structure has a variable __sched_priority where i
> have to set the priority of the process
>
> p->sched_priority =50 this line gives a segmentation
> fault.
> how t oaccess this variable (__sched_priority) of the
> header file
>
> thanks
>
> ankit
>
> ________________________________________________________________________
> Yahoo! Messenger - Communicate instantly..."Ping"
> your friends today! Download Messenger Now
> http://uk.messenger.yahoo.com/download/index.html
>

Re: soft real-time scheduling

[Eljay Love-Jensen]

Hi Ankit,

You forgot to do...

p = malloc(sizeof(struct sched_param));

--Eljay

RE: soft real-time scheduling

[Bud Davis]

first off, this list is for gcc, not general programming.

p needs to have storage allocated. here is a safer way to do it:

#include <sched.h>
#include <stdio.h>
 
int main ()
{
   struct sched_param p;
 
 /* set soft real-time scheduling */
   sched_getparam(0,&p);
   p.sched_priority = 50;
   if (sched_setscheduler(0,SCHED_FIFO,&p))
     fprintf(stderr,"Could not change scheduler settings\n");
 
   return 0;
}


HTH,
bud davis