Unable set the priority for a pthread through pthread_setschedparam

Unable set the priority for a pthread through pthread_setschedparam

[Srinivas G.]

Dear All,

I have written a small thread program in C using the pthreads. I am able
to set the threads priority with pthread_setschedparam API when I login
as ROOT. If I login as a normal user other than ROOT, then the API
returns the error number 1 (EPERM). 

Please let me know whether a normal user can set the pthreads priority
with pthread_setschedparam API or not.

Here is the sample code for testing.

/* 
 * Creates two threads, one printing 10 "a"s, 
 * the other printing 10 "b"s.
 * Illustrates: thread creation, thread joining. 
 */

#include <stddef.h>
#include <stdio.h>
#include <unistd.h>
#include "pthread.h"
#include <errno.h>

void * process(void * arg)
{
  int i;
  fprintf(stderr, "Starting process %s\n", (char *) arg);
  for (i = 0; i < 10; i++) {
    write(1, (char *) arg, 1);
  }
  fprintf(stderr,"\n");

  return NULL;
}

int main()
{
  int retcode;
  pthread_t th_a, th_b;
  void * retval;
  struct sched_param sp;
  int esnRetVal = 0;
  pthread_attr_t attr;

  pthread_attr_init(&attr);
  pthread_attr_setinheritsched(&attr, PTHREAD_INHERIT_SCHED);
 
  retcode = pthread_create(&th_a, &attr, process, "a");
  if (retcode != 0) fprintf(stderr, "create a failed %d\n", retcode);

  sp.sched_priority = 30;
  esnRetVal = pthread_setschedparam(th_a, SCHED_RR, &sp);
  if(esnRetVal != 0)
  {
     printf("Failed to set the pthread sched param! esnRetVal = %d errno
= %d\n", esnRetVal, errno);
     return -1;
  } 

  retcode = pthread_create(&th_b, NULL, process, "b");
  if (retcode != 0) fprintf(stderr, "create b failed %d\n", retcode);

  retcode = pthread_join(th_a, &retval);
  if (retcode != 0) fprintf(stderr, "join a failed %d\n", retcode);

  retcode = pthread_join(th_b, &retval);
  if (retcode != 0) fprintf(stderr, "join b failed %d\n", retcode);

  return 0;
}

Thanks in advance.

With Regards,
Srinivas G

Re: Unable set the priority for a pthread through pthread_setschedparam

[Manish Katiyar]

On Tue, Feb 3, 2009 at 10:18 AM, Srinivas G.
<srinivasg@esntechnologies.co.in> wrote:
> Dear All,
>
> I have written a small thread program in C using the pthreads. I am able
> to set the threads priority with pthread_setschedparam API when I login
> as ROOT. If I login as a normal user other than ROOT, then the API
> returns the error number 1 (EPERM).
>
> Please let me know whether a normal user can set the pthreads priority
> with pthread_setschedparam API or not.

The man page says it all

              !EPERM!
                     the calling process does not have superuser permissions

you cannot unless you have superuser permissions.

Thanks -
Manish


>
> Here is the sample code for testing.
>
> /*
>  * Creates two threads, one printing 10 "a"s,
>  * the other printing 10 "b"s.
>  * Illustrates: thread creation, thread joining.
>  */
>
> #include <stddef.h>
> #include <stdio.h>
> #include <unistd.h>
> #include "pthread.h"
> #include <errno.h>
>
> void * process(void * arg)
> {
>  int i;
>  fprintf(stderr, "Starting process %s\n", (char *) arg);
>  for (i = 0; i < 10; i++) {
>    write(1, (char *) arg, 1);
>  }
>  fprintf(stderr,"\n");
>
>  return NULL;
> }
>
> int main()
> {
>  int retcode;
>  pthread_t th_a, th_b;
>  void * retval;
>  struct sched_param sp;
>  int esnRetVal = 0;
>  pthread_attr_t attr;
>
>  pthread_attr_init(&attr);
>  pthread_attr_setinheritsched(&attr, PTHREAD_INHERIT_SCHED);
>
>  retcode = pthread_create(&th_a, &attr, process, "a");
>  if (retcode != 0) fprintf(stderr, "create a failed %d\n", retcode);
>
>  sp.sched_priority = 30;
>  esnRetVal = pthread_setschedparam(th_a, SCHED_RR, &sp);
>  if(esnRetVal != 0)
>  {
>     printf("Failed to set the pthread sched param! esnRetVal = %d errno
> = %d\n", esnRetVal, errno);
>     return -1;
>  }
>
>  retcode = pthread_create(&th_b, NULL, process, "b");
>  if (retcode != 0) fprintf(stderr, "create b failed %d\n", retcode);
>
>  retcode = pthread_join(th_a, &retval);
>  if (retcode != 0) fprintf(stderr, "join a failed %d\n", retcode);
>
>  retcode = pthread_join(th_b, &retval);
>  if (retcode != 0) fprintf(stderr, "join b failed %d\n", retcode);
>
>  return 0;
> }
>
> Thanks in advance.
>
> With Regards,
> Srinivas G
> --
> To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>

RE: Unable set the priority for a pthread through pthread_setschedparam

[Srinivas G.]

> The man page says it all
> 
>               !EPERM!
>                      the calling process does not have superuser
> permissions
> 
> you cannot unless you have superuser permissions.
>

Dear Manish,

Thanks for the information.

I have seen the man pages and find the following.

EPERM  The caller does not have appropriate privileges to set the
specified
       scheduling policy and parameters.

I have tried to set the super user permissions to a normal user through
user and groups. However I found there are lot of different groups
exists like
adm
apache
avahi
bin
daemon
dbus
dip
etc.

Which groups shall I need to select for setting the super user
permissions?

Thanks in advance.

Thanks and Regards,
Srinivas G

Re: Unable set the priority for a pthread through pthread_setschedparam

[Manish Katiyar]

On Tue, Feb 3, 2009 at 11:57 AM, Srinivas G.
<srinivasg@esntechnologies.co.in> wrote:
>> The man page says it all
>>
>>               !EPERM!
>>                      the calling process does not have superuser
>> permissions
>>
>> you cannot unless you have superuser permissions.
>>
>
> Dear Manish,
>
> Thanks for the information.
>
> I have seen the man pages and find the following.
>
> EPERM  The caller does not have appropriate privileges to set the
> specified
>       scheduling policy and parameters.
>
> I have tried to set the super user permissions to a normal user through
> user and groups. However I found there are lot of different groups

one with id 0 .. see /etc/group

Thanks -
Manish

> exists like
> adm
> apache
> avahi
> bin
> daemon
> dbus
> dip
> etc.
>
> Which groups shall I need to select for setting the super user
> permissions?
>
> Thanks in advance.
>
> Thanks and Regards,
> Srinivas G
>
>

Re: Unable set the priority for a pthread through pthread_setschedparam

[Glynn Clements]

Srinivas G. wrote:

> I have written a small thread program in C using the pthreads. I am able
> to set the threads priority with pthread_setschedparam API when I login
> as ROOT. If I login as a normal user other than ROOT, then the API
> returns the error number 1 (EPERM). 
> 
> Please let me know whether a normal user can set the pthreads priority
> with pthread_setschedparam API or not.

Yes, subject to certain restrictions, which are detailed in the
sched_setscheduler(2) manpage.

In particular, a non-privileged process cannot set the real-time
priority higher than its RLIMIT_RTPRIO setting. You can change this
with an "rtprio" entry in /etc/security/limits.conf (settings are
applied on login, so changes won't affect existing login sessions).

Privilege is determined by the CAP_SYS_NICE capability.

-- 
Glynn Clements <glynn@gclements.plus.com>

RE: Unable set the priority for a pthread through pthread_setschedparam

[Srinivas G.]

Glynn Clements wrote:

> Yes, subject to certain restrictions, which are detailed in the
> sched_setscheduler(2) manpage.
> 
> In particular, a non-privileged process cannot set the real-time
> priority higher than its RLIMIT_RTPRIO setting. You can change this
> with an "rtprio" entry in /etc/security/limits.conf (settings are
> applied on login, so changes won't affect existing login sessions).
> 
> Privilege is determined by the CAP_SYS_NICE capability.

Thanks Glynn.

I have tried to set the RLIMIT_RTPRIO to 100 through
/etc/security/limits.conf. It was not defined previously, so I have
defined in the following way.

domain       type    item     value
#@srinivasg  soft    rtprio   100

After adding the above statement, I have restarted the system.

Then, I run my simple thread program. There is no luck. I got the same
error. I have posted the simple thread program in my first email.

What am I missing here? Please advice.

Thanks and Regards,
Srinivas G


 

Re: Unable set the priority for a pthread through pthread_setschedparam

[ben]

Srinivas G. a écrit :
> I have tried to set the RLIMIT_RTPRIO to 100 through
> /etc/security/limits.conf. It was not defined previously, so I have
> defined in the following way.
> 
> domain       type    item     value
> #@srinivasg  soft    rtprio   100
you must uncomment the line (remove the #)
then, the given group will have a soft rtprio limit to 100.
This will work, assuming your PAM configuration uses pam_limits.

> After adding the above statement, I have restarted the system.
> 
> Then, I run my simple thread program. There is no luck. I got the same
> error. I have posted the simple thread program in my first email.
> 
> What am I missing here? Please advice.
> 
> Thanks and Regards,
> Srinivas G
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RE: Unable set the priority for a pthread through pthread_setschedparam

[Glynn Clements]

Srinivas G. wrote:

> > Yes, subject to certain restrictions, which are detailed in the
> > sched_setscheduler(2) manpage.
> > 
> > In particular, a non-privileged process cannot set the real-time
> > priority higher than its RLIMIT_RTPRIO setting. You can change this
> > with an "rtprio" entry in /etc/security/limits.conf (settings are
> > applied on login, so changes won't affect existing login sessions).
> > 
> > Privilege is determined by the CAP_SYS_NICE capability.
> 
> Thanks Glynn.
> 
> I have tried to set the RLIMIT_RTPRIO to 100 through
> /etc/security/limits.conf. It was not defined previously, so I have
> defined in the following way.
> 
> domain       type    item     value
> #@srinivasg  soft    rtprio   100

First, as Ben says, you must uncomment the line. Second, you may also
need to set the hard limit. You can use "ulimit -a" (or -aH) to check
the actual limits.

-- 
Glynn Clements <glynn@gclements.plus.com>

RE: Unable set the priority for a pthread through pthread_setschedparam

[Srinivas G.]

Glynn wrote:

> > domain       type    item     value
> > #@srinivasg  soft    rtprio   100
> 
> First, as Ben says, you must uncomment the line. Second, you may also
> need to set the hard limit. You can use "ulimit -a" (or -aH) to check
> the actual limits.

Thanks Glynn.

I am able to run the programs as a normal user after setting the soft as
well as hard values in /etc/security/limits.conf values. However,
without setting the hard limit, I am not able to run the programs. So,
by setting the soft and hard values to 100, I am able to run.

domain       type    item     value
@srinivasg  	 soft    rtprio   100
@srinivasg   hard    rtprio   100

Thanks for the right information.

With Regards,
Srinivas G