| Title: | DIGITAL UNIX (FORMERLY KNOWN AS DEC OSF/1) |
| Notice: | Welcome to the Digital UNIX Conference |
| Moderator: | SMURF::DENHAM |
| Created: | Thu Mar 16 1995 |
| Last Modified: | Fri Jun 06 1997 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 10068 |
| Total number of notes: | 35879 |
A SW partner has snet us a question in an area we don't have experience
in supporting, so I am hoping for some help regarding the following
issue with the priocntl() call.
I have already asked him for the OS rev, and whether he has the SYSV
environment installed which is not clear from the attached note.
Thanks,
Jeff Kenyon
I'm trying to use priocntl to change my process's scheduling class to
real-time. I run the program under root but receive errno 35 (EAGAIN) when
priocntl is called with the PC_GETCID command. In this call, I am trying to
obtain the class ID for the "RT" (real-time) scheduling class. Once I have
the class ID, I can then re-issue the system call with the PC_SETPARMS
command to change the scheduler class. Here's an extract of all applicable
source code from my program:
#include <sys/priocntl.h>
#include <sys/rtpriocntl.h>
pcinfo_t sinfo;
pcparms_t sparms;
rtinfo_t *rtinfo;
rtparms_t *rtparms;
strcpy (sinfo.pc_clname, "RT");
rc = priocntl (0, 0, PC_GETCID, (caddr_t) &sinfo);
if (rc != 0)
{
fprintf(stderr, "ERROR: PD: System call priocntl returned: = %d\n", errno);
}
The EAGAIN errno is described as follows by the priocntl man page and makes
it sound as if something isn't configured in the kernel:
[EAGAIN] An attempt to change the class of a process failed because of
insufficient resources other than memory (for example, class-
specific kernel data structures).
By replacing the fourth argument with a null pointer, the priocntl system
call returns a 5 indicating there are 5 scheduling classes defined (right?).
I've talked with our system administration staff and they have verified that
real-time preemption has been enabled in the kernel. Is there something
we're missing? Any help you could provide would be greatly appreciated.
| T.R | Title | User | Personal Name | Date | Lines |
|---|---|---|---|---|---|
| 9329.1 | SMURF::DENHAM | Digital UNIX Kernel | Fri Mar 28 1997 17:19 | 10 | |
Jeff,
priocntl has got to be the most horrendously arcane api ever, ever
invented. It worse even than the system V semaphore and message
apis.
That said, I'll try out the test program and figure out what's
up. You might consider filing a problem report for tracking this,
but you can certainly wait till I confirm this isn't user
error and not my error....
| |||||
| 9329.2 | thanks | HYDRA::KENYON | The Foundation of Science...Fiction | Fri Apr 04 1997 11:21 | 5 |
Thanks -- any status as of today?
thanks,
-jeff
| |||||
| 9329.3 | SMURF::DENHAM | Digital UNIX Kernel | Fri Apr 04 1997 14:00 | 2 | |
It's still in the to-do list but moving up. Hasn't been a good week or so
for this sort of investigation...
| |||||
| 9329.4 | SMURF::DENHAM | Digital UNIX Kernel | Mon Apr 07 1997 12:10 | 53 | |
OK, tried it. Cut the bits out of the base note, added a few missing
variables, and ran the problem. No problem, as root or as a
regular user.
I get back 5 as a return value (number of classes), and sifno.pc_clname
comes back as "RT".
Does they customer have all these defs in his config file?
#
# Standard options.
#
options UNIX_LOCKS
options SER_COMPAT
options RT_PREEMPT
options RT_SCHED
options RT_SCHED_RQ
options RT_PML
options RT_TIMER
options RT_SEM
options RT_CSEM
options RT_IPC
The one that really matters for priocntl, is RT_SCHED_RQ. If it's
not defined, I believe you'll get back EINVAL, no EAGAIN.
If fact, I can't find anywhere in the GETCID code path where
EAGAIN can be returned. Have they confirmed that this
code fragment alone fails on there test system?
#include <stdio.h>
#include <sys/errno.h>
#include <sys/priocntl.h>
#include <sys/rtpriocntl.h>
main()
{
int rc;
pcinfo_t sinfo;
pcparms_t sparms;
rtinfo_t *rtinfo;
rtparms_t *rtparms;
strcpy (sinfo.pc_clname, "RT");
rc = priocntl (0, 0, PC_GETCID, (caddr_t) &sinfo);
if (rc != 0) {
fprintf(stderr, "ERROR: PD: System call"
" priocntl returned: = %d, errno %d\n", rc,
errno);
}
printf("Class name: %s\n", sinfo.pc_clname);
}
| |||||