rtapi -- uspace -- "Using POSIX non-realtime"

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9 years 11 months ago - 9 years 11 months ago #83079 by dgarrett
I looked some more and it seems that the uname -a report for
your custom debian stretch kernel:
Code:
latheoperator@125cnc:~$ uname -a Linux 125cnc 4.8.9-jbc01 #1 SMP PREEMPT Sun Nov 20 09:34:59 CET 2016 x86_64 GNU/

does not comply with a test in src/rtapi/uspace_common.h
Code:
static int detect_realtime() { struct utsname u; int crit1, crit2 = 0; FILE *fd; uname(&u); crit1 = strcasestr (u.version, "PREEMPT RT") != 0; if ((fd = fopen("/sys/kernel/realtime","r")) != NULL) { int flag; crit2 = ((fscanf(fd, "%d", &flag) == 1) && (flag == 1)); fclose(fd); } return crit1 && crit2; }

Your kernel is reporting "SMP PREEMPT without the specific
substring expected, namely: "PREEMPT RT".
So it appears no preempt-rt patch has been applied to the kernel you are using.

On a system i use (jessie,uspace), the report is:
Code:
Linux t520 4.1.0-0.bpo.2-rt-amd64 #1 SMP PREEMPT RT Debian 4.1.6-1~bpo8+1 (2015-09-09) x86_64 GNU/Linux

ref (2.7 tree):
git.linuxcnc.org/gitweb?p=linuxcnc.git;a...d8;hb=refs/heads/2.7
Last edit: 9 years 11 months ago by dgarrett.

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9 years 11 months ago #83080 by PCW
I dont even think there is RT a patch for 4.8.9

AFAIK 4.8.6-rt5 is the latest as of Nov 21,2016

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9 years 11 months ago - 9 years 11 months ago #83081 by jCandlish
Thanks!

Somehow I thought PREEMPT RT was in mainline. I checked, and no patch is yet available for 4.8.9

...

Anyway, the servo thread jitter I am seeing with a celereon skylake system is quite disappointing. >= 100μs.

image missing http://gallery.candlish.net/_data/i/upload/2016/11/21/20161121163945-7b29ab3e-me.png

I question if it is sufficient?

This is with

GRUB_CMDLINE_LINUX="ipv6.disable=1 intel_idle.max_cstate=1 processor.max_cstate=1"


I've looked also to 'powertop' and 'i7z' for insight on this jitter, but no joy.

.
Last edit: 9 years 11 months ago by jCandlish.

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9 years 2 months ago #97743 by thuwrx10
One should remember to execute 'sudo make setuid' after compilation. Otherwise still not able to use POSIX realtime

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5 years 7 months ago #203152 by V-max
Hi,
I have the same problem in a: Debian 10 4.19.0-14-rt-amd64 kernel.
Where can I check the last patch available?
Thanks a lot!

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5 years 7 months ago #203173 by andypugh
Are you sure that you have the same issue as this thread is discussing?

Did you compile the RT kernel yourself? (And, if so,. why?)

Did you compile linuxCNC yourself? (and, if so, why?)

What does uname -a say?

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