Schooner and Robert,

OK, here is what I see when I run those tests. Rather than grep the results of 
uname -r, I just printed out uname -r. 

machinekit@beaglebone:~$ cat /sys/kernel/realtime
cat: /sys/kernel/realtime: No such file or directory
machinekit@beaglebone:~$ cat /boot/config-4.19.23-bone-rt-r22 | grep 
CONFIG_PREEMPT_RT_FULL=yes
machinekit@beaglebone:~$
machinekit@beaglebone:~$ uname -a
Linux beaglebone 4.19.23-bone-rt-r22 #1stretch Sat Feb 16 22:07:49 UTC 2019 
armv7l GNU/Linux


Actually looking at /boot/config-4.19.23-bone-rt-r22 here is what I found with 
respect to CONFIG_PREEMPT_*
CONFIG_HAVE_PREEMPT_LAZY=y
CONFIG_PREEMPT_NONE=y
# CONFIG_PREEMPT_VOLUNTARY is not set
# CONFIG_PREEMPT__LL is not set
# CONFIG_PREEMPT_RTB is not set
# CONFIG_PREEMPT_RT_FULL is not set

Even though machinekit “runs” i.e., starts up, it is clear that rt-preempt is 
not configured correctly to run machinekit in realtime. I can’t run my linux pc 
at the moment to look at how that config should be set, but I believe that at 
the very least these changes should be made

# CONFIG_HAVE_PREEMPT_LAZY
# CONFIG_PREEMPT_NONE
# CONFIG_PREEMPT_VOLUNTARY is not set
# CONFIG_PREEMPT__LL is not set
# CONFIG_PREEMPT_RTB is not set
CONFIG_PREEMPT_RT_FULL=y 

Thanks,
Alan

> On Feb 19, 2019, at 1:42 AM, [email protected] wrote:
> 
> That is one way to deal with it.
> rtapi_compat.c first checks the env var FLAVOR, before trying to determine 
> other ways
> 
> Run these tests from a terminal and let us know what result you get
> 
> cat /sys/kernel/realtime     (should return 1)
> cat /boot/config-<kernel-version>  | grep CONFIG_PREEMPT_RT_FULL=yes  ( 
> should return CONFIG_PREEMPT_RT_FULL=yes)
> uname -a | grep 'PREEMPT RT'  ( should  return PREEMPT RT - but we already 
> know it won't)
> 
> There is something screwy about the 4.19 kernel and rt.  I stopped using the 
> Debian rt-amd64 version and reverted to 4.18 because of problems
> 
> 
> On 19/02/19 04:44, mugginsac wrote:
>> Robert just furnished a new test image. It definitely has an rt-preempt 
>> kernel, when I exported FLAVOR=rt-preempt, it ran machinekit.
>> However, before I exported FLAVOR=rt-preempt, machinekit tried to run the 
>> posix realtime stuff (term of art).
>> 
>> So, the question is how does machinekit try to determine the nature of the 
>> kernel that it is running on?
>> 
>> Robert asked if we should just set FLAVOR=rt-preempt in the environment when 
>> we create the uSD. Is that acceptable?
>> 
>> 
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