Il 04/06/2017 08:02, Bo Berglund ha scritto:
But I also have other systems where a real time system would be handy.
Do you have more info on this?
Yes. There was a bug in the way the FIQ was handled in a multicore ARM
CPU (i.e. RPi2 and RPi3) , which was causing random freezes, not much
frequent with vanilla kernels, but much more frequent with an RT_PREEMPT
kernel.
Finally someone (Oussama Ghorbel) took care of this and provided a patch.
Now at the OSADL (Open Source Automation Development Lab) Realtime QA
Farm a system is under test with an uptime of 173 days, which makes it
promising.
You may download kernel and patches from their website:
https://www.osadl.org/Profile-of-system-in-rack-7-slot-3.qa-profile-r7s3.0.html?shadow=1
I did it and it works just fine.
Another workaround for the problem can be disabling the Fast Interrupt
Queue in the command line, playing with kernel parameters. You can find
more details in:
https://www.raspberrypi.org/forums/viewtopic.php?f=29&t=159170&p=1094375#p1094375
Then, if you're new to real time under Linux, you might find handy our
Real Time Framework (YRMX), which provides a sort of high level
interface, robust, efficient, easy to exploit and now also fpc
compatible, to the pthread library. You'll find a description, both in a
pdf paper and pdf slides at:
http://www.copeca.it/OSADL/
Feel free to ask if you have more questions, or if you're interested in
YRMX. It's GPL'd but not yet published.
Giuliano
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