Linux Mint / LinuxCNC 2.8.0 freezing - SOLVED?

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23 Aug 2021 15:37 #218522 by Muzzer
I'm being plagued by my Linux PC hanging up randomly, freezing the screen and mouse. The only remedy is to a hard reboot.

Although it may not be directly caused by LinuxCNC, it's a bit of an issue for a machine controller and isn't helping me to set up my LinuxCNC machine. Is there a recommended debug tool or any log files I can refer to to give me an idea what could be causing it?

I've managed to see this issue without LinuxCNC running but it's much more frequent when it IS running. This is a new, clean installation with very little by way of additional programs etc apart from Visual Studio Code and VNC client. I have a 5i25, 7i76 and 7i85 which all seem to be working as intended.

Any helpful suggestions as to how I can find and fix the root cause would be very gratefully received!

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23 Aug 2021 17:25 #218531 by tommylight
Open the PC and give it a thorough cleaning, remove the CPU cooler, clean it up, find some silicone paste for it and re-seat the cooler.
Failing power supply can also do that.

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23 Aug 2021 21:16 #218551 by Muzzer
It's a brand new motherboard with passive cooled, embedded processor, so the PSU sounds like the most likely culprit then. I have one of those Chinesium 12V powered modules that plugs directly into the mobo socket. 'Nuff said - time to get a different one perhaps. Must admit, although it's not proven yet, this was my prime suspicion.

Any recommendations for a robust 12V PSU module? The mini ITX case has an external 12V PSU and no much space left inside.

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23 Aug 2021 22:23 #218556 by tommylight
No recommendations as i never used them, once i needed it i made one and luckily it is still working after nearly 2 years ! :)
Check with palm on cooler after 5 to 10 minutes of use (if it survives), if you can not keep it on = add a fan.
Other stuff causing that type of issue are memory or memory controller so if you can do check that.

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24 Aug 2021 15:35 #218626 by Muzzer
I guess I could remove each of the 2 memory sodimms one at a time to see if that helps, also run the memory tests.

I've ordered a picoPSU from a reasonably reputable supplier which will hopefully eliminate that as a contender.

Thanks

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27 Aug 2021 16:36 #218919 by andypugh
Which kernel are you running?

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27 Aug 2021 17:49 #218925 by Muzzer
I don't know how to check for sure but it's a vanilla 2.8.0 install which presumably means it's running RTAI from what I can see. I haven't done anything unconventional unless by mistake. I simply installed the default setup, then got Probe Basic Lathe running. I've since (this week) got gmoccapy running as PB still seems to have some distance to go before it's finished but the issue was there before I got that far.

I don't actually need to start LinuxCNC to get it to freeze up. Does the kernel only get run when LinuxCNC starts?

None of the crash logs seem to tell me much of use, possibly because there is so much in them. I'm trying to figure out how to provoke the problem consistently so I stand a better chance of knowing if I've influenced it at all. I'm planning to remove the PC from the cabinet and run it standalone until I figure this out.

I had a job getting it to boot up initially, which seems to have been something to do with sleep states. However, now it simply freezes up, screen, mouse, kbd and all at random times. I can be running almost any kind of operation at the time. Time to freeze seems to be anything from 5 minutes to 30 hours.

Intermittent faults are the worst sort, as you can never be 100% certain you've fixed them....

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27 Aug 2021 18:34 #218930 by andypugh
If it’s a conventional Mint install then it is probably premmpt-rt

uname -a

Will tell you.

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27 Aug 2021 18:50 #218933 by Muzzer
Looks as if you were right:
muzzer@LinuxCNC:~$ uname -a
Linux LinuxCNC 4.19.106-rt46-lcnc #1 SMP PREEMPT RT Mon Sep 14 12:23:06 AEST 2020 x86_64 x86_64 x86_64 GNU/Linux


Does the kernel only run when you start LinuxCNC?


I was reading this from the downloads page which seemed to suggest RTAI:LinuxCNC 2.8 Downloads The Debian 10 Buster ISO uses a PREEMPT-RT patch which is close to mainstream Linux but does not, in some cases, give quite such good realtime performance as the previous RTAI kernel. It is very often more than good enough. It should probably be the first version tried even if using a parallel port. This is compatible with all Mesa and Pico interface boards.
  • LinuxCNC 2.8.0 Debian 7 Wheezy RTAI
Users requiring a known-stable RTAI installation can install the  Debian 7 Wheezy ISO  and then upgrade as described in  2.8 documents .
  • LinuxCNC 2.8.2 Debian 10 Buster RTAI
The more adventurous can install the Buster ISO and then install the experimental RTAI kernel as described in  2.8 documents Raspberry Pi 4 Uspace compatible with Mesa Ethernet and SPI interface boards.

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27 Aug 2021 23:56 #218949 by tommylight

Does the kernel only run when you start LinuxCNC?

Nope, it runs pretty much from boot time.
LinuxCNC will use the real-time part of the kernel when active, so that will set the processor to higher frequency and do some other stuff that will end up heating the processor much more.
Try adding a fan, a used PC one or whatever you can find, see if that makes the time to lock longer or get rid of it altogether.

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