linux 4.1.195 issue

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18 Jul 2021 15:54 #215231 by crowloy
linux 4.1.195 issue was created by crowloy
I installed 4.1.195 kernel from source with the latest rtai patch. configuring linuxcnc for uspace due to not being able to use the rtai since I have a 7i92 board, I find that I get ALOT of watchdog error's on the 7i92 to the point of being absolutely useless. linux is set for low-latency desktop on a I5 processor. Is anyone else seeing this?

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18 Jul 2021 15:57 #215232 by PCW
Replied by PCW on topic linux 4.1.195 issue
The "Low Latency Desktop" is not real time, you need to select
"Fully Preemptable Kernel"

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18 Jul 2021 16:46 #215239 by crowloy
Replied by crowloy on topic linux 4.1.195 issue
that doesn't appear to be an option though.

No Forced Premption (Server)
Voluntary Kernel Premption (Desktop)
Preemptable Kernel (Low-Latency Desktop)

These are the only options available.

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18 Jul 2021 21:01 #215255 by PCW
Replied by PCW on topic linux 4.1.195 issue
That suggests that you did not apply the real time patches

Is there any reason you are not using the latest LinuxCNC (2.8.2) ISO?

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19 Jul 2021 00:06 #215269 by crowloy
Replied by crowloy on topic linux 4.1.195 issue
I applied the rtai 5.3 patches to a bare 4.1.195 kernel. Then did the make oldcconfig and make menuconfig to enable an option for rtai. i wasn't aware I needed to install the rt patch on top of all of this.

As for the 2.8.2 iso, I started with linux mint 19, installed pathpilot 2.0 on it. I have since upgraded that to 2.7 I believe. I run linuxcnc 2.8.2 on a separate account with qtplasmac for my plasma table. Pathpilot is used for my milling machine. I need to look into setting up qtdragon, as I can't stand the look of gmocappy or axis.

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19 Jul 2021 00:27 #215274 by PCW
Replied by PCW on topic linux 4.1.195 issue
Yes, you need to apply the Preempt-rt patches that match the exact kernel you are using. 4.1.195 doesn't have such patches so I would probably choose the latest of the 4 series kernels with a RT patch = linux-4.19.196

Building the kernel would be something like this:


cd ~
sudo apt-get update
sudo apt-get install build-essential bin86 libssl-dev bc libelf-dev bison flex libqt4-dev libncurses5-dev pkg-config
mkdir rtlinux
cd rtlinux
wget www.kernel.org/pub/linux/kernel/v4.x/linux-4.19.196.tar.xz
wget www.kernel.org/pub/linux/kernel/projects...19.196-rt83.patch.gz
tar -xpf linux-4.19.196.tar.xz
gunzip patch-4.19.196-rt83.patch.gz
cp patch-4.19.196-rt83.patch linux-4.19.196
cd linux-4.19.196
cat patch-4.19.196-rt83.patch | patch -p1
make xconfig
make -j4
sudo make modules_install
sudo make install
The following user(s) said Thank You: arvidb

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19 Jul 2021 09:33 #215300 by rodw
Replied by rodw on topic linux 4.1.195 issue
Whilst PCW's recipe above got me onto the PREEMPT_RT kernel about 5 years ago, there is little reason to do it today as there are patches available which can apply the kernel without compilation.
Tommy does a good job documenting the process forĀ  Mint 19.3 here
forum.linuxcnc.org/9-installing-linuxcnc...nd-easy-installation
It works and can be done in minutes not hours.

But being able to compile the kernel is pretty cool :)

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20 Jul 2021 21:41 #215444 by crowloy
Replied by crowloy on topic linux 4.1.195 issue
I've been compiling linux kernel's since the early to mid 90's. I even have my moment of fame mentioned in the kernel source. I was just looking at the differances between rtai from rtai.org and rt patches from linux.org. linuxcnc has both mentioned in the configure, so I was trying it out. I misspoke about the system running my plasma. it's actually and I3, but has terrible latency issues..
The following user(s) said Thank You: rodw

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