Hello Gene, There are many things related to udev and systemd that can cause interruptions for excess of 200 ms. (This is one of the main reasons that I refuse to use a desktop type OS on a machine that is cutting on a $20,000 casting.) It is also why I refuse to allow a full keyboard to be connected. All it takes is someone to hit <SysReq><Ctrl>b (or something similar), and it is all over unless you do some serious configuration to the kernel and a dozen other daemons. I am considering dropping the majority of HID support from my distro to block things like mice and keyboards. My setup is intended to work only with a touch screen and on screen keyboard. I have never had any success whatsoever using a mouse in my shop, there is just way too much dirt, chips, coolant, oil and clutter to make this happen. (I made the mistake of leaving my laptop near a machine for about 5 minutes, and I had to spend the rest of the day cleaning aluminum chips and coolant out of it.) As I mentioned earlier, I intend to solve the USB storage issue by not allowing any USB storage devices to be mounted when Linuxcnc is in any other state than "off". -Neil-
On Thu, Dec 31, 2015 at 10:16 AM, Gene Heskett <[email protected]> wrote: > On Thursday 31 December 2015 12:26:01 Neil Whelchel wrote: > > > Hello Tom, > > It is my own A20 board design. I could not find anything (cheap) that > > has open drain drivers that can handle 5 amps, along with protected > > inputs and a FPGA. I made the board specific for realtime automation. > > > > I call the distro LinuxInside. It is built from source. It uses opkg > > to distribute files. I use scripts, patches, and programs from many > > places, Debian, OpenWRT, Mikrotik, Gentoo, OpenDesktop and others. It > > has custom startup and shutdown programs that are application > > specific. The instance that I am using for Linuxcnc is using systemd > > at the moment, but I may change that. Part of the problem is related > > to udev. When a USB device is plugged in, udev receives messages from > > the kernel which may cause modules to be inserted. This is highly > > likely to cause an interruption of the realtime services. Part of the > > plan is to modify udev to watch the state of Linuxcnc and only take > > actions when the machine is in "off" state. There are a number of USB > > modules that can block things as well, so I will likely only include > > very limited USB support for things that are directly required for > > Linuxcnc like USB flash drives, buttons, shuttles, and such. -Neil- > > > > > Don't forget that both keyboards and mice are (generally) wireless AND > USB these days. In my experience it was storage devices with a USB > interface, like USB keys that play hell with the realtime. It seems the > filesystem scans them about every 5 seconds, and does it with the IRQ's > locked out for 200 milliseconds or more. > > ------------------------------------------------------------------------------ _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
