Sebastian, I made an issue on Monday that also speaks to this race condition that's been exposed by the recent iocontrol moves.
Here is the issue: https://github.com/LinuxCNC/linuxcnc/issues/2700 I am not sure if Rene is on the dev list, so it might be prudent to make these observations in the issue I created? If nothing else, it's tracked that way. Thanks, Greg On Wed, Oct 18, 2023 at 5:21 PM Sebastian Kuzminsky <s...@highlab.com> wrote: > When the `linuxcnc` script launches linuxcnc it starts Task, then loads > motmod (as one of the commands in the [HAL]HALFILE list). > > I believe this is racey, leading to at least some of the intermittent > failures on the buildbot. > > Task does this at startup: > > 1. Runs `usrmotInit()` which connects to the emcmotStruct shm, including > emcmotCommand and emcmotStatus. > > 2. Runs `usrmotWriteEmcmotCommand()` to copy the first initialization > command into emcmotCommand, then polls emcmotStatus waiting for motmod > to echo the first command's commandNum. > > 3. If the commandNum does not echo in emcmotStatus within a timeout, > Task gives up on the command. > > Motion/motmod does this at startup: > > 1. Runs `init_comm_buffers()` to connect to the emcmotStruct shm, > including emcmotCommand and emcmotStatus. Calls `memset()` on > emcmotStruct to initialize it to all-bytes-zero. > > 2. Start polling emcmotCommand for new commands (this happens in a hal > thread via the `motion-command-handler` function). > > The race happens when Task does its 1 and 2, then Motion does *its* 1, > discarding Task's first command. > > > I think the recent move of iocontrol into Task changed system timing and > made this race more likely to bite. > > Any thoughts? > > > -- > Sebastian Kuzminsky > > > _______________________________________________ > Emc-developers mailing list > Emc-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-developers > _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
