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
