On Tue, Jun 28, 2022 at 01:04:29AM +0100, andy pugh wrote:
> Trying to address a recent request to add latency-histogram to the
> menu, I have attempted to build a .deb
>
> But my previous recipe (./debian/configure -r ) no longer works.
>
> All my test machines (at the moment) are running an RTAI kernel.
>
> Have we actually abandoned support for this whilst I was not looking?
Yes, I made a commit to remove kernel-rtai and xenomai support from
debian/configure. I think that subsequent to mailing this you also
re-found the PR where this was discussed at the time:
https://github.com/LinuxCNC/linuxcnc/pull/1175
You stated your preference at the time to not make the change and I
didn't listen. I apologize, because I should not have acted so
unilaterally, and regret the extra work it's creating for you now.
I don't mind if it is re-added. A problem is, the low% chance of the
runtests failing end up leaving the buildbot broken for hours/days and
require seb's intervention each time. But if buildbot doesn't test it,
then it'll end up bitrotted anyway.
Personally, I'd hoped the path forward would be using rtai realtime from
uspace. It means LinuxCNC doesn't require any kernel modules, but
rather it can run on any Preempt-RT kernel and also any RTAI kernel
whose userspace API is compatible with the rtai-config script that was
found at configure time.
It's preferable to kernel-mode RTAI because there are no LinuxCNC kernel
modules and no extremely weird math library tricks for using math
functions and floating point inside the kernel.
Since the RTAI problems (which did affect my real system, not just
virtualized buildbot systems) occur when unloading rtai kernel modules,
an interesting fact about the lxrt approach is that it should not be
necessary to ever un-load the rtai modules after they are loaded, though
this is probably what the halrun/realtime code still does.
I wrote this and lightly tested it years ago, but it is far from ready
for actual use, due to lack of actual use. And of course I'm not able to
commit to working on it even if people bring me excellent bug reports.
It looks like configuring `--with-realtime=uspace` should try to pick up
rtai-config from standard locations, but of course this is likely to be
all bitrotted as well. I have no way to test from here, as I have no
RTAI systems.
Jeff
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