Hi EBo,
>> I think that the spare time problem is a common ailment. Whatever
>> the case, with more people doing nothing more than watching this
>> thread, sooner or later a light bulb will go on and we'll have our
>> solution.
>
> true... Any more ideas?
Yep! I discovered the 'record' feature in gdb. Start up gdb on
rtapi_app, then run the following:
start load threads name1=fast period1=50000
record
c
With period1=50k and the program running super-slow in gdb record mode,
there'll be lots of output about missed deadlines that'll be tickling
the bug in the background. If you're lucky, you'll get the segfault in
a chunk of actual readable C code (probably malloc(), so install the
debug symbol packages). Then you can muddle around until you find a
corrupted location, and set a 'watch -l <expression>'. Then run the
program backwards with 'reverse-continue' until you find some other
place that's writing to that location, but shouldn't.
That's as far as I've gotten, but it seems like a promising technique.
However, it may take some iterations. My first results lead me to the
'memset' line in linux_rtapi.c. It appears that malloc(stacksize) is
handing out memory already allocated. I assume that means the malloc
data structures are already corrupt at this first point, but to back up
through the next iteration I still need to muddle through *what* is
corrupt, since 'watch' can only examine a single memory location and
there can only be four watch points at any time.
If anyone needs more details to replicate this, I'm happy to provide.
It's quite a learning curve for me.
> I've got some of Li's NURBS hardware for testing, and as soon as I am
> caught up at work the plan is to set up a Gentoo portage overlay that
> loads/partial-preconfig of an appropriate
> RT-Preempt/LinuxCNC-EMC2/latency-tools/... Note: I had some old ebuilds
> for RT-Linux, RTAI, EMC2, EMC2 in the distant past...
Neato! Keep us in the loop.
Does anyone still use RT-Linux? I seem to remember it hasn't been
updated for recent kernels, but I also know of (non-machine) shops that
still run Linux 2.4.x for whatever reason.
John
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