Hi Andy,
>> The closest I got was to compile mathtest.c as though it were a
>> kernel module. That failed during compile, since floating point
>> operations are disallowed in the kernel (they use the SSE register,
>> which must stay clean for userspace),
>
> Is that an RT-Preempt limitation? There are lots of FP operations in
> kernel modules elsewhere in LinuxCNC.
> However, you might need to use the realtime-safe functions from rtapi_math.h
Well, my experience with the kernel is that of a rank amateur, and more
embarrassing, what I said about disallowing the SSE register is probably
wrong: I think I came across a freebsd thread and wasn't paying attention.
However, the kernel makefiles use the gcc options '-mno-sse' and
'-mno-sse2' to turn off those extended instructions sets in my setup.
It could be an rt-preempt thing, or anything else for all I know right now.
This question will surely need to be addressed properly before LinuxCNC
on rt-preempt works, so I'll next take a look to see how RTAI solves the
problem. You're surely right that rtapi_math.h will be key.
John
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