Cedric Herreman wrote: > Hello, > > I am porting a 2.4 RTAI kernel module to Xenomai 2.0 kernel 2.6. I used > some basic math functions in the original module. This is posing problems > for me now. > > In the module source i include <math.h>. I add -I/usr/include to the > compiler flags and also "-ffast-math -mhard-float". > > If i compile this, i get warnings about double definitions of > "__attribute_pure__" and "__attribute_used__". > > If i insert the kernel module, i get an error message : > "Xenomai: Invalid use of FPU in Xenomai context at " + probably the address > of the instruction where the math function is called. > > Can anyone give me a hint ? Thanks.
You can only use floating point operations from real-time threads contexts, not from module initialization and finalization routines, and you have to signal Xenomai, when creating kernel space real-time threads, that the thread will be allowed to use FPU. For the RTAI skin, this is what the rt_task_init function 6th argument is for. There is currently no math library module in Xenomai. So, the answer is that you have to avoid math functions, or make a xeno_math module, the way it is done in RTAI, i.e. using a math library such as the one made by Sun and used by FreeBSD, or one among the various libcs available. We once discussed this with Philippe, and a good candidate seemed to be newlib at that time: http://sourceware.org/newlib/ Looking at newlib sources, it seems that some of its contents come from the Sun library too. -- Gilles Chanteperdrix.
