On Tue, 2007-06-12 at 08:42 +0200, M. Koehrer wrote: > Hi everybody, > > I want to know why the --enable-smp option for "configure" of Xenomai is used > when there > is already the corresponding option selected with the kernel configuration?
--enable-smp is only used when you want the user-space side to _require_ SMP support to be present into the running kernel; i.e. for some (weird) reason, your application really needs this. Xenomai libraries don't care whether SMP support is enabled or not, they are not sensitive to that issue (see the "weak" status of this option in README.INSTALL) I agree that this could be a bit confusing, I guess that the documentation needs an update to clarify this point. > In other words: > Isn't it possible to get the value from the kernel configuration to configure > Xenomai itself properly? No, we cannot anymore since v2.1, at least not at build time. The point is that we have totally decoupled the build processes between kernel and user-space supports. Having no build-time dependencies from the user-space libs on the internal structures we use in kernel space is what allows you to run older application binaries on newer Xenomai releases, unless we had to change the syscall ABI for some very good reason (which is seldom). The point is that we try hard to be friendly to people deploying Xenomai installs in the field, so that they don't have to always rebuild the whole stuff would they want to only upgrade part of their setup. There is a built-in ABI revision value dynamically shared between the kernel and user-space code at application startup to trap potential mismatches. > Or: What effects could result from a wrongly configured Xenomai (e.g. kernel > with SMP, > Xenomai configured without --enable-smp)? None, it would work, provided your application code does not depend on the SMP feature in some tricky ways it would be the only one to know about (again, Xenomai libs just don't care, there are no build-time dependencies on the kernel support here). > > Thanks for any answers on that questions. > > Regards > > Mathias > > -- Philippe. _______________________________________________ Xenomai-help mailing list [email protected] https://mail.gna.org/listinfo/xenomai-help
