On Tue, 2011-02-08 at 13:51 +0100, Henri Roosen wrote: > On Tue, Feb 8, 2011 at 1:31 PM, Gilles Chanteperdrix > <[email protected]> wrote: > > Philippe Gerum wrote: > >> On Tue, 2011-02-08 at 13:16 +0100, Gilles Chanteperdrix wrote: > >>> I was not talking about the Xenomai case specifically, but since Henri > >>> would like to have the full signals implementation with Xenomai, this > >>> does a apply to Xenomai too. > >>> > >>> > >> > >> I think we all agree that having a complete signal implementation for > >> Xenomai in pure rt mode won't happen overnight. So the point is now: how > >> could it be mimicked, at least for the most useful part. > >> > > > > My point is that whatever you do, a switch user-kernel, then kernel-user > > is not going to be lightweight, so avoiding it in the application in the > > first place may be a better idea. > > > > My aim with implementing complete signals was rather for things like > > timer_* and mq_notify, where the interface requires them, I did not even > > imagine implementing SIGFPE, SIGILL, SIGTRAP, which I thought could not > > be time critical anyway, for the reasons explained earlier. So, my > > question (rather to Henri) is: what would we need SIGFPE, SIGILL, > > SIGTRAP in an real-time application for? > > I agree it might be unusual. For the tracing use case: the SIGTRAP we > use as a means for tracing whether code is actually executed, just > like breakpoints, we exchange the code to 0xcc and handle the > exceptions do book-keeping but don't stop the task. We know this has > overhead, it also had when using our old OS. The old OS handled it in > an accepted amount of time. Using the Xenomai kernel it also works, > however the overhead is not acceptable anymore. > Installing a floating point exception handler was also provided to our > customers with the old OS and we have to make that available now too. > So actually it is all because of legacy reasons, we have to provide > similar functionality as with the old OS. > > I'm afraid we cannot mimic enough so it suits our use cases. We need > the fault context to handle the exception and to set the IP one > instruction back.
So you need the signal rebase over the mayday support I merged a few months ago. Back to square one I'm afraid, this won't be available soon, albeit this might happen in the 2.6 timeframe. We'll see. > > Thanks, > Henri. > > > > > -- > > Gilles. > > -- Philippe. _______________________________________________ Xenomai-help mailing list [email protected] https://mail.gna.org/listinfo/xenomai-help
