Philippe Gerum wrote: > On Wed, 2007-08-29 at 16:32 +0200, Jan Kiszka wrote: >> Markus Osterried (BA/EDD) wrote: >>> Hi, >>> >>> it seems that in the RTDM API, all the timeout functions which use >>> nanosecs_rel_t have a strange behaviour. >>> The timeout in nanoseconds is converted to ticks and the number of ticks >>> is rounded down. So when we want to wait e.g. 500000 nanoseconds and the >>> timertick is 1 ms, xnpod_ns2ticks() rounds down to 0. But 0 is the >>> special value RTDM_TIMEOUT_INFINITE, so we wait forever. I use Xenomai >>> 2.3.1, but I think it's basically the same in trunk. >> It should even impact other skins as well when in tick-based timing >> mode. I would bet more users of xnpod_ns2ticks() may have overseen this >> rounding issue - like RTDM did. >> > > Other skins may only mean POSIX and native, since the other ones only > deal with ticks.
Ah, yeah, of course. POSIX is safe because it does well-defined rounding on its own. Native itself has no problem, just the user may get informed about the rounding behaviour of rt_timer_ns2ticks. Otherwise, things like rt_sem_p(sem, rt_timer_ns2ticks(some_nanos)) may unexpectedly behave like RTDM does now. > >>> Wouldn't it be better to round up the ticks instead of round it down? >> Hmm, probably. Mind to work out a patch for xnpod_ticks2ns()? >> >> What do others think about this issue? Can/should we change the rounding >> behaviour at nucleus level? >> > > Clearly not. You don't change the core rounding policy for fixing > shortcomings in the higher levels, especially to fix invalid application > requests. I do want to be able to round down at nucleus level, which I > would not be able to do anymore with a rounding up policy at core level. > This change belongs to the skin which wants this behaviour. Agreed, we primarily need to fix RTDM here. But what about introducing generic xnpod/xntbase_ns2ticks_floor/ceil() for this? Would avoid more re-inventions of this common service. Jan
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