Philippe Gerum wrote: > On Sat, 2007-02-17 at 10:02 +0100, Jan Kiszka wrote: >> This is a stand-alone real-time library for printf services. It is >> embedded into the Xenomai user space part but actually doesn't depend >> on any Xenomai service, just using plain Linux POSIX. >> >> The librtprint API looks much like the printf(3) man page: > > [...] > >> Further features: >> o Explicit or on-demand thread buffer creation >> o Override of default buffer size and polling period via environment >> variables ("RT_PRINT_BUFFER" and "RT_PRINT_PERIOD") >> o Support for buffer names (useful for the following patch e.g.) >> o Target output stream can be specified for each print invocation >> o Breaks all builds except for x86 (missing ubarrier.h headers) :o) >> > > ubarrier.h is redundant. include/asm-*/atomic.h is already there for > such purpose.
Guess you mean Xenomai's atomic.h, not the kernel ones. I didn't realised that it is also used from user space already. OK, will #define something like xnarch_rmb/wmb (or xnarch_read_memory_barrier?) in that file instead. > >> The code is stuffed into src/rtprint for now as patch 2/2 will need this >> lib to be built before the skin libraries. Better suggestions are >> welcome though. > > I basically agree that we need to provide more > co-scheduler-based-rt-safe services, so a non-intrusive print out > support should be welcome. A few things more: Actually, rt-safe printing is independent of co- vs. native scheduling. Even with a fully preemptible kernel, the worst-case complexity of normal printf may not be acceptable. I think rt_printf is generally useful in real-time programs. > > - looking beyond print out, we will probably want to iron more ANSI > services in the future. In order to prevent API proliferation, let's > consider the hardened print out support as the beginning of some > libansi_rt service collection. I was already considering to include the TLSF memory allocator for real-time malloc/free into some Xenomai library, but there were still technical issues with its lacking 64-bit support e.g., preventing some quick-hack. What further services do you have on your radar? My impression is that there will not be a lot beyond printing and memory allocation. > > - the same way libpthread_rt shadows 1003.1c services to iron them over > a co-scheduler, we should do the same for the ironed ANSI services. In > that sense, there is no need for rt_printf, rt_vsprintf and so on, we > just need to shadow printf, vsprintf and friends the same way we did for > pthread_create and such for substituting the 1003.1c support. Again, API > proliferation, especially of non-orthogonal stuff, needs to be fought > now. The bonus is that we would not have to ask people to rely on crufty > preprocessor tricks in order to compile their code in either real-time > layers X3 is going to provide (i.e. I-pipe-based co-scheduler and native > preemption). This would be consistent with the all-time Xenomai's > mantra, i.e. "integrate as seamlessly as you can, don't get uselessly > peculiar". > Think of RTDM: we have transparent overloading with the POSIX skin, but all others use the explicit selection via rt_dev prefix. I forgot to mention this, but my plan was to apply the same pattern for librtprint services. I don't think we should overload every printf outside the POSIX skin's scope automatically. Well, at least for the native skin, which is in my opinion quite a lot about _explicit_ real-time programming, I would really prefer to keep it like it is even under Xenomai 3. Jan
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