We are moving towards POSIX "minimal RT system" compliance.
On Sun, May 23, 1999 at 04:19:14PM -0400, Vladimir G Stanishev wrote:
> On Sun, 23 May 1999, Juanjo Marin wrote:
>
> > Hi Hosam,
> >
> > You can find more information about Linux and POSIX.4 (POSIX 1003.1b after
> > the big renumbering) in the following url:
> > ftp://ftp.informatik.uni-erlangen.de/local/cip/mskuhn/misc/linux-posix.1b
> >
> > One thing that you have to take into account is the fact that POSIX.1b is
> > structured as a set of options that a vendor can support or not. Only some
> > functions are compulsory to say that a system is POSIX.1b compliant (If 'm
> > not wrong these options are the queue signals and not much more).
> >
> to add another word of caution is that support for POSIX.1b options
> does not necessarily mean that the system is good for hard real time.
> especially with Linux. the options NOT supported so far are
> _POSIX_TIMERS (not implemented)
> _POSIX_PRIORITIZED_IO (not implemented)
> _POSIX_MESSAGE_PASSING (not implemented - that's for message queues)
> _POSIX_SHARED_MEMORY_OBJECTS (not implemented)
>
> all other options (see that paper above or the book below) are
> supported in teh new kernel 2.2.x with glibc-2.1. posix semaphores are
> partially supported. the missing options in teh previous kernel are
> real time signals I think. and that's not to say that other non posix
> options are not there for message queues or shared memory (system V).
>
> and a last note is taht the use of RTLinux forfeits tha LINUX support for
> POSIX since it's all part of LInux whihc is now a low priority process.
> Some POSIX.1b calls seem to be implemented as part of RTLinux in that new
> beta version for 2.2.9 but taht too appears to be a work in progress.
>
> > RTLinux, as far I know, is not a POSIX way but is a REAL way to get a RT
> > system working. Another POSIXish alternative is QNX (www.qnx.com) for
> > example, but it's commercial.
> >
> > Finally, if you're interested in the POSIX way I strongly recommend the
> > following book "POSIX.4: Programming for the real world, Bill O.
> > Gallmeister, O'Reilly & Associates, 1995"
> >
> > best regards,
> >
> > Juanjo
>
>
> - Vladimir
>
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