Re: Runtime Error with gnat 3.10p

[Markus Kuhn <Markus.Kuhn@cl.cam.ac.uk>]

David C. Hoos, Sr. wrote:
> >does anyone have an idea what the following little message is about :
> >Failed Runtime Assertion : GNULLI failure---Set_Priority
> >
> >Note that this showed up after executing a compiled Ada program
> >containing several tasks (instantiated task types)
> >This is on RedHat-Linux.

> One of the runtimes requires root privileges to do tasking while the
> other does not (I forget which is which).

Under Linux, the RM Annex D real-time task priorities can only be fully
implemented on top of POSIX.1c threads if the process is running with
root privileges. Otherwise, a malicious non-root process could lock-up
the entire system by requesting FIFO_Queuing and going into an
endless loop (in other words, you do not want full Annex D
compliance for normal untrusted users on a multi-user system).

Make sure you use the rts-fsu and not the rts-native run-time
library system, i.e. set the links in the gcc-lib/i386-linux/2.7.2.1/
subdirectory accordingly as described in the gnat install
documentation, unless you work on a special time-critical
application.

See also "man 2 sched_setscheduler" for the underlying C system call
and its restrictions.

Markus
(who wrote sched_setscheduler() back in the Linux 1.3 kernel :)

ftp://ftp.informatik.uni-erlangen.de/local/cip/mskuhn/misc/linux-posix.1b

-- 
Markus G. Kuhn, Security Group, Computer Lab, Cambridge University, UK
email: mkuhn at acm.org,  home page: <http://www.cl.cam.ac.uk/~mgk25/>