Philippe Gerum wrote:
> On Mon, 2007-02-19 at 00:31 +0100, Gilles Chanteperdrix wrote:
> > Jan Kiszka wrote:
> > > Hi Philippe,
> > >
> > > I just verfied that the mlockall issue persists. But it doesn't appear
> > > to be a regression anymore. This little posix demo exposes it now on
> > > both 2.6.20-1.7-02 and 2.6.19-1.6-06 against latest trunk:
> > >
> > > #include <stdio.h>
> > > #include <sys/mman.h>
> > > #include <pthread.h>
> > >
> > > int main(int argc, char *argv[])
> > > {
> > > struct sched_param param = { .sched_priority = 10 };
> > >
> > > // mlockall(MCL_CURRENT|MCL_FUTURE);
> > >
> > > pthread_setschedparam(pthread_self(), SCHED_FIFO, ¶m);
> > >
> > > printf("shouldn't be printed...\n");
> > > pause();
> > > }
> > >
> > >
> > > In contrast, the same done via the native skin (rt_task_shadow) triggers
> > > warning and program termination as expected.
> > >
> > > It looks to me like the temporary mlockall during libpthread_rt init is
> > > not really reverted (but munlockall is actually called) or not
> > > propagated to the mm state that is later checked on xnshadow_map.
> >
> > The problem is that the root thread is already shadowed in this program
> > when pthread_setschedparam is called. So, xnshadow_map is not called and
> > the flag is not checked.
> >
>
> Yep. This makes sense, since kernel-wise, sys_munlockall does clear the
> VM_LOCKED bit from the caller's mm default flags.
>
> Since this behaviour is specific to the POSIX skin because it silently
> shadows the main thread as a Xenomai thread from the SCHED_NORMAL class,
> maybe we should check the mm state in the POSIX thread creation routine
> too, when SCHED_FIFO or SCHED_RR are passed as the scheduling class.
The flag is checked if another thread is created, since xnshadow_map is
called. The only solution I see at the moment is to remove the call to
munlockall in the library initialization.
--
Gilles Chanteperdrix.
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