Philippe Gerum wrote:
> On Tue, 2007-03-13 at 16:25 +0100, Gilles Chanteperdrix wrote:
> > M. Koehrer wrote:
> > > Hi all,
> > >
> > > I have a problem to catch segment violations with Xenomai:
> > > For demonstration I use the following program:
> > > ------------------------------------------
> > > #include <stdio.h>
> > > #include <sys/mman.h>
> > >
> > > #include <native/task.h>
> > > #include <native/sem.h>
> > > RT_TASK taska_desc;
> > > volatile int *pointer = 0;
> > >
> > > void mytaska(void *cookie)
> > > {
> > > int i;
> > > for (i=0; i < 50; i++)
> > > {
> > > rt_task_sleep(50000000);
> > > if (i > 20)
> > > {
> > > *pointer = 123;
> > > }
> > > printf("Hello %i\n", i);
> > > }
> > > printf("Hi, this is task A\n");
> > > }
> > >
> > > int main(void)
> > > {
> > > mlockall(MCL_CURRENT|MCL_FUTURE);
> > >
> > > rt_task_create(&taska_desc, "mytaska", 0, 81, T_JOINABLE);
> > > rt_task_start(&taska_desc, &mytaska, NULL);
> > >
> > > rt_task_join(&taska_desc);
> > > printf("Main: A joined\n");
> > >
> > > return 0;
> > > }
> > > ---------------------------------------
> > > Whenever i is greater than 20 a segment violation occurs, as I must not
> > > write
> > > to address 0 (the pointer is always NULL).
> > > However, what happens is, that my system freezes after printing out 18
> > > or 19.
> > > I have to reset the PC to continue.
> > > When I write a printf() directly before the invalid assignment I get the
> > > usual linux
> > > "segmentation fault" error message.
> > >
> > > How can I catch a signal in a Xenomai real time task?
> > >
> > > I am running Xenomai 2.3.0 + NOCOW patch.
> > >
> > > I have enclosed the .c file and a Makefile in a .tgz file.
> > >
> > > Thanks for any feedback on that issue
> >
> > It looks like the "relaxing a kicked thread" issue again. Could you try
> > the attached patch ?
> >
>
> Gasp. This patch would contradict what's going on into
> do_sigwake_event(); well, if you are right, we would have entered the
> twilight zone with full ignition of the auxiliary boosters.
>
> Btw, XNRELAX is a state bit, not an information one. i.e.
>
> - if (xnthread_test_info(thread, XNKICKED)) {
> + if (xnthread_test_info(thread, XNKICKED) &&
> !xnthread_test_state(thread, XNRELAX)) {
The code in do_sigwake_event() prevents a relaxed thread from being
kicked, but not the other way around. Who knows in what order
things get done on an SMP system ?
--
Gilles Chanteperdrix.
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