[Rtai] can't init usermode tasks

[Chris Cole]

Hey all,
I've just installed the linux-image-2.6.24-16-rtai package which is in
the linuxcnc archive and I had a couple (I think easy?) questions.

I go into /usr/realtime-2.6.24-16-rtai/testsuite/user/latency (as a
normal user), I type ./run and I get:

CANNOT INIT MASTER TASK

but when I run this as root I get successful output.

I also made a really simple c++ program to test this:
// file test.cc
#include <rtai_lxrt.h>
#include <iostream>
#include <cstdlib>
using namespace std;

int main()
{
  RT_TASK *foo = rt_task_init(nam2num("test"), 0, 0, 0);
  if (!foo)
    {
      cout << "can't init realtime task" << endl;
      exit(1);
    }
  return 0;
}


compiling and running this above example yields:

ccole at darter:~$ uname -r
2.6.24-16-rtai
ccole at darter:~$ g++ test.cc -I/usr/realtime-2.6.24-16-rtai/include -o test
ccole at darter:~$ ./test
can't init realtime task
ccole at darter:~$ sudo ./test
Segmentation fault

So, in short I'm confused -- why should I be able to run the latency
test as root, but then have something as simple as rt_init_task
segfault? Also, unless I'm mistaken, shouldn't I be able to run these
tasks as myself (not root)? I've tried this on two different hardware
platforms now with the same results. Maybe someone could provide me with
insight on where to start tracing things out when they fail?


Chris