Re: [Xenomai] Re : Sporadic problem : rt_task_sleep locked after debugging

[Paolo Minazzi <Paolo.Minazzi@mitrol.it>]

I think to be very near to the solution of this problem.
Thanks to Gilles for his patience.

Now I will retry to make a summary of the problem.

********************
**** MY PROBLEM ****
********************
I have an user space xenomai application.
It works fine. If I try to debug it with gdb, sometimes, in some points,
xenomai stops to works. All xenomai threads are like stopped.
In my case they are stopped in rt_task_sleep() or other wait operations.
Linux instead continues to work normally.
To make xenomai usable and working I have to reset the processor.
I have no other way.


**************************
**** SOLUTION / PATCH ****
**************************
file          :   xenomai-2.5.6/ksrc/skins/native/task.c
function      :   int rt_task_delete(RT_TASK *task)

See my code signed with =======>

int rt_task_delete(RT_TASK *task)
{
         int err = 0;
         spl_t s;

         if (!task) {
                 if (!xnpod_primary_p())
                         return -EPERM;

                 task = xeno_current_task();
         } else if (xnpod_asynch_p())
                 return -EPERM;

         xnlock_get_irqsave(&nklock, s);

         task = xeno_h2obj_validate(task, XENO_TASK_MAGIC, RT_TASK);

         if (!task) {
                 err = xeno_handle_error(task, XENO_TASK_MAGIC, RT_TASK);
                 goto unlock_and_exit;
         }

         /* Make sure the target task is out of any safe section. */
         err = __native_task_safewait(task);

         if (err)
                 goto unlock_and_exit;

         =========> if (xnthread_test_state(&task->thread_base, XNDEBUG))
         =========> {
         =========>     unlock_timers();
         =========> }


         /* Does not return if task is current. */
         xnpod_delete_thread(&task->thread_base);

       unlock_and_exit:

         xnlock_put_irqrestore(&nklock, s);

         return err;
}

As you can see, my patch unlock timers if the xenomai thread is killed.


***************************
**** DETAILS OF MY BUG ****
***************************
I have a xenomai application with 70 real-time threads.
Suppose that thread 1 deletes thread 70 with rt_task_delete().
This is my case.

I put a breakpoint and run my xenomai application.
When my breakpoint is reached gdb stops all my xenomai threads.

If I press "c" to continue, gdb restarts my application,
that is every thread, one by one (thread 1, thread 2, thread 3,
.... , thread 70).

If I press "c" on gdb, the following scenario could happens :

1) gdb start thread 1
2) thread 1 starts immediately
3)   thread 1 delete thread 70 by rt_task_delete()
...
4) gdb start thread 2
5) gdb start thread 3
6) gdb start thread 4
7) gdb start thread 5
8) gdb start thread 6
...
.) gdb start thread 68
.) gdb start thread 69
.) gdb start thread 70

The thread 1 finds thread 70 in debug mode !

My patch adjust this problem.

I realize that it is a very special case, but it is my case.

I'd like to know if the patch is valid or can be written in a different way.
For example, I could insert my patch directly in xnpod_delete_thread().

The function unlock_timers() cannot be called from 
xenomai-2.5.6/ksrc/skins/native/task.c
because it is defined static. This is a detail. There are simple ways to 
solve this.

Thanks in advance,
Paolo Minazzi