Re: [Xenomai-core] [BUG?] stalled xeno domain

[Philippe Gerum <rpm@xenomai.org>]

Jan Kiszka wrote:
> Philippe Gerum wrote:
> 
>>Jan Kiszka wrote:
>>
>>>Philippe Gerum wrote:
>>>
>>>
>>>>Jan Kiszka wrote:
>>>>
>>>>
>>>>>>>Philippe, do you see any remaining issues, e.g. that the leak
>>>>>>>survived
>>>>>>>the task termination? Does this have any meaning for correct
>>>>>>>driver and
>>>>>>>skin code?
>>>>>>>
>>>>>>
>>>>>>The only way I could see this leakage survive a switch transition
>>>>>>would
>>>>>>require it to happen over the root context, not over a primary
>>>>>>context.
>>>>>>Was it the case?
>>>>>>
>>>>>
>>>>>
>>>>>The task had to leave from primary mode. If I forced it to secondary
>>>>>before terminating, the problem did not show up.
>>>>>
>>>>
>>>>But does the code causing the leakage could have been run by different
>>>>contexts in sequence, including the root one?
>>>>
>>>
>>>
>>>I don't think so. Bugs in our software aside, there should be no switch
>>>to secondary mode until termination. Moreover, we installed a SIGXCPU
>>>handler, and that one didn't trigger as well.
>>>
>>>
>>>I just constructed a simple test by placing rthal_local_irq_disable() in
>>>rt_timer_spin and setting up this user space app:
>>>
>>>#include <stdio.h>
>>>#include <signal.h>
>>>#include <native/task.h>
>>>#include <native/timer.h>
>>>
>>>RT_TASK task;
>>>
>>>void func(void *arg)
>>>{
>>>    rt_timer_spin(0);
>>>}
>>>
>>>
>>>void terminate(int sig)
>>>{
>>>    printf("joining...\n");
>>>    rt_task_join(&task);
>>>    rt_task_delete(&task);
>>>    printf("done\n");
>>>}
>>>
>>>
>>>int main()
>>>{
>>>    signal(SIGINT, terminate);
>>>    rt_task_spawn(&task, "lockup", 0, 10, T_FPU | T_JOINABLE | T_WARNSW,
>>>                  func, NULL);
>>>    pause();
>>>    return 0;
>>>}
>>>
>>>
>>>Should this lock up (as it currently does) or rather continue to run
>>>normally after the RT-task terminated? BTW, I'm still not sure if we are
>>>hunting shadows (is IRQs off a legal state for user space in some skin?)
>>>or a real problem - i.e. is it worth the time.
>>>
>>
>>I've just tested this frag against the current SVN head, patching
>>rt_timer_spin() as required, and cannot reproduce the lockup. As
> 
> 
> Are you sure that you actually used the modified native skin for the test?
> 

Yep, checked twice.

> 
>>expected, the incoming root thread reinstates the correct stall bit
>>(i.e. clears it) after the RT thread terminates. Any chance some
>>potentially troublesome stuff exists in your setup?
>>
> 
> 
> I just re-verified this behaviour on a slightly different setup (still
> 2.6.15-ipipe-1.2-02, xeno trunk), and I'm going to try this on a third
> box with 2.6.16+tracing soon. So far I still have a stuck timer IRQ
> after the test.
> 
> Jan
> 


-- 

Philippe.