Re: [Xenomai-help] General question on Native Skin tasks

[Philippe Gerum <rpm@xenomai.org>]

Jan Kiszka wrote:
> Brian L. wrote:
> 
>>If I create a native-skin RT_TASK from userspace with no flags, i.e.
>>
>>void task(void*)
>>{
>>    for (;;) ;
>>}
>>int main()
>>{
>>   RT_TASK t;
>>   rt_task_create(&t, 0, 3, 0);
>>   rt_task_start(&t,task,0);
>>   (do something which blocks)
>>}
> 
> 
> mlockall left out for simplicity? Or is it also missing on your real
> test? In the latter case, occasional application crashes are "normal"
> (as described below).
> 
> Philippe, you suggested some code for detecting this. We should really,
> really add this soon (maybe to the exception path)!
> 

The submitted patch works pretty well detecting unlocked memory, I'm 
using it right now, but I'd like something a bit more self-explanatory 
than just receiving SIGXCPU. I don't think the execption path is the 
right place to put this, since the mlockall issue causes random bugs, 
and you likely want to detect them early and unconditionally.

> 
>>Should that task starve all other tasks? In what ways is it different
>>behaviorally from an ordinary posix thread? I ask because I have a
>>thread that might be spinning and a frozen system (back in the rtlinux
>>days, spinning in the real-time domain was a surefire way to freeze
>>without any other sign of trouble). If it is the case that this task
>>outweighs an ordinary linux thread/task, how can I make it the same?
> 
> 
> A task that has high priority than other system tasks has to outweigh
> them. This has nothing to to with POSIX (standard Linux included!),
> RTLinux, Xenomai, or whatever. But Xenomai has a simple watchdog to
> recover from run-away RT threads.
> 
> 
>>Also,  I haven't completely tracked this down yet, but xenomai seems
>>to be page-faulting in a loop and exploding rather spectacularly in a
>>native-skin multithreaded program that doesn't do anything outside of
>>relatively ordinary queue/mutex/task stuff. I'm upgrading to trunk to
>>see if it goes away.
>>
>>Short of a serial cable, is there a way to capture Oops/Panic text as
>>it flies by?
> 
> 
> linux/Documentation/networking/netconsole.txt is another option.
> 
> Jan
> 


-- 

Philippe.