Re: [Xenomai-help] no-brainer issue found, but not solved

[Jan Kiszka <jan.kiszka@domain.hid>]

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Steven Seeger wrote:
> I have found what seems to cause my problem.
> 
> I have two threads, t1 and t2.
> 
> t1 has a priority level of 30, and t2 has a priority level of 5. I am using
> the native skin, so t1 has the higher priority.
> 
> t2 is flashing an LED on my board every 40 ms, and t1 does nothing until I
> hit a key on the keyboard. When t1 activates, it does for(i=0; i<100000000;
> i++) which locks up my board for about 3 seconds. During this time, I expect
> my LED to stop flashing. However, the LED will flash a few times just once,
> at a rate of about 1 second. (Coincidentally, 1 second is the timing of
> another unrelated thread in the system.)
> 
> At the start of my t1 thread, I use syslog (a system call) to log that the
> thread is created. This call is made once before the thread goes into its
> loop, waiting for a global variable to be set otherwise just calling
> rt_task_wait_period(). If I comment out my call to syslog, which again I
> state is NOT in the thread loop, this behavior goes away. It seems that once
> a syscall is made in a shadow thread, xenomai fails to have it behave in a
> true hard realtime fashion. It's as if the thread stays relaxed.

It does stay relaxed until the next blocking RT function is invoked.
When unsure if this happens (I am from your description, maybe you
should rather post a code snippet), try rt_task_set_mode(0, T_PRIMARY,
NULL) before entering the loop.

> 
> Does this shed any light on the issue I have?
> 
> Steven
> 
> 

Jan


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