Re: SCHED_RR preempted by SCHED_OTHER

["Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>]

On Mon, Jul 27, 2009 at 01:57:31PM +0200, Denis Richard wrote:
> Hi all,
> We work on powerpc board with kernel 2.6.29.6-rt23.
> The kernel is configured with  "Complete Preemption (Real-Time)".
> Working on our software, we have a strange behavior.
> A real time thread (SCHED_RR) can be preempted by non real time one  
> (SCHED_OTHER).
>
> We wrote a little test program (at the end of  this mail).
> This program creates 2 threads, a SCHED_RR one which processes during  
> about 12s
> (long for a real time, but just for test), and a SCHED_OTHER one,  
> started after the first one,
> which just modifies a global variable. The second one should not run  
> during the execution of
> the first one. But it appends, the global variable is modified.
>
> > rr_other
> Create thread
> OTHER ran during RR
> The end
> >
>
> Is it normal, a non real time thread preempts a real time one ? (we  
> think, it is not)
> Or is there something wrong in the test program, the kernel  
> configuration, ... ?
Does

	# echo -1 > /proc/sys/kernel/sched_rt_runtime_us

help?

Best regards
Uwe

-- 
Pengutronix e.K.                              | Uwe Kleine-König            |
Industrial Linux Solutions                    | http://www.pengutronix.de/  |
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