Re: Problem with SCHED_RR and kernel 2.4.18-4GB

[Roger Larsson]

> I'm a newbie at Linux, but have been busy developing (with some other
> people) sort of a DVB zapper demo application/stack on top of Hauppauge HW
> and SUSE 8.0 kernel 2.4.18-4GB for the last 2 months.  
 
> As the stack wil eventually be ported to one (or more) dedicated HW
> platforms, we defined an OS independant API. Now, we want to be able to set
> priorities, and have sort of a realtime behaviour.  
 
> The problem is that if I implement this, and set scheduling to be SCHED_RR,
> or SCHED_FIFO, my linux machine hangs. With SCHED_OTHER, I don't have that
> (note that for testing I used to set all prios to minimum (=1)).  

The big difference is that if a tread running as SCHED_RR or SCHED_FIFO never 
sleeps normal treads (like X, sh, login, ...) will not be given ANY CPU time 
- computer will appear hanged.

[BTW you are not running the same code in both cases due to ifdefs...]

But it is possible to get out of this situation if you prepared for it 
before... Use a higher priority monitor to detect looping RT processes and 
reduce their priorities!

(I have code if you are interested, please CC me as I am not subscibed to 
linux-kernel)


/RogerL

 
-- 
Roger Larsson
Skellefteå
Sweden
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