Re: RT linux

[John Sinclair <sinclairjw@ornl.gov>]

Emanuel,

One could imagine many systems with requirements which the use of a 
real-time kernel could satisfy.
For example, suppose you needed to talk to some synchronous serial device
that required the generation of output signals at precise intervals of 
precise duration and so forth.
If the device could tolerate +/- 50 us in the duration of this signal, 
then you would need to
be sure you could change its state with the same time precision. You 
could do this easily
with an FPGA or some other dedicated piece of hardware, but +/- 50 us is 
also in the range of a
software solution running under VxWorks or RTEMS or even some RTlinux. 
Running the software
on a non-realtime kernel would probably work most of the time but not 
all of the time. Doing the
same using posix realtime scheduling would be better, but it would still 
be possible for a piece of driver
code to cause problems so a realtime kernel (preemptive kernel using 
realtime scheduling alone) would
be the only reliable software solution (assuming we are excluding a 
hard-realtime solution).

John Sinclair

Emmanuel Mayssat wrote:
> Hello,
>
> I was wondering what would justify moving to RT linux?
> I was actually contemplating doing the move to RT myself, but finally
> decided against it.
>
> All RT-required feedback/acquisition/etc are implemented in
> hardware/electronics. As a result, my IOCs don't have to react
> Real-Time.
>
> But could you describe a "real" situation where RT is necessary? 
> Maybe if you have an IOC which is connected to a device that generate
> hardware interrupts, etc. but so far I never encountered such a device.
>
> Thanks,
>
> --
> E
>
> On Mon, 2007-09-10 at 05:59 -0500, David Kline wrote:
>   
> > you can use >=2.6.18 linux kernel/w patch from osadl 
> > (http://www.osadl.org/). that will give you rt behavior.
> > /david
> >
> > Heinrich du Toit wrote:
> >     
> > > Hi
> > >
> > > Did somebody else out there use RTLinux for EPICS?
> > >
> > > -Heinrich
> > >
> > >   
> > >       
> >     
>
>
>