The way I like to think of is is as follows.
When RTLinux is running, RTLinux is a single POSIX process running on a bare
machine.
RTLinux is multithreaded with, normally, one thread being Linux.
The RT components of RTLinux applications are threads and signal handlers (interrupt
handlers) that run in this single process.
Before RTLinux starts, Linux is running as the OS. Insmoding the RTLinux modules
essentially pushes Linux out of its place as the system foundation and makes the
RT kernel take its place.
I'm attaching a picture, perhaps it will help.
On Tue, May 30, 2000 at 11:44:29PM +0100, Mark wrote:
> Hi,
>
> I'm just trying to figure out how to visualise what going on
> when RT-Linux is running. I'm a bit confused trying to figure out how an
> RT Linux system fits together.
>
> For me, with a normal Linux kernel, I think of is running a number of
> individual processes. When threads turn up in Linux (VMS or Windoze for
> that matter) I think of it as being a separate execution sequence (It
> own memory etc.) BUT it is with in a process. That is it can only get a
> chance to run when the process is switched into the CPU AND that thread
> within the particular process is chosen to execute.
>
> With RT-Linux is there only ONE process on the system. Is then has a
> number of threads inside it (One of which is the Linux Kernel). Then to
> start a RTL program off you have to insmod it into the single process?
>
> I would have a problem if RTL just ran normal processes, where the idle
> process was the Linux Kernel. Indeed this is what I though happened,
> judging by some of the documents. But the thread stuff seems to
> contradict this. Has it been updated in some way.
>
> Maybe there is a diagram around showing this. As yet I haven't seen on.
> On my webpage I've put, what I think is going on. If someone could take
> a look and tell me if I way off (Most likely:) of what ever. I'd really
> appreciate it.
>
> http://www.mxnet.demon.co.uk/RT-Linux/RTLinux.html
>
> Many Thanks
>
> Mark
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expandproces.jpg.gz
expandproces.jpg.gz