[okl4-developer] Direct IPC from OKLinux userland processes to OKL4 services

[Jorge Torres]

Hi,

This is in order to correct my last e-mail, since now that I read; it isn't
a bit clear:

I think that dealing with OKLinux scheduler invariants is possible, if we
avoid a thread performing L4 native calls being scheduled by OKLinux, this
could happen if we send such thread to a waitqueue, and set its priority to
be higher than the main and timer (oklinux) threads, once the thread is done
performing as l4 native, it should be taken out of the waitqueue, and its
priority should be set to the one it had initialy.

That will be pretty much, what I meant on the last e-mail,

Cheers,

Jorge

On Thu, Feb 28, 2008 at 2:11 AM, Nelson Tam <nelson at ok-labs.com> wrote:

> Hi Damien,
>
> On 26/02/2008, at 01:27, Damien Schulz wrote:
>
> > is it possible to have IPC directly from OKLinux userland processes
> > - no matter if it is a good idea or not? So far I've written a
> > procfs module that is able to communicate with OKL4, but I'd like to
> > directly use the IDL interface in my user processes.
> >
> > If I understand it correctly, every linux process is started as an
> > OKL4 process, so it should be possible anyway. Is there a way to
> > simply allow IPC or would that require further changes in the
> > OKLinux fork() implementation?
>
> I'm sorry about the confusion earlier.  Let me clarify a few things.
>
> What I said in the previous email about OKLinux threads being able to
> use OKL4 services holds true for OKLinux _kernel_ threads only.  There
> are 2 threads in this category - called "timer_thread" and
> "main_thread".  You can find them in kernel-2.6.10-v1/arch/l4/kernel -
> take a look in sys_iguana.c and main.c.  These 2 threads have their
> own L4 space.
>
> On the other hand, OKLinux _user_ threads runs your Linux userland
> processes in a different L4 space from the kernel threads.  The
> important thing here is that, L4 implements IPC security mechanisms on
> a per-L4-address-space basis.  While the OKLinux kernel space is given
> permission to IPC any thread in other spaces, the OKLinux user space
> is not allowed to do so.  Therefore, your OKLinux user processes won't
> be able to communicate with OKL4 services.
>
> Now you might be asking why can't you just configure the IPC
> permissions so that the OKLinux user space can IPC everyone.  The
> short answer is that, the OKLinux kernel relies on some invariants on
> when and how OKLinux user threads get scheduled.  Once you allow
> OKLinux user threads to IPC freely, these invariants get violated.
>
> I hope this answers your question.
>
> Nelson.
>
>
> _______________________________________________
> Developer mailing list
> Developer at okl4.org
> https://lists.okl4.org/mailman/listinfo/developer
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.okl4.org/pipermail/developer/attachments/20080228/47f42850/attachment.htm