[EMSCB] L4Linux + IPC

Oskar Senft o.senft at sirrix.com
Wed May 3 17:21:34 CEST 2006

Hi Frank!

> `Alien' means that this task is special handled by the Fiasco kernel.
> In contrast to normal behaviour, L4 syscalls executed in the context
> of an alien task generate exceptions just before and after the
> L4 syscall. These exceptions allow the L4Linux server to set the
> internal Linux state of that task to "disk wait" to prevent that
> task from the Linux scheduling.
Ok, thank you for the explanation. Where could I read more about that?

>> The above sample always blocks for 
>> exactly the IPC wait time. Then it runs again (accepting input, eg. from
>> keyboard) and blocks again. It can be terminated by pressing CTRL-C as
>> the input seems to be queued until the IPC wait timeout expired.
> I cannot check this as I'm currently work with a different branch, but
> I would expect the exact behaviour as you describe. Or are _all_
> Linux applications frozen while this task waits for an incoming IPC?
Yes, that is the problem. As I already described, neither switching to
another Linux Console (ALT-F2, ...) nor SSH work when the process blocks
- so I guess that all other processes (besides of the test and SSHD) are
frozen, too. The freezing of the *single* process is a expected - sure.


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