[Xenomai-help] Re: A fairly small rtnet/Xenomai application that freezes the

[Jan Kiszka <jan.kiszka@domain.hid>]

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Gilles Chanteperdrix wrote:
> M. Koehrer wrote:
>> Hi Jan, hi everybody,
>>
>> I have stripped down my program that is crashing Xenomai even further.
>> (I have attached the complete source code).
>> No rtnet is required.
>> Now I have the following real time task:
>>
>> static void realtimetask(void *arg)
>> {
>>     system("ls -l");
> 
> If you want to use system (or any function calling fork, eg popen or
> vfork) with Xenomai, you have to make sure to fault all pages mapped
> with write permission after the fork before trying to use services in
> priimary mode, because fork write protects all pages with write
> permission and notably the threads stacks. A piece of code that faults
> all pages follows.

Let me check if I got this correctly: fork calls mark all pages
write-protected - also those of the father process, or only those of the
new child? That would mean we see unexpected page faults, right?
Anything more (probably not a lock-up)?

I think we should document this special property somewhere, e.g. in the
wiki, maybe also a demo program in the examples repos.

Jan


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