[Xenomai-help] Re: A fairly small rtnet/Xenomai...

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

Dmitry Adamushko wrote:
> On 22/12/06, Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org> wrote:
> 
>>In absence of a better solution, I would recommend to use the "fault_vm"
>> function after each fork.
> 
> 
> But it's not safe. It doesn't stop any other rt threads (if there are
> a few in this app.) from touching the wp-pages (it's not only about
> stacks after all) in the mean time. So fault_vm() only increases the
> probability of not-crashing but doesn't eliminate it completely.
> 
> So all the contextes have to be blocked starting from the moment
> fork() is about to be called and till the moment a subsequent
> fault_vm() is done.
> It's ugly and that suggests fork() is not ok here at all.
> 
> And btw, vfork() should be a funny thing being called from
> multi-threaded app. It blocks a calling context and borrows its
> address space while other threads are continuing to run, well, with
> the same context (maybe it's handled somehow, have to check).

fault_vm is safe to use only if you are calling fork at a time when
there is only one thread. So, if your application is forking at init, it
should be OK.

-- 
                                                 Gilles Chanteperdrix