[uml-devel] Re: [uml-user] UNIX socket networking

[Patrick Kilian <petschge@gmx.de>]

Hi all,

>> Problem 1.) How do I shutdown a kernel thread when the uml goes
>> down? At the moment my patched kernle gets stuck with 100% CPU
>> usage when I trie to shut down the uml kernel.
> Possibly can be done either through exitcall or uml_exitcall. Give a
> look at the arch/um/kernel/sigio_*.c, especially at sigio_cleanup,
> which is an UML exitcall. Note however that the thread it refers to
> exists only on the host; it could be your case or not.
I did some test with exitcall but it didn't work out. Looks like I was 
trying to do the roght thing, but did some mistakes.

>> Problem 2.) How can I make sure that my kernel thread I startet
>> _after_ the networking stuff is inited? At the moment I start the
>> kernel thread with a __initcall and just do a sleep(30) in the
>> thread.
> The proper way would be to use late_initcall instead of __initcall
> (check in <linux/init.h>), supposing that network does not already
> use late_initcall.
I didn't know about late_initcall, but it sounds promising.

> Or you can just hack the network initcall and make it call your
> function; or your initcall can call the network init.
I wanted to avoid hacking the network code itself.

> In this case, to avoid double initialization, add at the start of
> network_init (or how is it called) something like:
>
> if (network_already_inited)
>   return (Ok?);
> network_already_inited = 1;
>
> and before, in the same file:
> static int network_already_inited = 0;
>
> However rename the flag or someone could think you are a Pascal
> programmer (actually, I was). Seems like the actual function is
> called sock_init.
Well, I'll give it a try.


> Also, in 2.6 (what I am checking) initcalls are called after sock_init 
> (in init/main.c: do_basic_setup()). So if that is right you do not 
> need anything to make sure that your initcall is after network
> initialized.
The first time I ran into this problem was on 2.4.*. But I tried IIRC on 
2.6.* too and had the same problems.

>> Problem 3.) I can only create sockets in the "anonymous" namespace.
>> The normal namespace gives me some error which I don't rememeber
>> right now but I could find out what th errorcode was.
> Sorry, but I cannot find any "anonymous" namespace. What is it? Maybe
> PF_UNSPEC?
It's abstract namespace (sorry for my mistake):

It's also in PF_LOCAL but with names that start with \0. I was told to 
try this on the linux kernel newbies list. If you google with my name 
and socket you should be able to find that thread.

> I guess the "normal" namespace is PF_LOCAL.
IIRC yes.

>> So if somebody could help me with this problem I'd be willing to
>> put some more work into this. Or I could post my tried on this list
>> or by pm
> There has been a lot of request for a such feature, so I would like
> if you can post it here or rather on uml-devel (especially to avoid
> anyone trying it without specific knowledge), even if it is not
> complete. So we could better help you. Also, state whether it is onto
> 2.4 or 2.6.
It's just some basic test. Far from being a working patch. I'll try your 
sugestions and send in a patch in the next few days.

Thanks for your help,
Patrick "Petschge" Kilian



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