Writing as init without /dev/console?

Writing as init without /dev/console?

[Nico Schottelius]

[-- Attachment #1: Type: text/plain, Size: 1613 bytes --]

Hello!

Currently I do not open /dev/console in cinit, but currently
I do see very strange behaviour:

If the first printf() in the following code (from serv/cinit.c) is
enabled, the socket communication will later fail:

----------------------------------------------------------------------
#ifdef DEBUG
//   printf("ARGC=%d\n",argc);
#endif

   set_signals(ACT_SERV);  /* set signal handlers */
#ifdef DEBUG
   printf("ARGC=%d\n",argc);
#endif
----------------------------------------------------------------------

I don't know what could be the relation between this printf and the
behaviour that cinit-0.1 later hangs in comm/do_result when reading
the resulting byte from a socket.

If you want to see the full code, it can be found at [0].

This code contains serv/cinit.c, which is the same as found
in cinit-0.0.8 [1] and serv/cinit.c-cinit0.1, which is the one
with a bit more debugging and the printf() before set_signals,
which makes cinit hang in comm/do_result at the position when
fpoint() is called.

Perhaps this is an issue with not opening /dev/console? It's just
a guess, because I don't have any idea what could cause this behaviour.

If someone has _any_ idea, I would be very thankful.

Nico

[0]: http://creme.schottelius.org/~nico/pre-release/cLinux/cinit-0.1-rc4.tar.bz2

P.S.: I do read replies to the mailing list via web-interface, replies
      to me must be confirmed otherwise.

-- 
Keep it simple & stupid, use what's available.
Please use pgp encryption: 8D0E 27A4 is my id.
http://nico.schotteli.us | http://linux.schottelius.org

[-- Attachment #2: Type: application/pgp-signature, Size: 827 bytes --]

Re: Writing as init without /dev/console?

[Miquel van Smoorenburg]

In article <20050620135132.GB2779@schottelius.org>,
Nico Schottelius  <nico-kernel@schottelius.org> wrote:
>Currently I do not open /dev/console in cinit, but currently
>I do see very strange behaviour:
>
>If the first printf() in the following code (from serv/cinit.c) is
>enabled, the socket communication will later fail:

printf() prints to stdout i.e. filedescriptor #1. If you do not
open stdin/stdout/stderr in your program, you do not know what
is going to be fd #1 later on .. in your case, the socket probably
is fd #1 and the printf() is happily printing to it.

To prevent this, do something like this at the start of your program:

	int n;

	do {
		n = open("/dev/null", O_RDWR);
	} while (n >= 0 && n <= 2);
	close(n);

Mike.