pthreads and waitpid

(got a problem when sending this email, sorry for the inconvenience if you
get it multiple times)

> What kernel version and glibc version are you using?
>
> So you have a very simple program demonstrating the problem that you
> could post?

I use:
Linux debian 2.4.27-2-686 #1 Mon May 16 17:03:22 JST 2005 i686 GNU/Linux
libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x405c9000) (4.0.2-2)
libc.so.6 => /lib/libc.so.6 (0x40703000) (2.3.5.

I do not have a small program to demonstrate unfortunately, I could manage
to make the stuff work:
the waitpid function works only if the child process was forked directly.

I found in the man page of waitpid some blurbs about __WCLONE / __WALL I
think that I just understood what to do of that:
I should call something like: waitpid(pid, &status, WNOHANG|__WALL), isn't
it?
I imagine however that this __WALL is not portable to other Unices... do you
have an idea of which #ifdef I should use to protect the use of such macros?

I just tried with __WALL but got no luck, is there something special to do
to use that? the call always returns -1 even though the child exists.

Regards
Armel

On Wed, 17 May 2006 13:59:27 +0200, "Armel Asselin"
wrote:

>> What kernel version and glibc version are you using?
>>
>> So you have a very simple program demonstrating the problem that you
>> could post?
>
>I use:
>Linux debian 2.4.27-2-686 #1 Mon May 16 17:03:22 JST 2005 i686 GNU/Linux
>libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x405c9000) (4.0.2-2)
>libc.so.6 => /lib/libc.so.6 (0x40703000) (2.3.5.

Okay -- since you are on a 2.4.x kerenel, then you will be using
LinuxThreads. Under this implementation, only the creating thread can
wait for a child created using fork() (this does not conform to
POSIX...).

The modern threading implementation, NPTL, fixes this probem. But
you'll need a 2.6 kernel.

>I do not have a small program to demonstrate unfortunately, I could manage
>to make the stuff work:
>the waitpid function works only if the child process was forked directly.
>
>I found in the man page of waitpid some blurbs about __WCLONE / __WALL I
>think that I just understood what to do of that:
>I should call something like: waitpid(pid, &status, WNOHANG|__WALL), isn't
>it?
>I imagine however that this __WALL is not portable to other Unices... do you
>have an idea of which #ifdef I should use to protect the use of such macros?
>
>I just tried with __WALL but got no luck, is there something special to do
>to use that? the call always returns -1 even though the child exists.

Sorry -- bottom line is that you need Linux 2.6.

Cheers,

Michael