Re: 2.6.x Fork Problem?

[Alan Cox <alan@lxorguk.ukuu.org.uk>]

On Iau, 2004-08-12 at 01:01, Torin Ford wrote:
> I've widdled the code down to just do this:
> 
> pid = fork();
> switch (pid)
> {
>    case -1:
>       blah; /* big trouble */
>       break;
>    case 0: /* Child */
>       exit(1);
>       break;
>    default: /* Parent */
>       pid2 = waitpid(pid, &status, 0);
>       if (pid2 == -1)
>       {
>          blah;  /* check out errno */
>       }
> }
> 
> and I get the same results, so I now the exec has nothing to do with it.

Well I see two oddities in the example. You call exit() not _exit() so
the child will duplicate various queued stdio of the parent. Doesn't
seem to be relevant however.

Secondly and I suspect of importance you don't do anything with SIGCLD
so you are inheriting a random status. If the child signal is being
ignored then it will be cleared automatically. In that situation your
code functionality depends solely upon which thread runs first.