Re: file offset pointer accross fork() ?

[Sebastian Skar <sebastianskar@xxxxxxxxx>]

On 9/30/05, Mulyadi Santosa <mulyadi.santosa@xxxxxxxxx> wrote:
> Hello....
>
> > hmm...
> > what's the user-perspective difference between forking and threading,
> > regarding open files, then ?
>
> IIRC nothing. The reason is, both normal fork() and thread creation,
> which essentially calls clone(), use CLONE_FS that duplicate pointer of
> file_struct. So, unless you directly call clone() without CLONE_FS, you
> will get same result regarding open files structures

I can't really agree with you.
lemme quote:

asmlinkage int sys_fork(struct pt_regs regs)
{
         return do_fork(SIGCHLD, regs.esp, &regs, 0, NULL, NULL);
}

fork uses SIGCHLD. only.

threads use CLONE_FS (which has nothing to do with open files.
it is the file system struct which is current working directory, etc)
and CLONE_FILES (which is open files).

so does fork really share the same file offset ?
what's the difference between forking and threading regarding open files ?

Thanks !!

>
> Hope it helps
>
> regards
>
> Mulyadi
>
>

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