On Fri, 18 Mar 2005 Gopu Bhaskar wrote :
>
> >
> > dear sir
> > The number of processes that are being created in fork.c() in
> > function do_fork are less than the number of processes are being
> > terminated in exit.c in function do_exit().
> > I am placing a printk() in both the above functions do_fork()
> > and do_exit() and thus after compiling and then restarting i am
> > getting exit messages of many process ids that have not yet been
> > formed.
> >
>
>Perhaps pasting the code changes here (with context) may fetch more
>help.
>
> >
> > Another question is that while we are using an AND operation
> > to distinguish between a process and a thread (
> > if(p->flags & CLONE_VM)
> > in fork.c in function do_fork() in linux kernel 2.6.8 ).
>
>
>I dont know whether it is right to distinguish between
>threads and processes. Anyways the following link has
>Linus's thoughts on this.
>http://evanjones.ca/software/threading-linus-msg.html
>
> >
> > But if i use the above check in do_exit() , will it be able to
> > distinguish between a thread and a process in the same manner as
> > do_fork().
> > If this is not the case , then plz tell where i am wrong and
> > rectify my mistake.
> >
> > One more problem is while p->active_mm is equal to NULL in
> > case of kernel threads and not NULL in case of user level threads ;
> > through this check we can identify kernel and user level threads in
> > fork.c but
> > in exit.c the same p->active_mm value is not NULL for kernel and
> > user level threads.
>
>For kernel threads p->mm is NULL.
>When schedule() is called, if the next preocess to be scheduled is a
>kernel thread then next->active_mm is made equal to prev->active_mm.
>The active_mm is made NULL again when the kernel thread (mm == NULL)
>is being scheduled out. I guess do_exit is called before the thread
>is scheduled out so active_mm will not be NULL.
>
>Gopu.
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