Re: [RFC][PATCH] ->signal->tty locking

[Oleg Nesterov <oleg@tv-sign.ru>]

On 10/17, Alan Cox wrote:
>
> Ar Maw, 2006-10-17 am 16:33 +0400, ysgrifennodd Oleg Nesterov:
> > I sent a patch,
> > 	http://marc.theaimsgroup.com/?l=linux-kernel&m=114268787415193
> > 
> > but it was ignored. Probably I should re-send it.
> 
> Definitely - we still see reports of tty slab scribbles

This patch can't fix anything, sorry for the confusion.

Yes, the 'if (new_sigh) {}' code in sys_unshare() is broken, but it is
never executed, because unshare_sighand() never populates new_sighp.

Probably it is better to just remove this code.

> > > Right, use tty_mutex when using the tty, use ->sighand when changing
> > > signal->tty.
> > 
> > I think that things like do_task_stat()/do_acct_process() do not need
> > global tty_mutex, they can use ->siglock.
> 
> Please keep the tty_mutex as it will protect against other stuff later.
> Once tty is a bit saner then someone brave can refcount it properly and
> that'll make it much prettier.

Oh, but it is silly to take the global tty_mutex in do_task_stat().
Why do we need it if ->siglock protects ->signal->tty ? We are only
reading the tty_struct, tty->driver can't go away ...

Oleg.

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