linux-kernel - Re: [PATCH 1/3] random: replace custom notifier chain with standard one

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Message-ID: <Yh+E3pnWM5lX+X0l@owl.dominikbrodowski.net>
Date:   Wed, 2 Mar 2022 15:53:18 +0100
From:   Dominik Brodowski <linux@...inikbrodowski.net>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        Netdev <netdev@...r.kernel.org>,
        Alexander Graf <graf@...zon.com>, Jann Horn <jannh@...gle.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Theodore Ts'o <tytso@....edu>
Subject: Re: [PATCH 1/3] random: replace custom notifier chain with standard
 one

Hi Jason,

Am Wed, Mar 02, 2022 at 12:42:56PM +0100 schrieb Jason A. Donenfeld:
> On Wed, Mar 2, 2022 at 6:35 AM Dominik Brodowski
> <linux@...inikbrodowski.net> wrote:
> >
> > Am Wed, Mar 02, 2022 at 12:10:36AM +0100 schrieb Jason A. Donenfeld:
> > >  /*
> > >   * Delete a previously registered readiness callback function.
> > >   */
> > > -void del_random_ready_callback(struct random_ready_callback *rdy)
> > > +int unregister_random_ready_notifier(struct notifier_block *nb)
> > >  {
> > >       unsigned long flags;
> > > -     struct module *owner = NULL;
> > > -
> > > -     spin_lock_irqsave(&random_ready_list_lock, flags);
> > > -     if (!list_empty(&rdy->list)) {
> > > -             list_del_init(&rdy->list);
> > > -             owner = rdy->owner;
> > > -     }
> > > -     spin_unlock_irqrestore(&random_ready_list_lock, flags);
> > > +     int ret;
> > >
> > > -     module_put(owner);
> > > +     spin_lock_irqsave(&random_ready_chain_lock, flags);
> > > +     ret = raw_notifier_chain_unregister(&random_ready_chain, nb);
> > > +     spin_unlock_irqrestore(&random_ready_chain_lock, flags);
> > > +     return ret;
> > >  }
> > > -EXPORT_SYMBOL(del_random_ready_callback);
> >
> > That doesn't seem to be used anywhere, so I'd suggest removing this function
> > altogether.
> 
> I thought about this, but it feels weird to have a registration
> function without an unregistration function... No other notifier is
> unbalanced like that.

... but having unused code compiled in (unless LTO is enabled, of course)
seems worse. Maybe comment it out, #ifdef COMPILE_TEST or something like
that?

Thanks,
	Dominik