linux-kernel - Re: [PATCH 09/10] n_tracerouter ldisc driver.

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Date:	Thu, 24 Feb 2011 21:27:28 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	J Freyensee <james_p_freyensee@...ux.intel.com>
cc:	gregkh@...e.de, linux-kernel@...r.kernel.org,
	suhail.ahmed@...el.com, christophe.guerard@...el.com
Subject: Re: [PATCH 09/10] n_tracerouter ldisc driver.

On Thu, 24 Feb 2011, J Freyensee wrote:
> > > +
> > > +	mutex_lock(&routelock);
> > > +	if (tr_data->opencalled == 0) {
> > > +
> > > +		tr_data->kref_tty = tty_kref_get(tty);
> > > +		if (tr_data->kref_tty == NULL)
> > > +			retval = -EFAULT;
> > > +		else {
> > 
> > Please use braces for the if as well. It's just irritating not to have
> > them before the else.
> 
> checkpatch.pl did not care about the lack of braces so that is why this
> got missed; I can add it.

It's not a strict requirement, but add it and look at the result. Then
judge yourself.

> > +static void n_tracerouter_close(struct tty_struct *tty)
> > > +{
> > > +	struct tracerouter_data *tptr = tty->disc_data;
> > > +
> > > +	WARN_ON(tptr->kref_tty != tr_data->kref_tty);
> > > +	tty_driver_flush_buffer(tty);
> > 
> > That code probably never run with lockdep as you would get a potential
> > deadlock warning. See n_tracerouter_open().
> > 
> > Though the deadlock cannot happen as you are protected by
> > tr_data->opencalled it does not make it more correct.
> > 
> 
> What do you suggest to make it correct for upstream?

Keep the lock ordering consistent. Either call that under the lock
always or do not.

Thanks,

	tglx
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