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Date: Mon, 10 Jul 2017 09:31:05 +0100
From: Okash Khawaja <okash.khawaja@gmail.com>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Slaby <jslaby@suse.com>,
        Samuel Thibault <samuel.thibault@ens-lyon.org>,
        Alan Cox <gnomes@lxorguk.ukuu.org.uk>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        William Hubbs <w.d.hubbs@gmail.com>,
        Chris Brannon <chris@the-brannons.com>, Kirk Reiser <kirk@reisers.ca>,
        speakup@linux-speakup.org, devel@driverdev.osuosl.org
Subject: Re: [patch 1/3] tty: resolve tty contention between kernel and user
 space
Message-ID: <20170710083105.GA719@sanghar>
References: <20170708083803.GA23080@kroah.com>
 <20170709114153.157783481@gmail.com>
 <20170709114426.618570903@gmail.com>
 <CAHp75VdwWNj8PHRAMLqcQKhtT=sS5-n9T3n8GY1Rte=MKOQV-w@mail.gmail.com>
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On Sun, Jul 09, 2017 at 06:04:17PM +0300, Andy Shevchenko wrote:
> On Sun, Jul 9, 2017 at 2:41 PM, Okash Khawaja <okash.khawaja@gmail.com> wrote:
> 
> > +struct tty_struct *tty_kopen(dev_t device)
> > +{
> > +       struct tty_struct *tty;
> > +       struct tty_driver *driver = NULL;
> > +       int index = -1;
> > +
> > +       mutex_lock(&tty_mutex);
> > +       driver = tty_lookup_driver(device, NULL, &index);
> > +       if (IS_ERR(driver)) {
> 
> > +               mutex_unlock(&tty_mutex);
> > +               return ERR_CAST(driver);
> 
> Hmm... perhaps
> 
> tty = ERR_CAST(driver);
> goto out_unlock;
> 
> See below for further details.
> 
Sorry missed this one out. Since tty_lookup_driver has failed, we don't
need to down the refcount on driver. So we can return here, without
going to out_unlock.

Thanks,
Okash