linux-kernel - Re: [patch 1/3] tty: resolve tty contention between kernel and user space

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Message-ID: <20170709190814.GA913@sanghar>
Date:   Sun, 9 Jul 2017 20:08:14 +0100
From:   Okash Khawaja <okash.khawaja@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        Samuel Thibault <samuel.thibault@...-lyon.org>,
        Alan Cox <gnomes@...rguk.ukuu.org.uk>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        William Hubbs <w.d.hubbs@...il.com>,
        Chris Brannon <chris@...-brannons.com>,
        Kirk Reiser <kirk@...sers.ca>, speakup@...ux-speakup.org,
        devel@...verdev.osuosl.org
Subject: Re: [patch 1/3] tty: resolve tty contention between kernel and user
 space

Hi,

On Sun, Jul 09, 2017 at 06:04:17PM +0300, Andy Shevchenko wrote:
 
> Above
> 1. take mutex
> 2. take reference
> 
> Here:
> 1. give mutex back
> 2. give reference back
> 
> I think we usually see symmetrical  calls, i.e.
> 
> 1. give reference back
> 2. give mutex back
> 
> So, what did I miss?

After we hold the kref, driver won't disappear from underneath us so we
don't need tty_mutex just for decrementing the refcount.

Thanks,
Okash