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From: Okash Khawaja <okash.khawaja@gmail.com>
To: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Jiri Slaby <jslaby@suse.com>,
	Samuel Thibault <samuel.thibault@ens-lyon.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 0/3] Re: tty contention resulting from tty_open_by_device export
Date: Mon, 10 Jul 2017 17:22:01 +0100	[thread overview]
Message-ID: <20170710162201.GB417@sanghar> (raw)
In-Reply-To: <20170710123307.GA777@sanghar>

On Mon, Jul 10, 2017 at 01:33:07PM +0100, Okash Khawaja wrote:
> > If the tty counts are being misreported then it would be better to fix
> > the code to actually manage the counts properly. The core tty code is
> > telling you that the tty is not in a valid state. While this is of
> > itself a good API to have, the underlying reference miscounting ought
> > IMHO to be fixed as well.
> When opening from kernel, we don't use file pointer. The count mismatch
> is between tty->count and #fd's. So opening from kernel leads to #fd's
> being less than tty->count. I thought this difference is relevant to
> user-space opening of tty, and not to kernel opening of tty. Can you
> suggest how to address this mismatch?
Idea is tty_kopen only ever returns a newly initialised tty - returned
by tty_init_dev. Since the access is exclusive, tty->count shouldn't
matter. When the caller is done with it, it calls tty_release_struct
which frees up the tty itself.

But yes, all the while a tty is kopened, its tty->count and #fds will be
unequal.

Thanks,
Okash

  reply	other threads:[~2017-07-10 16:22 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-07-07 20:28 tty contention resulting from tty_open_by_device export Okash Khawaja
2017-07-08  8:38 ` Greg Kroah-Hartman
2017-07-08  9:01   ` Okash Khawaja
2017-07-09 11:41   ` [patch 0/3] " Okash Khawaja
2017-07-09 11:41     ` [patch 1/3] tty: resolve tty contention between kernel and user space Okash Khawaja
2017-07-09 11:51       ` Greg Kroah-Hartman
2017-07-09 15:04       ` Andy Shevchenko
2017-07-09 19:08         ` Okash Khawaja
2017-07-10  8:31         ` Okash Khawaja
2017-07-10 15:21           ` Andy Shevchenko
2017-07-10 16:12             ` Okash Khawaja
2017-07-09 11:41     ` [patch 2/3] staging: speakup: use tty_kopen instead of tty_open_by_driver Okash Khawaja
2017-07-09 11:50       ` Greg Kroah-Hartman
2017-07-09 12:28         ` Okash Khawaja
2017-07-09 11:41     ` [patch 3/3] tty: undo export " Okash Khawaja
2017-07-09 11:57     ` [patch 0/3] Re: tty contention resulting from tty_open_by_device export Greg Kroah-Hartman
2017-07-09 12:32     ` [patch 4/3] tty: make tty_kopen return ENODEV in case of no TTY Okash Khawaja
2017-07-10 11:52     ` [patch 0/3] Re: tty contention resulting from tty_open_by_device export Alan Cox
2017-07-10 12:33       ` Okash Khawaja
2017-07-10 16:22         ` Okash Khawaja [this message]
2017-07-12 18:20         ` Alan Cox
2017-07-13 11:29           ` Okash Khawaja
2017-07-17 12:31             ` Greg Kroah-Hartman
2017-07-17 13:23               ` Okash Khawaja
2017-07-17 22:04                 ` Alan Cox
2017-07-18 11:29                   ` Okash Khawaja
2017-07-18 12:26                     ` Dan Carpenter
2017-07-18 19:22                       ` Okash Khawaja
2017-07-18 13:49                     ` Alan Cox
2017-07-20  7:22                       ` [patch v3 0/3] tty contention resulting from tty_open_by_driver export Okash Khawaja
2017-07-20  7:22                         ` [patch v3 1/3] tty: resolve tty contention between kernel and user space Okash Khawaja
2017-07-20  7:22                         ` [patch v3 2/3] staging: speakup: use tty_kopen and tty_kclose Okash Khawaja
2017-07-20  7:22                         ` [patch v3 3/3] tty: undo export of tty_open_by_driver Okash Khawaja
2017-07-17 21:04               ` [patch v2 0/3] tty contention resulting from tty_open_by_driver export Okash Khawaja
2017-07-17 21:04                 ` [patch v2 1/3] tty: resolve tty contention between kernel and user space Okash Khawaja
2017-07-17 21:04                 ` [patch v2 2/3] staging: speakup: use tty_kopen instead of tty_open_by_driver Okash Khawaja
2017-07-17 21:04                 ` [patch v2 3/3] tty: undo export " Okash Khawaja

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