linux-kernel - Re: [REGRESSION] rfcomm (userland) broken by commit 29cd718b

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Message-ID: <20131216211542.GA20419@sottospazio.it>
Date:	Mon, 16 Dec 2013 22:15:42 +0100
From:	Gianluca Anzolin <gianluca@...tospazio.it>
To:	Peter Hurley <peter@...leysoftware.com>
Cc:	Alexander Holler <holler@...oftware.de>, marcel@...tmann.org,
	Gustavo Padovan <gustavo@...ovan.org>,
	linux-bluetooth@...r.kernel.org, gregkh@...uxfoundation.org,
	jslaby@...e.cz, linux-kernel@...r.kernel.org
Subject: Re: [REGRESSION] rfcomm (userland) broken by commit 29cd718b

On Mon, Dec 16, 2013 at 09:58:58PM +0100, Gianluca Anzolin wrote:
> On Mon, Dec 16, 2013 at 09:27:20PM +0100, Gianluca Anzolin wrote:
> > On Mon, Dec 16, 2013 at 09:20:44PM +0100, Gianluca Anzolin wrote:
> > > On Mon, Dec 16, 2013 at 02:34:12PM -0500, Peter Hurley wrote:
> > > > 
> > > > This solution is acceptable to me, but I think the comment should briefly
> > > > explain why this fix is necessary, and the changelog should explain why in detail.
> > > > 
> > > > Perhaps with a fixme comment that rfcomm_tty_install() should just take over
> > > > the port reference (instead of adding one) and rfcomm_tty_cleanup() should
> > > > conditionally release on RFCOMM_RELEASE_ONHUP.
> > > > 
> > > > Because then:
> > > > 1) this fix would not be necessary.
> > > > 2) the release in rfcomm_tty_hangup() would not be necessary
> > > > 3) the second release in rfcomm_release_dev would not be necessary
> > > > 4) the RFCOMM_TTY_RELEASED bit could be removed
> > > > 
> > > > 
> > > > Regards,
> > > > Peter Hurley
> > > 
> > > Taking over the refcount in the install method would certainly look better. I'm
> > > going to test it ASAP :D
> > > 
> > > But why getting rid of the release in in rfcomm_tty_hangup()?
> > > We could lose the bluetooth connection at any time and the dlc callback
> > > would have to hangup the tty (and release the port if necessary).
> > > 
> > > Also the RFCOMM_TTY_RELEASED bit should still be necessary if the port is
> > > created without the RFCOMM_RELEASE_ONHUP flag.
> > > 
> > > Besides any process could release the port behind us (with the command rfcomm
> > > release rfcomm1 for example).
> > > 
> > > Gianluca
> > 
> > Nevermind I figured it out the reason...
> 
> I'm testing the attached patch ATM, which does what you described. It works
> very well.
> 
> It doesn't remove the RFCOMM_TTY_RELEASE flag yet, another patch should remove
> that bit.

ok, replying to myself again (sorry for that). RFCOMM_TTY_RELEASE cannot go
away. We have still to manage the case where the port is opened without
RFCOMM_RELEASE_ONHUP.

This last patch does release the port in that situation.

Tested with:
# rfcomm bind 1 <addr>
# rfcomm release 1

and with
# rfcomm connect 1 <addr>

Thanks,
Gianluca

View attachment "rfc3.patch" of type "text/x-diff" (1320 bytes)