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

[Gianluca Anzolin]

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.

Does it look better?

Thanks,
Gianluca
diff --git a/net/bluetooth/rfcomm/tty.c b/net/bluetooth/rfcomm/tty.c
index 84fcf9f..f455a22 100644
--- a/net/bluetooth/rfcomm/tty.c
+++ b/net/bluetooth/rfcomm/tty.c
@@ -437,9 +437,6 @@ static int rfcomm_release_dev(void __user *arg)
 		tty_kref_put(tty);
 	}
 
-	if (!test_and_set_bit(RFCOMM_TTY_RELEASED, &dev->flags))
-		tty_port_put(&dev->port);
-
 	tty_port_put(&dev->port);
 	return 0;
 }
@@ -673,6 +670,14 @@ static int rfcomm_tty_install(struct tty_driver *driver, struct tty_struct *tty)
 	if (err)
 		rfcomm_tty_cleanup(tty);
 
+	/* take over the tty_port reference if it was created with the
+	 * flag RFCOMM_RELEASE_ONHUP. This will force the release of the port
+	 * when the last process closes the tty. This behaviour is expected by
+	 * userspace.
+	 */
+	if (test_bit(RFCOMM_RELEASE_ONHUP, &dev->flags))
+		tty_port_put(&dev->port);
+
 	return err;
 }
 
@@ -1010,10 +1015,6 @@ static void rfcomm_tty_hangup(struct tty_struct *tty)
 	BT_DBG("tty %p dev %p", tty, dev);
 
 	tty_port_hangup(&dev->port);
-
-	if (test_bit(RFCOMM_RELEASE_ONHUP, &dev->flags) &&
-	    !test_and_set_bit(RFCOMM_TTY_RELEASED, &dev->flags))
-		tty_port_put(&dev->port);
 }
 
 static int rfcomm_tty_tiocmget(struct tty_struct *tty)