linux-kernel - Re: [Bluez-devel] Oops involving RFCOMM and sysfs

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Message-ID: <20080117081504.GA3123@darkstar.te-china.tietoenator.com>
Date:	Thu, 17 Jan 2008 16:15:04 +0800
From:	Dave Young <hidave.darkstar@...il.com>
To:	Gabor Gombas <gombasg@...aki.hu>
Cc:	Cornelia Huck <cornelia.huck@...ibm.com>,
	Tejun Heo <htejun@...il.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	linux-kernel@...r.kernel.org, bluez-devel@...ts.sf.net,
	kay.sievers@...y.org, Greg KH <greg@...ah.com>,
	Marcel Holtmann <marcel@...tmann.org>, davem@...emloft.net
Subject: Re: [Bluez-devel] Oops involving RFCOMM and sysfs

On Thu, Jan 17, 2008 at 03:24:50PM +0800, Dave Young wrote:
> On Jan 17, 2008 7:06 AM, Gabor Gombas <gombasg@...aki.hu> wrote:
> > Hi,
> >
> > On Wed, Jan 16, 2008 at 09:02:05AM +0800, Dave Young wrote:
> >
> > > The rfcomm tty device will possibly retain even when conn is down,
> > > and sysfs doesn't support zombie device moving, so this patch
> > > move the tty device before conn device is destroyed.
> > >
> > > Signed-off-by: Dave Young <hidave.darkstar@...il.com>
> >
> > This seems to work, both the oops and the hang are gone. I get these
> > messages in syslog when the Bluetooth link hangs and I want to kill pppd
> > with "poff":
> >
> > Jan 16 23:55:59 twister kernel: unregister_netdevice: waiting for ppp0 to become free. Usage count = 1
> > Jan 16 23:56:09 twister kernel: unregister_netdevice: waiting for ppp0 to become free. Usage count = 1
> >
> > But a "killall -9 pppd" seems to help and then the re-connect (after the
> > phone got power-cycled) works.
> 
> Weird, I guess "device_move(dev, NULL) two times" cause the problem.
> 
> Anyway, device_move should check the old_parent and new_parent , if
> they equal to each other then just return.
> 
> Am I right?

Could you apply this patch as well to test? Thanks.

diff -upr linux/net/bluetooth/rfcomm/tty.c linux.new/net/bluetooth/rfcomm/tty.c
--- linux/net/bluetooth/rfcomm/tty.c	2008-01-17 16:09:34.000000000 +0800
+++ linux.new/net/bluetooth/rfcomm/tty.c	2008-01-17 16:10:22.000000000 +0800
@@ -692,7 +692,8 @@ static void rfcomm_tty_close(struct tty_
 	BT_DBG("tty %p dev %p dlc %p opened %d", tty, dev, dev->dlc, dev->opened);
 
 	if (--dev->opened == 0) {
-		device_move(dev->tty_dev, NULL);
+		if (dev->tty_dev->parent)
+			device_move(dev->tty_dev, NULL);
 
 		/* Close DLC and dettach TTY */
 		rfcomm_dlc_close(dev->dlc, 0);

> 
> >
> >
> > Gabor
> >
> > --
> >      ---------------------------------------------------------
> >      MTA SZTAKI Computer and Automation Research Institute
> >                 Hungarian Academy of Sciences
> >      ---------------------------------------------------------
> >
--
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