linux-kernel - Re: [Regression] Bluetooth RFComm: using it locks up the machine

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Date:	Sun, 04 Mar 2007 10:12:22 -0500
From:	Mark Lord <lkml@....ca>
To:	Mark Lord <lkml@....ca>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>,
	bluez-devel@...ts.sf.net, marcel@...tmann.org,
	Andrew Morton <akpm@...l.org>,
	"David S. Miller" <davem@...set.davemloft.net>
Subject: Re: [Regression] Bluetooth RFComm:  using it locks up the machine

Mark Lord wrote:
> Any attempt to open/use a bluetooth rfcomm device locks up
> scheduling completely on my machine.
> 
> Interrupts (ping, alt-sysrq) seem to be alive, but nothing else.
> 
> This was working fine in 2.6.20, broken now in 2.6.21-rc2-git*

Further info:  Reverting this change (below) fixes it:

| author	Marcel Holtmann <marcel@...tmann.org>
| 	 Sat, 17 Feb 2007 22:58:57 +0000 (23:58 +0100)
| committer	David S. Miller <davem@...set.davemloft.net>
| 	 Mon, 26 Feb 2007 19:42:41 +0000 (11:42 -0800)
| commit	c1a3313698895d8ad4760f98642007bf236af2e8
| tree	337a876f727061362b6a169f8759849c105b8f7a	tree | snapshot
| parent	f5ffd4620aba9e55656483ae1ef5c79ba81f5403	commit | diff
| 
| [Bluetooth] Make use of device_move() for RFCOMM TTY devices
| 
| In the case of bound RFCOMM TTY devices the parent is not available
| before its usage. So when opening a RFCOMM TTY device, move it to
| the corresponding ACL device as a child. When closing the device,
| move it back to the virtual device tree.
| Signed-off-by: Marcel Holtmann <marcel@...tmann.org>

Specifically, I reverted these changes, below, to fix it:

--- 2.6.20/net/bluetooth/rfcomm/tty.c	2007-02-04 13:44:54.000000000 -0500
+++ 2.6.21/net/bluetooth/rfcomm/tty.c	2007-03-02 15:06:32.000000000 -0500
@@ -74,6 +74,8 @@
 	wait_queue_head_t       wait;
 	struct tasklet_struct   wakeup_task;

+	struct device		*tty_dev;
+
 	atomic_t 		wmem_alloc;
 };

@@ -261,7 +263,7 @@
 		return err;
 	}

-	tty_register_device(rfcomm_tty_driver, dev->id, rfcomm_get_device(dev));
+	dev->tty_dev = tty_register_device(rfcomm_tty_driver, dev->id, NULL);

 	return dev->id;
 }
@@ -630,6 +632,9 @@
 	set_current_state(TASK_RUNNING);
 	remove_wait_queue(&dev->wait, &wait);

+	if (err == 0)
+		device_move(dev->tty_dev, rfcomm_get_device(dev));
+
 	return err;
 }

@@ -642,6 +647,8 @@
 	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);
+
 		/* Close DLC and dettach TTY */
 		rfcomm_dlc_close(dev->dlc, 0);

-
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