linux-kernel - Kernel bug: bluetooth meets TTY layer

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Message-ID: <476A895C.7040903@linux.intel.com>
Date:	Thu, 20 Dec 2007 16:25:16 +0100
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Marcel Holtmann <marcel@...tmann.org>
CC:	linux-kernel@...r.kernel.org
Subject: Kernel bug: bluetooth meets TTY layer

Hi,

with the help of kerneloops.org I've spotted a nice little interaction
between the TTY layer and the bluetooth code, however the tty layer is
not something I'm all too familiar with so I rather ask than brute-force
fix the code incorrectly.

The raw details are at:
http://www.kerneloops.org/search.php?search=uart_flush_buffer

What happens is that, on closing the bluetooth tty,
the tty layer goes into the release_dev() function,
which first does a bunch of stuff, then sets the file->private_data to NULL,
does some more stuff  and then calls the ldisc close function. Which in this
case, is hci_uart_tty_close().

Now, hci_uart_tty_close() calls hci_uart_close() which clears some internal bit,
and then calls hci_uart_flush()... which calls back to the tty layers' uart_flush_buffer() function.
(in drivers/bluetooth/hci_tty.c around line 194)
Which then WARN_ON()'s because that's not allowed/supposed to be called
this late in the shutdown of the port....

should the bluetooth driver even call this flush function at all??

Greetings,
    Arjan van de Ven

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