linux-kernel - hci_ldsic nested locking problem

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Message-ID: <20140320163435.GH32692@saruman.home>
Date:	Thu, 20 Mar 2014 11:34:35 -0500
From:	Felipe Balbi <balbi@...com>
To:	Marcel Holtmann <marcel@...tmann.org>,
	Alan Cox <alan@...ux.intel.com>,
	Greg KH <gregkh@...uxfoundation.org>
CC:	Muralidharan Karicheri <m-karicheri2@...com>,
	<linux-bluetooth@...r.kernel.org>, <linux-serial@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: hci_ldsic nested locking problem

Hi,

when 8250 driver calls uart_write_wakeup(), the tty port lock is already
taken. hci_ldisc.c's implementation of ->write_wakeup() calls
tty->ops->write() to actually send the characters, but that call will
try to acquire the same port lock again.

Looking at other line disciplines that looks like a bug in hci_ldisc.c.
Am I correct to assume that ->write_wakeup() is supposed to *just*
wakeup the bottom half so we handle ->write() in another context ?

Is it legal to call tty->ops->write() from within ->write_wakeup() ?

cheers

-- 
balbi

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