[PATCH 06/10] tty: annotate tty_write_lock

From: Arnd Bergmann <arnd@arndb.de>
To: linux-kernel@vger.kernel.org
Cc: Arnd Bergmann <arnd@arndb.de>,
	Alan Cox <alan@lxorguk.ukuu.org.uk>, Greg KH <gregkh@suse.de>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	John Kacur <jkacur@redhat.com>, Al Viro <viro@zeniv.linux.org.uk>,
	Ingo Molnar <mingo@elte.hu>
Subject: [PATCH 06/10] tty: annotate tty_write_lock
Date: Sat, 15 May 2010 22:59:52 +0200	[thread overview]
Message-ID: <1273957196-13768-7-git-send-email-arnd@arndb.de> (raw)
In-Reply-To: <1273957196-13768-1-git-send-email-arnd@arndb.de>

atomic_write_lock never nests below BTM, so
there are no lock order problems between the
two.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/char/tty_io.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index d51993b..36aecba 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -912,6 +912,11 @@ void tty_write_unlock(struct tty_struct *tty)
 
 int tty_write_lock(struct tty_struct *tty, int ndelay)
 {
+	/*
+	 * code inspection has shown that this is never called
+	 * with the BTM held. Make sure this stays that way.
+	 */
+	WARN_ON_ONCE(tty_locked());
 	if (!mutex_trylock(&tty->atomic_write_lock)) {
 		if (ndelay)
 			return -EAGAIN;
-- 
1.7.0.4

