From 11dbf203922dc70a340417c895c95fb96f6b7068 Mon Sep 17 00:00:00 2001
From: Arnd Bergmann <arnd@arndb.de>
Date: Fri, 18 Jun 2010 14:58:07 +0200
Subject: tty: avoid recursive BTM in pty_close

When the console has been redirected, a hangup of the tty
will cause tty_release to be called under the big tty_mutex,
which leads to a deadlock because hangup is also called
under the BTM.

This moves the BTM deeper into the tty_hangup function so
we can close the redirected tty without holding the BTM.
In case of pty, we now need to drop the BTM before
calling tty_vhangup.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: John Kacur <jkacur@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
 drivers/char/pty.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

(limited to 'drivers/char/pty.c')

diff --git a/drivers/char/pty.c b/drivers/char/pty.c
index f2d7a76fab54..ad46eae1f9bb 100644
--- a/drivers/char/pty.c
+++ b/drivers/char/pty.c
@@ -62,7 +62,9 @@ static void pty_close(struct tty_struct *tty, struct file *filp)
 		if (tty->driver == ptm_driver)
 			devpts_pty_kill(tty->link);
 #endif
-		tty_vhangup_locked(tty->link);
+		tty_unlock();
+		tty_vhangup(tty->link);
+		tty_lock();
 	}
 }
 
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