Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932777Ab2EVB7I (ORCPT ); Mon, 21 May 2012 21:59:08 -0400 Received: from mail-pz0-f46.google.com ([209.85.210.46]:42334 "EHLO mail-pz0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755942Ab2EVB7F (ORCPT ); Mon, 21 May 2012 21:59:05 -0400 From: Ming Lei To: Greg Kroah-Hartman Cc: linux-kernel@vger.kernel.org, Ming Lei , Alan Cox , Arnd Bergmann , Peter Zijlstra Subject: [PATCH] tty: tty_mutex: fix lockdep warning in tty_lock_pair(v1) Date: Tue, 22 May 2012 09:58:51 +0800 Message-Id: <1337651931-5301-1-git-send-email-ming.lei@canonical.com> X-Mailer: git-send-email 1.7.9.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1982 Lines: 70 Commit d29f3ef39be4eec0362b985305fc526d9be318cf(tty_lock: Localise the lock) introduces tty_lock_pair, in which may cause lockdep warning because two locks with same lock class are to be acquired one after another. This patch uses mutex_lock_nested annotation to avoid the warning as suggested by Peter. Cc: Alan Cox Cc: Arnd Bergmann Signed-off-by: Peter Zijlstra Signed-off-by: Ming Lei --- drivers/tty/tty_mutex.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) diff --git a/drivers/tty/tty_mutex.c b/drivers/tty/tty_mutex.c index 69adc80..fecf592 100644 --- a/drivers/tty/tty_mutex.c +++ b/drivers/tty/tty_mutex.c @@ -10,7 +10,8 @@ * Getting the big tty mutex. */ -void __lockfunc tty_lock(struct tty_struct *tty) +static void __lockfunc tty_lock_nested(struct tty_struct *tty, + int subclass) { if (tty->magic != TTY_MAGIC) { printk(KERN_ERR "L Bad %p\n", tty); @@ -18,7 +19,12 @@ void __lockfunc tty_lock(struct tty_struct *tty) return; } tty_kref_get(tty); - mutex_lock(&tty->legacy_mutex); + mutex_lock_nested(&tty->legacy_mutex, subclass); +} + +void __lockfunc tty_lock(struct tty_struct *tty) +{ + tty_lock_nested(tty, 0); } EXPORT_SYMBOL(tty_lock); @@ -43,11 +49,14 @@ void __lockfunc tty_lock_pair(struct tty_struct *tty, { if (tty < tty2) { tty_lock(tty); - tty_lock(tty2); + tty_lock_nested(tty2, SINGLE_DEPTH_NESTING); } else { - if (tty2 && tty2 != tty) + int nested = 0; + if (tty2 && tty2 != tty) { tty_lock(tty2); - tty_lock(tty); + nested = SINGLE_DEPTH_NESTING; + } + tty_lock_nested(tty, nested); } } EXPORT_SYMBOL(tty_lock_pair); -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/