From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: [PATCH] 6pack,mkiss: fix lock inconsistency Date: Fri, 1 Jul 2011 23:28:46 +0200 Message-ID: <201107012328.46256.arnd@arndb.de> References: <4B2CD772.1030106@upmc.fr> <20110625163942.GB20976@linux-mips.org> <4E0DC4F3.6010203@free.fr> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4E0DC4F3.6010203@free.fr> Sender: linux-hams-owner@vger.kernel.org List-ID: Content-Type: Text/Plain; charset="us-ascii" To: Bernard F6BVP , David Miller Cc: Ralf Baechle DL5RB , linux-kernel@vger.kernel.org, Linux Netdev List , linux-hams@vger.kernel.org Lockdep found a locking inconsistency in the mkiss_close function: > kernel: [ INFO: inconsistent lock state ] > kernel: 2.6.39.1 #3 > kernel: --------------------------------- > kernel: inconsistent {IN-SOFTIRQ-R} -> {SOFTIRQ-ON-W} usage. > kernel: ax25ipd/2813 [HC0[0]:SC0[0]:HE1:SE1] takes: > kernel: (disc_data_lock){+++?.-}, at: [] mkiss_close+0x1b/0x90 [mkiss] > kernel: {IN-SOFTIRQ-R} state was registered at: The message hints that disc_data_lock is aquired with softirqs disabled, but does not itself disable softirqs, which can in rare circumstances lead to a deadlock. The same problem is present in the 6pack driver, this patch fixes both by using write_lock_bh instead of write_lock. Reported-by: Bernard F6BVP Tested-by: Bernard F6BVP Signed-off-by: Arnd Bergmann Acked-by: Ralf Baechle Cc: stable@kernel.org --- On Friday 01 July 2011 15:00:35 Bernard F6BVP wrote: > > Now, who is going to commit this mkiss patch and the equivalent one for > sixpack.c ? Here's a formal patch with all the right tags, I assume that David Miller will apply that to the netdev tree. diff --git a/drivers/net/hamradio/6pack.c b/drivers/net/hamradio/6pack.c index 9624cbf..fea7cb4 100644 --- a/drivers/net/hamradio/6pack.c +++ b/drivers/net/hamradio/6pack.c @@ -694,10 +694,10 @@ static void sixpack_close(struct tty_struct *tty) { struct sixpack *sp; - write_lock(&disc_data_lock); + write_lock_bh(&disc_data_lock); sp = tty->disc_data; tty->disc_data = NULL; - write_unlock(&disc_data_lock); + write_unlock_bh(&disc_data_lock); if (!sp) return; diff --git a/drivers/net/hamradio/mkiss.c b/drivers/net/hamradio/mkiss.c index 9f84c83..324f7bf 100644 --- a/drivers/net/hamradio/mkiss.c +++ b/drivers/net/hamradio/mkiss.c @@ -813,10 +813,10 @@ static void mkiss_close(struct tty_struct *tty) { struct mkiss *ax; - write_lock(&disc_data_lock); + write_lock_bh(&disc_data_lock); ax = tty->disc_data; tty->disc_data = NULL; - write_unlock(&disc_data_lock); + write_unlock_bh(&disc_data_lock); if (!ax) return;