From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751464Ab2EYEph (ORCPT ); Fri, 25 May 2012 00:45:37 -0400 Received: from e31.co.us.ibm.com ([32.97.110.149]:59412 "EHLO e31.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750850Ab2EYEpg (ORCPT ); Fri, 25 May 2012 00:45:36 -0400 Message-ID: <4FBF0DF9.5040806@linaro.org> Date: Thu, 24 May 2012 21:43:37 -0700 From: John Stultz User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:11.0) Gecko/20120410 Thunderbird/11.0.1 MIME-Version: 1.0 To: Alan Cox CC: Jiri Slaby , lkml Subject: tty_lock lockdep warning Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12052504-7282-0000-0000-0000095264D3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hey Alan, I've been seeing the following lockdep warning w/ Linus' 3.5-rc HEAD from today. This is running x86_64 in a kvm environment. Let me know if there are any other details you'd like from me. thanks -john ============================================= [ INFO: possible recursive locking detected ] 3.4.0john+ #347 Not tainted --------------------------------------------- plymouthd/1345 is trying to acquire lock: (&tty->legacy_mutex){+.+.+.}, at: [] tty_lock+0x61/0xb0 but task is already holding lock: (&tty->legacy_mutex){+.+.+.}, at: [] tty_lock+0x61/0xb0 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&tty->legacy_mutex); lock(&tty->legacy_mutex); *** DEADLOCK *** May be due to missing lock nesting notation 2 locks held by plymouthd/1345: #0: (tty_mutex){+.+.+.}, at: [] tty_release+0x1e2/0x600 #1: (&tty->legacy_mutex){+.+.+.}, at: [] tty_lock+0x61/0xb0 stack backtrace: Pid: 1345, comm: plymouthd Not tainted 3.4.0john+ #347 Call Trace: [] ? vprintk_emit+0x287/0x5d0 [] validate_chain+0xf36/0x1380 [] ? sched_clock_local+0x43/0xb0 [] ? local_clock+0x6f/0x80 [] ? trace_hardirqs_off_caller+0x29/0x140 [] __lock_acquire+0x43e/0xb80 [] lock_acquire+0xb1/0x210 [] ? tty_lock+0x61/0xb0 [] mutex_lock_nested+0x73/0x4b0 [] ? tty_lock+0x61/0xb0 [] ? tty_lock+0x61/0xb0 [] tty_lock+0x61/0xb0 [] tty_lock_pair+0x5d/0x64 [] tty_release+0x1ed/0x600 [] fput+0x138/0x2e0 [] tty_ioctl+0xb68/0xd40 [] ? _raw_spin_unlock_irqrestore+0x71/0xa0 [] do_vfs_ioctl+0xa4/0x5c0 [] ? put_ldisc+0x11c/0x190 [] ? tty_ldisc_deref+0xe/0x10 [] ? tty_compat_ioctl+0xc7/0xf0 [] compat_sys_ioctl+0x257/0x1220 [] ? sysenter_dispatch+0x19/0x26 [] ? trace_hardirqs_off_thunk+0x3a/0x3c [] sysenter_dispatch+0x7/0x26 [] ? trace_hardirqs_on_thunk+0x3a/0x3f