From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759189AbYENBsS (ORCPT ); Tue, 13 May 2008 21:48:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752173AbYENBsE (ORCPT ); Tue, 13 May 2008 21:48:04 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:50235 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751774AbYENBsB (ORCPT ); Tue, 13 May 2008 21:48:01 -0400 Date: Tue, 13 May 2008 18:47:36 -0700 From: Andrew Morton To: Marcin Slusarz Cc: LKML , Alan Cox , Alexander Viro , Oleg Nesterov Subject: Re: [vfs/tty] possible circular locking dependency detected Message-Id: <20080513184736.a385ffe2.akpm@linux-foundation.org> In-Reply-To: <20080512183235.GB6031@joi> References: <20080512183235.GB6031@joi> X-Mailer: Sylpheed 2.4.8 (GTK+ 2.12.5; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 12 May 2008 20:32:59 +0200 Marcin Slusarz wrote: > May 11 08:52:08 [kernel] [ 21.052750] Clocksource tsc unstable (delta = -109466779 ns) > May 11 09:42:27 [kernel] [ 1104.496819] rarian-sk-get-c[5630]: segfault at 0 ip 7f478556caf0 sp 7fff8e3fe338 error 4 in libc-2.6.1.so[7f47854f9000+136000] > May 11 10:59:48 [kernel] [ 2494.165792] > May 11 10:59:48 [kernel] [ 2494.165794] ======================================================= > May 11 10:59:48 [kernel] [ 2494.165801] [ INFO: possible circular locking dependency detected ] > May 11 10:59:48 [kernel] [ 2494.165805] 2.6.26-rc1-00007-g91b3a7a #217 > May 11 10:59:48 [kernel] [ 2494.165807] ------------------------------------------------------- > May 11 10:59:48 [kernel] [ 2494.165809] less/7053 is trying to acquire lock: > May 11 10:59:48 [kernel] [ 2494.165812] (tasklist_lock){..??}, at: [] is_current_pgrp_orphaned+0x15/0x50 > May 11 10:59:48 [kernel] [ 2494.165821] > May 11 10:59:48 [kernel] [ 2494.165822] but task is already holding lock: > May 11 10:59:48 [kernel] [ 2494.165824] (&tty->ctrl_lock){....}, at: [] tty_check_change+0x61/0x110 > May 11 10:59:48 [kernel] [ 2494.165831] > May 11 10:59:48 [kernel] [ 2494.165832] which lock already depends on the new lock. > May 11 10:59:48 [kernel] [ 2494.165833] > May 11 10:59:48 [kernel] [ 2494.165835] > May 11 10:59:48 [kernel] [ 2494.165836] the existing dependency chain (in reverse order) is: > May 11 10:59:48 [kernel] [ 2494.165838] > May 11 10:59:48 [kernel] [ 2494.165839] -> #2 (&tty->ctrl_lock){....}: > May 11 10:59:48 [kernel] [ 2494.165843] [] __lock_acquire+0xf86/0x1080 > May 11 10:59:48 [kernel] [ 2494.165851] [] lock_acquire+0x92/0xc0 > May 11 10:59:48 [kernel] [ 2494.165858] [] _spin_lock_irqsave+0x40/0x60 > May 11 10:59:48 [kernel] [ 2494.165866] [] __proc_set_tty+0x35/0xe0 > May 11 10:59:48 [kernel] [ 2494.165873] [] tty_ioctl+0xbf4/0xfe0 > May 11 10:59:48 [kernel] [ 2494.165880] [] vfs_ioctl+0x31/0x90 > May 11 10:59:48 [kernel] [ 2494.165888] [] do_vfs_ioctl+0x73/0x2d0 > May 11 10:59:48 [kernel] [ 2494.165895] [] sys_ioctl+0x4a/0x80 > May 11 10:59:48 [kernel] [ 2494.165902] [] system_call_after_swapgs+0x7b/0x80 > May 11 10:59:48 [kernel] [ 2494.165910] [] 0xffffffffffffffff > May 11 10:59:48 [kernel] [ 2494.165924] > May 11 10:59:48 [kernel] [ 2494.165925] -> #1 (&sighand->siglock){++..}: > May 11 10:59:48 [kernel] [ 2494.165929] [] __lock_acquire+0xf86/0x1080 > May 11 10:59:48 [kernel] [ 2494.165936] [] lock_acquire+0x92/0xc0 > May 11 10:59:48 [kernel] [ 2494.165943] [] _spin_lock+0x2f/0x40 > May 11 10:59:48 [kernel] [ 2494.165951] [] copy_process+0x973/0x1210 > May 11 10:59:48 [kernel] [ 2494.165959] [] do_fork+0x82/0x2f0 > May 11 10:59:48 [kernel] [ 2494.165967] [] kernel_thread+0x81/0xde > May 11 10:59:48 [kernel] [ 2494.165974] [] child_rip+0xa/0x12 > May 11 10:59:48 [kernel] [ 2494.165981] [] 0xffffffffffffffff > May 11 10:59:48 [kernel] [ 2494.166038] > May 11 10:59:48 [kernel] [ 2494.166039] -> #0 (tasklist_lock){..??}: > May 11 10:59:48 [kernel] [ 2494.166043] [] __lock_acquire+0xd9b/0x1080 > May 11 10:59:48 [kernel] [ 2494.166050] [] lock_acquire+0x92/0xc0 > May 11 10:59:48 [kernel] [ 2494.166057] [] _read_lock+0x32/0x50 > May 11 10:59:48 [kernel] [ 2494.166063] [] is_current_pgrp_orphaned+0x15/0x50 > May 11 10:59:48 [kernel] [ 2494.166071] [] tty_check_change+0xb0/0x110 > May 11 10:59:48 [kernel] [ 2494.166078] [] set_termios+0x1f/0x4c0 > May 11 10:59:48 [kernel] [ 2494.166085] [] tty_mode_ioctl+0x279/0x3e0 > May 11 10:59:48 [kernel] [ 2494.166092] [] n_tty_ioctl+0x3d/0x260 > May 11 10:59:48 [kernel] [ 2494.166100] [] tty_ioctl+0x154/0xfe0 > May 11 10:59:48 [kernel] [ 2494.166107] [] vfs_ioctl+0x31/0x90 > May 11 10:59:48 [kernel] [ 2494.166114] [] do_vfs_ioctl+0x73/0x2d0 > May 11 10:59:48 [kernel] [ 2494.166121] [] sys_ioctl+0x4a/0x80 > May 11 10:59:48 [kernel] [ 2494.166128] [] system_call_after_swapgs+0x7b/0x80 > May 11 10:59:48 [kernel] [ 2494.166135] [] 0xffffffffffffffff > May 11 10:59:48 [kernel] [ 2494.166142] > May 11 10:59:48 [kernel] [ 2494.166143] other info that might help us debug this: > May 11 10:59:48 [kernel] [ 2494.166144] > May 11 10:59:48 [kernel] [ 2494.166146] 1 lock held by less/7053: > May 11 10:59:48 [kernel] [ 2494.166148] #0: (&tty->ctrl_lock){....}, at: [] tty_check_change+0x61/0x110 > May 11 10:59:48 [kernel] [ 2494.166155] > May 11 10:59:48 [kernel] [ 2494.166156] stack backtrace: > May 11 10:59:48 [kernel] [ 2494.166159] Pid: 7053, comm: less Not tainted 2.6.26-rc1-00007-g91b3a7a #217 > May 11 10:59:48 [kernel] [ 2494.166161] > May 11 10:59:48 [kernel] [ 2494.166162] Call Trace: > May 11 10:59:48 [kernel] [ 2494.166168] [] print_circular_bug_tail+0x83/0x90 > May 11 10:59:48 [kernel] [ 2494.166172] [] ? print_circular_bug_entry+0x49/0x60 > May 11 10:59:48 [kernel] [ 2494.166178] [] __lock_acquire+0xd9b/0x1080 > May 11 10:59:48 [kernel] [ 2494.166184] [] ? is_current_pgrp_orphaned+0x15/0x50 > May 11 10:59:48 [kernel] [ 2494.166189] [] lock_acquire+0x92/0xc0 > May 11 10:59:48 [kernel] [ 2494.166206] [] tty_check_change+0xb0/0x110 > May 11 10:59:48 [kernel] [ 2494.166211] [] set_termios+0x1f/0x4c0 > May 11 10:59:48 [kernel] [ 2494.166216] [] ? tty_ldisc_try+0x23/0x60 > May 11 10:59:48 [kernel] [ 2494.166220] [] ? tty_ldisc_try+0x44/0x60 > May 11 10:59:48 [kernel] [ 2494.166224] [] ? _spin_unlock_irqrestore+0x65/0x80 > May 11 10:59:48 [kernel] [ 2494.166230] [] tty_mode_ioctl+0x279/0x3e0 > May 11 10:59:48 [kernel] [ 2494.166234] [] ? tty_ldisc_try+0x44/0x60 > May 11 10:59:48 [kernel] [ 2494.166239] [] n_tty_ioctl+0x3d/0x260 > May 11 10:59:48 [kernel] [ 2494.166244] [] tty_ioctl+0x154/0xfe0 > May 11 10:59:48 [kernel] [ 2494.166249] [] ? __lock_acquire+0x39a/0x1080 > May 11 10:59:48 [kernel] [ 2494.166256] [] ? __lock_acquire+0x39a/0x1080 > May 11 10:59:48 [kernel] [ 2494.166263] [] ? __lock_acquire+0x39a/0x1080 > May 11 10:59:48 [kernel] [ 2494.166269] [] vfs_ioctl+0x31/0x90 > May 11 10:59:48 [kernel] [ 2494.166274] [] do_vfs_ioctl+0x73/0x2d0 > May 11 10:59:48 [kernel] [ 2494.166280] [] sys_ioctl+0x4a/0x80 > May 11 10:59:48 [kernel] [ 2494.166286] [] system_call_after_swapgs+0x7b/0x80 > May 11 10:59:48 [kernel] [ 2494.166292] > > It was on 2.6.26-rc1 + some patches (afa26be86b65a7183ceac29bdf1f51d6fc6932f0) > I think it had something to do with a hang of my yakuake (KDE terminal emulator) session. > But I'm not sure (I noticed this warning much later) Bummer. I don't immediately see any reason why the ctrl_lock coverage in tty_check_change() needs to be as broad as it is? But then it's one of those super-secret-who-knows-what-it-does locks :( It seems to be protecting ->session and ->pgrp. This, perhaps... --- a/drivers/char/tty_io.c~a +++ a/drivers/char/tty_io.c @@ -1215,10 +1215,11 @@ int tty_check_change(struct tty_struct * if (!tty->pgrp) { printk(KERN_WARNING "tty_check_change: tty->pgrp == NULL!\n"); - goto out; + goto out_unlock; } if (task_pgrp(current) == tty->pgrp) - goto out; + goto out_unlock; + spin_unlock_irqrestore(&tty->ctrl_lock, flags); if (is_ignored(SIGTTOU)) goto out; if (is_current_pgrp_orphaned()) { @@ -1229,6 +1230,8 @@ int tty_check_change(struct tty_struct * set_thread_flag(TIF_SIGPENDING); ret = -ERESTARTSYS; out: + return ret; +out_unlock: spin_unlock_irqrestore(&tty->ctrl_lock, flags); return ret; } _