Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S932122Ab2BHMly (ORCPT <rfc822;w@1wt.eu>);
	Wed, 8 Feb 2012 07:41:54 -0500
Received: from na3sys009aog119.obsmtp.com ([74.125.149.246]:35348 "EHLO
	na3sys009aog119.obsmtp.com" rhost-flags-OK-OK-OK-OK)
	by vger.kernel.org with ESMTP id S932090Ab2BHMlw (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Wed, 8 Feb 2012 07:41:52 -0500
Date: Wed, 8 Feb 2012 14:41:48 +0200
From: Felipe Balbi <balbi@ti.com>
To: Grant Likely <grant.likely@secretlab.ca>,
        Linus Walleij <linus.walleij@stericsson.com>
Cc: Linux OMAP Mailing List <linux-omap@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux ARM Kernel Mailing List 
	<linux-arm-kernel@lists.infradead.org>
Subject: Possible circular locking dependency (3.3-rc2)
Message-ID: <20120208124147.GF16334@legolas.emea.dhcp.ti.com>
Reply-To: balbi@ti.com
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha1;
	protocol="application/pgp-signature"; boundary="jkO+KyKz7TfD21mV"
Content-Disposition: inline
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 6763
Lines: 152


--jkO+KyKz7TfD21mV
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

Hi guys,

I have just triggered the folllowing:

[   84.860321] =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D
[   84.860321] [ INFO: possible circular locking dependency detected ]
[   84.860321] 3.3.0-rc2-00026-ge4e8a39 #474 Not tainted
[   84.860321] -------------------------------------------------------
[   84.860321] bash/949 is trying to acquire lock:
[   84.860321]  (sysfs_lock){+.+.+.}, at: [<c0275358>] gpio_value_store+0x2=
4/0xcc
[   84.860321]=20
[   84.860321] but task is already holding lock:
[   84.860321]  (s_active#22){++++.+}, at: [<c016996c>] sysfs_write_file+0x=
dc/0x184
[   84.911468]=20
[   84.911468] which lock already depends on the new lock.
[   84.911468]=20
[   84.920043]=20
[   84.920043] the existing dependency chain (in reverse order) is:
[   84.920043]=20
[   84.927886] -> #1 (s_active#22){++++.+}:
[   84.927886]        [<c008f640>] check_prevs_add+0xdc/0x150
[   84.927886]        [<c008fc18>] validate_chain.clone.24+0x564/0x694
[   84.927886]        [<c0090cdc>] __lock_acquire+0x49c/0x980
[   84.951660]        [<c0091838>] lock_acquire+0x98/0x100
[   84.951660]        [<c016a8e8>] sysfs_deactivate+0xb0/0x100
[   84.962982]        [<c016b1b4>] sysfs_addrm_finish+0x2c/0x6c
[   84.962982]        [<c016b8bc>] sysfs_remove_dir+0x84/0x98
[   84.962982]        [<c02590d8>] kobject_del+0x10/0x78
[   84.974670]        [<c02c29e8>] device_del+0x140/0x170
[   84.974670]        [<c02c2a24>] device_unregister+0xc/0x18
[   84.985382]        [<c0276894>] gpio_unexport+0xbc/0xdc
[   84.985382]        [<c02768c8>] gpio_free+0x14/0xfc
[   85.001708]        [<c0276a28>] unexport_store+0x78/0x8c
[   85.001708]        [<c02c5af8>] class_attr_store+0x18/0x24
[   85.007293]        [<c0169990>] sysfs_write_file+0x100/0x184
[   85.018981]        [<c0109d48>] vfs_write+0xb4/0x148
[   85.018981]        [<c0109fd0>] sys_write+0x40/0x70
[   85.018981]        [<c0013cc0>] ret_fast_syscall+0x0/0x3c
[   85.035003]=20
[   85.035003] -> #0 (sysfs_lock){+.+.+.}:
[   85.035003]        [<c008f54c>] check_prev_add+0x680/0x698
[   85.035003]        [<c008f640>] check_prevs_add+0xdc/0x150
[   85.052093]        [<c008fc18>] validate_chain.clone.24+0x564/0x694
[   85.052093]        [<c0090cdc>] __lock_acquire+0x49c/0x980
[   85.052093]        [<c0091838>] lock_acquire+0x98/0x100
[   85.069885]        [<c047e280>] mutex_lock_nested+0x3c/0x2f4
[   85.069885]        [<c0275358>] gpio_value_store+0x24/0xcc
[   85.069885]        [<c02c18dc>] dev_attr_store+0x18/0x24
[   85.087158]        [<c0169990>] sysfs_write_file+0x100/0x184
[   85.087158]        [<c0109d48>] vfs_write+0xb4/0x148
[   85.098297]        [<c0109fd0>] sys_write+0x40/0x70
[   85.098297]        [<c0013cc0>] ret_fast_syscall+0x0/0x3c
[   85.109069]=20
[   85.109069] other info that might help us debug this:
[   85.109069]=20
[   85.117462]  Possible unsafe locking scenario:
[   85.117462]=20
[   85.117462]        CPU0                    CPU1
[   85.128417]        ----                    ----
[   85.128417]   lock(s_active#22);
[   85.128417]                                lock(sysfs_lock);
[   85.128417]                                lock(s_active#22);
[   85.142486]   lock(sysfs_lock);
[   85.151794]=20
[   85.151794]  *** DEADLOCK ***
[   85.151794]=20
[   85.151794] 2 locks held by bash/949:
[   85.158020]  #0:  (&buffer->mutex){+.+.+.}, at: [<c01698b8>] sysfs_write=
_file+0x28/0x184
[   85.170349]  #1:  (s_active#22){++++.+}, at: [<c016996c>] sysfs_write_fi=
le+0xdc/0x184
[   85.170349]=20
[   85.178588] stack backtrace:
[   85.178588] [<c001b824>] (unwind_backtrace+0x0/0xf0) from [<c008de64>] (=
print_circular_bug+0x100/0x114)
[   85.193023] [<c008de64>] (print_circular_bug+0x100/0x114) from [<c008f54=
c>] (check_prev_add+0x680/0x698)
[   85.193023] [<c008f54c>] (check_prev_add+0x680/0x698) from [<c008f640>] =
(check_prevs_add+0xdc/0x150)
[   85.212524] [<c008f640>] (check_prevs_add+0xdc/0x150) from [<c008fc18>] =
(validate_chain.clone.24+0x564/0x694)
[   85.212524] [<c008fc18>] (validate_chain.clone.24+0x564/0x694) from [<c0=
090cdc>] (__lock_acquire+0x49c/0x980)
[   85.233306] [<c0090cdc>] (__lock_acquire+0x49c/0x980) from [<c0091838>] =
(lock_acquire+0x98/0x100)
[   85.233306] [<c0091838>] (lock_acquire+0x98/0x100) from [<c047e280>] (mu=
tex_lock_nested+0x3c/0x2f4)
[   85.242614] [<c047e280>] (mutex_lock_nested+0x3c/0x2f4) from [<c0275358>=
] (gpio_value_store+0x24/0xcc)
[   85.261840] [<c0275358>] (gpio_value_store+0x24/0xcc) from [<c02c18dc>] =
(dev_attr_store+0x18/0x24)
[   85.261840] [<c02c18dc>] (dev_attr_store+0x18/0x24) from [<c0169990>] (s=
ysfs_write_file+0x100/0x184)
[   85.271240] [<c0169990>] (sysfs_write_file+0x100/0x184) from [<c0109d48>=
] (vfs_write+0xb4/0x148)
[   85.290008] [<c0109d48>] (vfs_write+0xb4/0x148) from [<c0109fd0>] (sys_w=
rite+0x40/0x70)
[   85.298400] [<c0109fd0>] (sys_write+0x40/0x70) from [<c0013cc0>] (ret_fa=
st_syscall+0x0/0x3c)
-bash: echo: write error: Operation not permitted

the way to trigger is:


root@legolas:~# cd /sys/class/gpio/
root@legolas:/sys/class/gpio# echo 2 > export=20
root@legolas:/sys/class/gpio# echo 2 > unexport=20
root@legolas:/sys/class/gpio# echo 2 > export=20
root@legolas:/sys/class/gpio# cd gpio2/
root@legolas:/sys/class/gpio/gpio2# echo 1 > value=20

--=20
balbi

--jkO+KyKz7TfD21mV
Content-Type: application/pgp-signature; name="signature.asc"
Content-Description: Digital signature

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.11 (GNU/Linux)
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=4NF/
-----END PGP SIGNATURE-----

--jkO+KyKz7TfD21mV--
--
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/