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Date: Mon, 21 Mar 2011 08:43:59 +0000
From: "Ferraton, Jean RegisX" <jean.regisx.ferraton@...el.com>
To: "Gustavo F. Padovan" <padovan@...fusion.mobi>
CC: "marcel@...tmann.org" <marcel@...tmann.org>,
"davem@...emloft.net" <davem@...emloft.net>,
"eric.dumazet@...il.com" <eric.dumazet@...il.com>,
"xiaosuo@...il.com" <xiaosuo@...il.com>,
"linux-bluetooth@...r.kernel.org" <linux-bluetooth@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH] Fix "possible circular locking dependency" in rfcomm
Any comment?
> -----Original Message-----
> From: linux-bluetooth-owner@...r.kernel.org [mailto:linux-bluetooth-
> owner@...r.kernel.org] On Behalf Of Ferraton, Jean RegisX
> Sent: Monday, March 14, 2011 3:56 PM
> To: Gustavo F. Padovan
> Cc: marcel@...tmann.org; davem@...emloft.net; eric.dumazet@...il.com;
> xiaosuo@...il.com; linux-bluetooth@...r.kernel.org; linux-
> kernel@...r.kernel.org; netdev@...r.kernel.org
> Subject: [PATCH] Fix "possible circular locking dependency" in rfcomm
>
> No response from original post, submit again, more details below:
>
> Changes in sock.c in function __rfcomm_sock_close, to release sock before
> calling rfcomm_dlc_close to avoid possible deadlock when calling
> rfcomm_lock (in rfcomm_dlc_close).
>
> Signed-off-by: Jean Regis Ferraton <jrferraton@...il.com>
>
> ---
> net/bluetooth/rfcomm/sock.c | 3 +++
> 1 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c
> index 66cc1f0..3b5ec09 100644
> --- a/net/bluetooth/rfcomm/sock.c
> +++ b/net/bluetooth/rfcomm/sock.c
> @@ -234,7 +234,10 @@ static void __rfcomm_sock_close(struct sock *sk)
> case BT_CONNECT2:
> case BT_CONFIG:
> case BT_CONNECTED:
> + /* release_sock to avoid deadlock when calling rfcomm_lock()
> */
> + release_sock(sk);
> rfcomm_dlc_close(d, 0);
> + lock_sock(sk);
>
> default:
> sock_set_flag(sk, SOCK_ZAPPED);
> --
> 1.6.2.5
>
>
>
> This patch solves a problem of "possible circular locking dependency"
> related to rfcomm. Problem seen on kernel 2.6.37. Maybe it's not a bug,
> just a warning, see the trace below.
>
> This problem occurs in 2 cases:
> 1- When initiating a connection from the remote device
> 2- When browsing my BT device from my PC
>
> My analysis is the following:
> 1- We call the function rfcomm_sock_shutdown() which locks a socket, an
> after calls __rfcomm_sock_close()
> lock_sock(sk);
> if (!sk->sk_shutdown) {
> sk->sk_shutdown = SHUTDOWN_MASK;
> __rfcomm_sock_close(sk);
> 2- In the function __rfcomm_sock_close(), we call rfcomm_dlc_close()
> case BT_CONNECTED:
> rfcomm_dlc_close(d, 0);
> 3- In the function rfcomm_dlc_close(), we call rfcomm_lock() which locks a
> mutex on rfcomm, and this second lock causes the problem.
> rfcomm_lock();
> r = __rfcomm_dlc_close(d, err);
>
> My message trace is the following (for remote connect):
> [ 113.995511] =======================================================
> [ 114.001897] [ INFO: possible circular locking dependency detected ]
> [ 114.008157] 2.6.37.3jrf_fix #1
> [ 114.011196] -------------------------------------------------------
> [ 114.017457] bluetoothd/511 is trying to acquire lock:
> [ 114.022499] (rfcomm_mutex){+.+.+.}, at: [<c14f281a>]
> rfcomm_dlc_close+0x15/0x30
> [ 114.029887]
> [ 114.029892] but task is already holding lock:
> [ 114.035713] (sk_lock-AF_BLUETOOTH){+.+.+.}, at: [<c14f4cfe>]
> rfcomm_sock_shutdown+0x17/0x5d
> [ 114.044147]
> [ 114.044152] which lock already depends on the new lock.
> [ 114.044158]
> [ 114.052319]
> [ 114.052324] the existing dependency chain (in reverse order) is:
> [ 114.059796]
> [ 114.059801] -> #1 (sk_lock-AF_BLUETOOTH){+.+.+.}:
> [ 114.065967] [<c105d660>] lock_acquire+0xf9/0x135
> [ 114.071184] [<c1445cf3>] lock_sock_nested+0x55/0x65
> [ 114.076662] [<c14ed17d>] l2cap_sock_sendmsg+0x3f/0x606
> [ 114.082400] [<c1443775>] sock_sendmsg+0xc9/0xe0
> [ 114.087530] [<c14437b4>] kernel_sendmsg+0x28/0x37
> [ 114.092833] [<c14f2278>] rfcomm_send_frame+0x2f/0x37
> [ 114.098398] [<c14f232c>] rfcomm_send_ua+0x57/0x59
> [ 114.103701] [<c14f3884>] rfcomm_run+0x431/0xb06
> [ 114.108830] [<c104bc8f>] kthread+0x5f/0x64
> [ 114.113525] [<c1002b7a>] kernel_thread_helper+0x6/0x1a
> [ 114.119265]
> [ 114.119270] -> #0 (rfcomm_mutex){+.+.+.}:
> [ 114.124739] [<c105cff1>] __lock_acquire+0xe03/0x1379
> [ 114.130304] [<c105d660>] lock_acquire+0xf9/0x135
> [ 114.135522] [<c1522bf3>] mutex_lock_nested+0x45/0x286
> [ 114.141171] [<c14f281a>] rfcomm_dlc_close+0x15/0x30
> [ 114.146650] [<c14f4cdb>] __rfcomm_sock_close+0x5e/0x6a
> [ 114.152388] [<c14f4d12>] rfcomm_sock_shutdown+0x2b/0x5d
> [ 114.158212] [<c14f4d5d>] rfcomm_sock_release+0x19/0x60
> [ 114.163951] [<c14445da>] sock_release+0x14/0x5b
> [ 114.169080] [<c144463d>] sock_close+0x1c/0x20
> [ 114.174037] [<c10bdd19>] fput+0xfa/0x19e
> [ 114.178557] [<c10bb3c5>] filp_close+0x51/0x5b
> [ 114.183512] [<c10bb488>] sys_close+0xb9/0xee
> [ 114.188381] [<c1002650>] sysenter_do_call+0x12/0x36
> [ 114.193858]
> [ 114.193863] other info that might help us debug this:
> [ 114.193870]
> [ 114.201860] 1 lock held by bluetoothd/511:
> [ 114.205945] #0: (sk_lock-AF_BLUETOOTH){+.+.+.}, at: [<c14f4cfe>]
> rfcomm_sock_shutdown+0x17/0x5d
> [ 114.214811]
> [ 114.214816] stack backtrace:
> [ 114.219167] Pid: 511, comm: bluetoothd Tainted: G WC
> 2.6.37.3jrf_fix #1
> [ 114.226463] Call Trace:
> [ 114.228913] [<c152108a>] ? printk+0xf/0x11
> [ 114.233086] [<c105bc3b>] print_circular_bug+0x90/0x9c
> [ 114.238211] [<c105cff1>] __lock_acquire+0xe03/0x1379
> [ 114.243260] [<c14f281a>] ? rfcomm_dlc_close+0x15/0x30
> [ 114.248382] [<c105d660>] lock_acquire+0xf9/0x135
> [ 114.253079] [<c14f281a>] ? rfcomm_dlc_close+0x15/0x30
> [ 114.258208] [<c1522bf3>] mutex_lock_nested+0x45/0x286
> [ 114.263338] [<c14f281a>] ? rfcomm_dlc_close+0x15/0x30
> [ 114.268469] [<c105b68d>] ? trace_hardirqs_on_caller+0x100/0x121
> [ 114.274467] [<c1445cf8>] ? lock_sock_nested+0x5a/0x65
> [ 114.279597] [<c105b6b9>] ? trace_hardirqs_on+0xb/0xd
> [ 114.284639] [<c14f281a>] rfcomm_dlc_close+0x15/0x30
> [ 114.289594] [<c14f4cdb>] __rfcomm_sock_close+0x5e/0x6a
> [ 114.294811] [<c14f4d12>] rfcomm_sock_shutdown+0x2b/0x5d
> [ 114.300115] [<c14f4d5d>] rfcomm_sock_release+0x19/0x60
> [ 114.305331] [<c14445da>] sock_release+0x14/0x5b
> [ 114.309937] [<c144463d>] sock_close+0x1c/0x20
> [ 114.314373] [<c10bdd19>] fput+0xfa/0x19e
> [ 114.318371] [<c10bb3c5>] filp_close+0x51/0x5b
> [ 114.322804] [<c10bb488>] sys_close+0xb9/0xee
> [ 114.327151] [<c1002650>] sysenter_do_call+0x12/0x36
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Intel Corporation SAS (French simplified joint stock company)
Registered headquarters: "Les Montalets"- 2, rue de Paris,
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Registration Number: 302 456 199 R.C.S. NANTERRE
Capital: 4,572,000 Euros
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