Hi Gustavo
If we use the below patch, we face crash or circular locking dependency
detected.
*It's very easily reproduced(about 100%)
I guess once sco_sock_shutdown() is called,"sk" would be destructed.
but due to response from remote side, sco_disconn_cfm(),sco_conn_del()
would be called in order.
and finally in sco_conn_del() crash or circular locking dependency is
happened.
because it access "sk" that is already destructed.
I think in sco_chan_del(), based on conn info, the relation between sk
and conn should be cleaned
like the original code before you commit.
[ 104.889622] Bluetooth: [sco_sock_shutdown] sock e8856000, sk eb695000
[ 104.894666] Bluetooth: [sco_sock_clear_timer] sock eb695000 state 1
[ 104.900869] Bluetooth: [__sco_sock_close] sk eb695000 state 1 socket
e8856000
[ 104.907976] Bluetooth: [sco_sock_set_timer] sock eb695000 state 8
timeout 400
[ 104.915106] Bluetooth: [sco_sock_release] sock e8856000, sk eb695000
[ 104.921439] Bluetooth: [sco_sock_clear_timer] sock eb695000 state 8
[ 104.927875] Bluetooth: [__sco_sock_close] sk eb695000 state 8 socket
e8856000
[ 104.938762] Bluetooth: [sco_chan_del] sk eb695000, conn ed38da60, err 104
[ 104.956861] Bluetooth: [sco_sock_kill] sk eb695000 state 9
[ 104.962321] Bluetooth: [sco_sock_destruct] sk eb695000
[ 105.071125] Bluetooth: [sco_disconn_cfm] hcon ed376000 reason 22
[ 105.075875] Bluetooth: [sco_conn_del] hcon ed376000 conn ed38da60,
err 103
[ 105.082848] Bluetooth: [sco_conn_del] before bh_lock_sock () sk eb695000
Could you give me your opinion?
regards
chanyeol
On 06/15/2012 02:41 PM, Gustavo Padovan wrote:
From: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
sco_chan_del() only has conn != NULL when called from sco_conn_del() so
just move the code from it that deal with conn to sco_conn_del().
[ 120.765529]
[ 120.765529] ======================================================
[ 120.766529] [ INFO: possible circular locking dependency detected ]
[ 120.766529] 3.5.0-rc1-10292-g3701f94-dirty #70 Tainted: G W
[ 120.766529] -------------------------------------------------------
[ 120.766529] kworker/u:3/1497 is trying to acquire lock:
[ 120.766529] (&(&conn->lock)->rlock#2){+.+...}, at:
[<ffffffffa00b7ecc>] sco_chan_del+0x4c/0x170 [bluetooth]
[ 120.766529]
[ 120.766529] but task is already holding lock:
[ 120.766529] (slock-AF_BLUETOOTH-BTPROTO_SCO){+.+...}, at:
[<ffffffffa00b8401>] sco_conn_del+0x61/0xe0 [bluetooth]
[ 120.766529]
[ 120.766529] which lock already depends on the new lock.
[ 120.766529]
[ 120.766529]
[ 120.766529] the existing dependency chain (in reverse order) is:
[ 120.766529]
[ 120.766529] -> #1 (slock-AF_BLUETOOTH-BTPROTO_SCO){+.+...}:
[ 120.766529] [<ffffffff8107980e>] lock_acquire+0x8e/0xb0
[ 120.766529] [<ffffffff813c19e0>] _raw_spin_lock+0x40/0x80
[ 120.766529] [<ffffffffa00b85e9>] sco_connect_cfm+0x79/0x300
[bluetooth]
[ 120.766529] [<ffffffffa0094b13>]
hci_sync_conn_complete_evt.isra.90+0x343/0x400 [bluetooth]
[ 120.766529] [<ffffffffa009d447>] hci_event_packet+0x317/0xfb0
[bluetooth]
[ 120.766529] [<ffffffffa008aa68>] hci_rx_work+0x2c8/0x890
[bluetooth]
[ 120.766529] [<ffffffff81047db7>] process_one_work+0x197/0x460
[ 120.766529] [<ffffffff810489d6>] worker_thread+0x126/0x2d0
[ 120.766529] [<ffffffff8104ee4d>] kthread+0x9d/0xb0
[ 120.766529] [<ffffffff813c4294>] kernel_thread_helper+0x4/0x10
[ 120.766529]
[ 120.766529] -> #0 (&(&conn->lock)->rlock#2){+.+...}:
[ 120.766529] [<ffffffff81078a8a>] __lock_acquire+0x154a/0x1d30
[ 120.766529] [<ffffffff8107980e>] lock_acquire+0x8e/0xb0
[ 120.766529] [<ffffffff813c19e0>] _raw_spin_lock+0x40/0x80
[ 120.766529] [<ffffffffa00b7ecc>] sco_chan_del+0x4c/0x170
[bluetooth]
[ 120.766529] [<ffffffffa00b8414>] sco_conn_del+0x74/0xe0
[bluetooth]
[ 120.766529] [<ffffffffa00b88a2>] sco_disconn_cfm+0x32/0x60
[bluetooth]
[ 120.766529] [<ffffffffa0093a82>]
hci_disconn_complete_evt.isra.53+0x242/0x390 [bluetooth]
[ 120.766529] [<ffffffffa009d747>] hci_event_packet+0x617/0xfb0
[bluetooth]
[ 120.766529] [<ffffffffa008aa68>] hci_rx_work+0x2c8/0x890
[bluetooth]
[ 120.766529] [<ffffffff81047db7>] process_one_work+0x197/0x460
[ 120.766529] [<ffffffff810489d6>] worker_thread+0x126/0x2d0
[ 120.766529] [<ffffffff8104ee4d>] kthread+0x9d/0xb0
[ 120.766529] [<ffffffff813c4294>] kernel_thread_helper+0x4/0x10
[ 120.766529]
[ 120.766529] other info that might help us debug this:
[ 120.766529]
[ 120.766529] Possible unsafe locking scenario:
[ 120.766529]
[ 120.766529] CPU0 CPU1
[ 120.766529] ---- ----
[ 120.766529] lock(slock-AF_BLUETOOTH-BTPROTO_SCO);
[ 120.766529]
lock(&(&conn->lock)->rlock#2);
[ 120.766529]
lock(slock-AF_BLUETOOTH-BTPROTO_SCO);
[ 120.766529] lock(&(&conn->lock)->rlock#2);
[ 120.766529]
[ 120.766529] *** DEADLOCK ***
Signed-off-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
---
net/bluetooth/sco.c | 19 +++++++++----------
1 file changed, 9 insertions(+), 10 deletions(-)
diff --git a/net/bluetooth/sco.c b/net/bluetooth/sco.c
index cbdd313..596fdc8 100644
--- a/net/bluetooth/sco.c
+++ b/net/bluetooth/sco.c
@@ -149,6 +149,15 @@ static int sco_conn_del(struct hci_conn *hcon, int err)
sco_sock_clear_timer(sk);
sco_chan_del(sk, err);
bh_unlock_sock(sk);
+
+ sco_conn_lock(conn);
+ conn->sk = NULL;
+ sco_pi(sk)->conn = NULL;
+ sco_conn_unlock(conn);
+
+ if (conn->hcon)
+ hci_conn_put(conn->hcon);
+
sco_sock_kill(sk);
}
@@ -838,16 +847,6 @@ static void sco_chan_del(struct sock *sk, int err)
BT_DBG("sk %p, conn %p, err %d", sk, conn, err);
- if (conn) {
- sco_conn_lock(conn);
- conn->sk = NULL;
- sco_pi(sk)->conn = NULL;
- sco_conn_unlock(conn);
-
- if (conn->hcon)
- hci_conn_put(conn->hcon);
- }
-
sk->sk_state = BT_CLOSED;
sk->sk_err = err;
sk->sk_state_change(sk);
--
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