Commits
Andre Guedes committed a51cd2be864
Bluetooth: Fix potential deadlock
We don't need to use the _sync variant in hci_conn_hold and
hci_conn_put to cancel conn->disc_work delayed work. This way
we avoid potential deadlocks like this one reported by lockdep.
======================================================
[ INFO: possible circular locking dependency detected ]
3.2.0+ #1 Not tainted
-------------------------------------------------------
kworker/u:1/17 is trying to acquire lock:
(&hdev->lock){+.+.+.}, at: [<ffffffffa0041155>] hci_conn_timeout+0x62/0x158 [bluetooth]
but task is already holding lock:
((&(&conn->disc_work)->work)){+.+...}, at: [<ffffffff81035751>] process_one_work+0x11a/0x2bf
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 ((&(&conn->disc_work)->work)){+.+...}:
[<ffffffff81057444>] lock_acquire+0x8a/0xa7
[<ffffffff81034ed1>] wait_on_work+0x3d/0xaa
[<ffffffff81035b54>] __cancel_work_timer+0xac/0xef
[<ffffffff81035ba4>] cancel_delayed_work_sync+0xd/0xf
[<ffffffffa00554b0>] smp_chan_create+0xde/0xe6 [bluetooth]
[<ffffffffa0056160>] smp_conn_security+0xa3/0x12d [bluetooth]
[<ffffffffa0053640>] l2cap_connect_cfm+0x237/0x2e8 [bluetooth]
[<ffffffffa004239c>] hci_proto_connect_cfm+0x2d/0x6f [bluetooth]
[<ffffffffa0046ea5>] hci_event_packet+0x29d1/0x2d60 [bluetooth]
[<ffffffffa003dde3>] hci_rx_work+0xd0/0x2e1 [bluetooth]
[<ffffffff810357af>] process_one_work+0x178/0x2bf
[<ffffffff81036178>] worker_thread+0xce/0x152
[<ffffffff81039a03>] kthread+0x95/0x9d
[<ffffffff812e7754>] kernel_thread_helper+0x4/0x10
-> #1 (slock-AF_BLUETOOTH-BTPROTO_L2CAP){+.+...}:
[<ffffffff81057444>] lock_acquire+0x8a/0xa7
[<ffffffff812e553a>] _raw_spin_lock_bh+0x36/0x6a
[<ffffffff81244d56>] lock_sock_nested+0x24/0x7f
[<ffffffffa004d96f>] lock_sock+0xb/0xd [bluetooth]
[<ffffffffa0052906>] l2cap_chan_connect+0xa9/0x26f [bluetooth]
[<ffffffffa00545f8>] l2cap_sock_connect+0xb3/0xff [bluetooth]
[<ffffffff81243b48>] sys_connect+0x69/0x8a
[<ffffffff812e6579>] system_call_fastpath+0x16/0x1b
-> #0 (&hdev->lock){+.+.+.}:
[<ffffffff81056d06>] __lock_acquire+0xa80/0xd74
[<ffffffff81057444>] lock_acquire+0x8a/0xa7
[<ffffffff812e3870>] __mutex_lock_common+0x48/0x38e
[<ffffffff812e3c75>] mutex_lock_nested+0x2a/0x31
[<ffffffffa0041155>] hci_conn_timeout+0x62/0x158 [bluetooth]
[<ffffffff810357af>] process_one_work+0x178/0x2bf
[<ffffffff81036178>] worker_thread+0xce/0x152
[<ffffffff81039a03>] kthread+0x95/0x9d
[<ffffffff812e7754>] kernel_thread_helper+0x4/0x10
other info that might help us debug this:
Chain exists of:
&hdev->lock --> slock-AF_BLUETOOTH-BTPROTO_L2CAP --> (&(&conn->disc_work)->work)
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock((&(&conn->disc_work)->work));
lock(slock-AF_BLUETOOTH-BTPROTO_L2CAP);
lock((&(&conn->disc_work)->work));
lock(&hdev->lock);
*** DEADLOCK ***
2 locks held by kworker/u:1/17:
#0: (hdev->name){.+.+.+}, at: [<ffffffff81035751>] process_one_work+0x11a/0x2bf
#1: ((&(&conn->disc_work)->work)){+.+...}, at: [<ffffffff81035751>] process_one_work+0x11a/0x2bf
stack backtrace:
Pid: 17, comm: kworker/u:1 Not tainted 3.2.0+ #1
Call Trace:
[<ffffffff812e06c6>] print_circular_bug+0x1f8/0x209
[<ffffffff81056d06>] __lock_acquire+0xa80/0xd74
[<ffffffff81021ef2>] ? arch_local_irq_restore+0x6/0xd
[<ffffffff81022bc7>] ? vprintk+0x3f9/0x41e
[<ffffffff81057444>] lock_acquire+0x8a/0xa7
[<ffffffffa0041155>] ? hci_conn_timeout+0x62/0x158 [bluetooth]
[<ffffffff812e3870>] __mutex_lock_common+0x48/0x38e
[<ffffffffa0041155>] ? hci_conn_timeout+0x62/0x158 [bluetooth]
[<ffffffff81190fd6>] ? __dynamic_pr_debug+0x6d/0x6f
[<ffffffffa0041155>] ? hci_conn_timeout+0x62/0x158 [bluetooth]
[<ffffffff8105320f>] ? trace_hardirqs_off+0xd/0xf
[<ffffffff812e3c75>] mutex_lock_nested+0x2a/0x31
[<ffffffffa0041155>] hci_conn_timeout+0x62/0x158 [bluetooth]
[<ffffffff810357af>] process_one_work+0x178/0x2bf
[<ffffffff81035751>] ? process_one_work+0x11a/0x2bf
[<ffffffff81055af3>] ? lock_acquired+0x1d0/0x1df
[<ffffffffa00410f3>] ? hci_acl_disconn+0x65/0x65 [bluetooth]
[<ffffffff81036178>] worker_thread+0xce/0x152
[<ffffffff810407ed>] ? finish_task_switch+0x45/0xc5
[<ffffffff810360aa>] ? manage_workers.isra.25+0x16a/0x16a
[<ffffffff81039a03>] kthread+0x95/0x9d
[<ffffffff812e7754>] kernel_thread_helper+0x4/0x10
[<ffffffff812e5db4>] ? retint_restore_args+0x13/0x13
[<ffffffff8103996e>] ? __init_kthread_worker+0x55/0x55
[<ffffffff812e7750>] ? gs_change+0x13/0x13
Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@openbossa.org>
Reviewed-by: Ulisses Furquim <ulisses@profusion.mobi>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>