[ 1003.760488] PPP generic driver version 2.4.2
[ 1008.042682] Bluetooth: TIOCGSERIAL is not supported
[ 1008.850769] Bluetooth: TIOCGSERIAL is not supported
[ 1042.449682] PPP BSD Compression module registered
[ 1042.458694] PPP Deflate Compression module registered
[ 1128.563091] 
[ 1128.563097] ======================================================
[ 1128.563099] [ INFO: possible circular locking dependency detected ]
[ 1128.563103] 3.7.0 #195 Not tainted
[ 1128.563105] -------------------------------------------------------
[ 1128.563107] kworker/1:1/31 is trying to acquire lock:
[ 1128.563109]  (&tty->legacy_mutex){+.+.+.}, at: [<c150f286>] tty_lock_nested+0x36/0x80
[ 1128.563123] 
[ 1128.563123] but task is already holding lock:
[ 1128.563125]  ((&tty->hangup_work)){+.+...}, at: [<c1052983>] process_one_work+0x123/0x4d0
[ 1128.563135] 
[ 1128.563135] which lock already depends on the new lock.
[ 1128.563135] 
[ 1128.563138] 
[ 1128.563138] the existing dependency chain (in reverse order) is:
[ 1128.563140] 
[ 1128.563140] -> #2 ((&tty->hangup_work)){+.+...}:
[ 1128.563145]        [<c1085809>] lock_acquire+0x79/0xf0
[ 1128.563151]        [<c1053168>] flush_work+0x48/0x250
[ 1128.563155]        [<c1294a56>] tty_ldisc_flush_works+0x16/0x30
[ 1128.563160]        [<c1295941>] tty_ldisc_release+0x21/0x70
[ 1128.563164]        [<c128ee7c>] tty_release+0x37c/0x4a0
[ 1128.563170]        [<c11175cc>] __fput+0xcc/0x1f0
[ 1128.563176]        [<c11176fd>] ____fput+0xd/0x10
[ 1128.563179]        [<c1056eb9>] task_work_run+0x89/0xa0
[ 1128.563184]        [<c1002b11>] do_notify_resume+0x51/0x80
[ 1128.563189]        [<c150f578>] work_notifysig+0x29/0x31
[ 1128.563193] 
[ 1128.563193] -> #1 (&tty->legacy_mutex/1){+.+...}:
[ 1128.563199]        [<c1085809>] lock_acquire+0x79/0xf0
[ 1128.563203]        [<c150c1fa>] mutex_lock_nested+0x4a/0x2f0
[ 1128.563208]        [<c150f286>] tty_lock_nested+0x36/0x80
[ 1128.563212]        [<c150f319>] tty_lock_pair+0x29/0x70
[ 1128.563216]        [<c128ec30>] tty_release+0x130/0x4a0
[ 1128.563220]        [<c11175cc>] __fput+0xcc/0x1f0
[ 1128.563224]        [<c11176fd>] ____fput+0xd/0x10
[ 1128.563227]        [<c1056eb9>] task_work_run+0x89/0xa0
[ 1128.563231]        [<c1002b11>] do_notify_resume+0x51/0x80
[ 1128.563235]        [<c150f578>] work_notifysig+0x29/0x31
[ 1128.563239] 
[ 1128.563239] -> #0 (&tty->legacy_mutex){+.+.+.}:
[ 1128.563243]        [<c10852ae>] __lock_acquire+0x165e/0x1710
[ 1128.563248]        [<c1085809>] lock_acquire+0x79/0xf0
[ 1128.563252]        [<c150c1fa>] mutex_lock_nested+0x4a/0x2f0
[ 1128.563255]        [<c150f286>] tty_lock_nested+0x36/0x80
[ 1128.563259]        [<c150f2df>] tty_lock+0xf/0x20
[ 1128.563263]        [<c128d904>] __tty_hangup+0x54/0x430
[ 1128.563267]        [<c128dcf2>] do_tty_hangup+0x12/0x20
[ 1128.563272]        [<c1052a02>] process_one_work+0x1a2/0x4d0
[ 1128.563275]        [<c1054509>] worker_thread+0x119/0x3b0
[ 1128.563279]        [<c105a1ff>] kthread+0x9f/0xb0
[ 1128.563283]        [<c150fc37>] ret_from_kernel_thread+0x1b/0x28
[ 1128.563287] 
[ 1128.563287] other info that might help us debug this:
[ 1128.563287] 
[ 1128.563290] Chain exists of:
[ 1128.563290]   &tty->legacy_mutex --> &tty->legacy_mutex/1 --> (&tty->hangup_work)
[ 1128.563290] 
[ 1128.563297]  Possible unsafe locking scenario:
[ 1128.563297] 
[ 1128.563299]        CPU0                    CPU1
[ 1128.563301]        ----                    ----
[ 1128.563302]   lock((&tty->hangup_work));
[ 1128.563305]                                lock(&tty->legacy_mutex/1);
[ 1128.563309]                                lock((&tty->hangup_work));
[ 1128.563312]   lock(&tty->legacy_mutex);
[ 1128.563315] 
[ 1128.563315]  *** DEADLOCK ***
[ 1128.563315] 
[ 1128.563319] 2 locks held by kworker/1:1/31:
[ 1128.563320]  #0:  (events){.+.+.+}, at: [<c1052983>] process_one_work+0x123/0x4d0
[ 1128.563328]  #1:  ((&tty->hangup_work)){+.+...}, at: [<c1052983>] process_one_work+0x123/0x4d0
[ 1128.563335] 
[ 1128.563335] stack backtrace:
[ 1128.563339] Pid: 31, comm: kworker/1:1 Not tainted 3.7.0 #195
[ 1128.563341] Call Trace:
[ 1128.563348]  [<c1506992>] print_circular_bug+0x1af/0x1b9
[ 1128.563352]  [<c10852ae>] __lock_acquire+0x165e/0x1710
[ 1128.563358]  [<c1085809>] lock_acquire+0x79/0xf0
[ 1128.563362]  [<c150f286>] ? tty_lock_nested+0x36/0x80
[ 1128.563366]  [<c150c1fa>] mutex_lock_nested+0x4a/0x2f0
[ 1128.563370]  [<c150f286>] ? tty_lock_nested+0x36/0x80
[ 1128.563375]  [<c128d8d2>] ? __tty_hangup+0x22/0x430
[ 1128.563379]  [<c150f286>] tty_lock_nested+0x36/0x80
[ 1128.563383]  [<c150f2df>] tty_lock+0xf/0x20
[ 1128.563388]  [<c128d904>] __tty_hangup+0x54/0x430
[ 1128.563391]  [<c1052983>] ? process_one_work+0x123/0x4d0
[ 1128.563396]  [<c128dcf2>] do_tty_hangup+0x12/0x20
[ 1128.563400]  [<c1052a02>] process_one_work+0x1a2/0x4d0
[ 1128.563403]  [<c1052983>] ? process_one_work+0x123/0x4d0
[ 1128.563407]  [<c10545ae>] ? worker_thread+0x1be/0x3b0
[ 1128.563411]  [<c128dce0>] ? __tty_hangup+0x430/0x430
[ 1128.563415]  [<c1054509>] worker_thread+0x119/0x3b0
[ 1128.563419]  [<c10543f0>] ? __next_gcwq_cpu+0x60/0x60
[ 1128.563424]  [<c105a1ff>] kthread+0x9f/0xb0
[ 1128.563428]  [<c150fc37>] ret_from_kernel_thread+0x1b/0x28
[ 1128.563433]  [<c105a160>] ? kthread_create_on_node+0xe0/0xe0