Re: [PATCH v2 0/8] Avoid L2CAP ERTM shutdown hung tasks

[Dean Jenkins <Dean_Jenkins@mentor.com>]

Hi Johan,

Please can you point to me to some details on how to use the 
l2cap-tester tool so that I can attempt to look into this issue.

Thanks,

Regards,
Dean

On 09/07/15 10:36, Johan Hedberg wrote:
> Hi,
>
> On Thu, Jul 09, 2015, Marcel Holtmann wrote:
>>> Dean Jenkins (8):
>>>   Bluetooth: L2CAP ERTM shutdown protect sk and chan
>>>   Bluetooth: Make __l2cap_wait_ack more efficient
>>>   Bluetooth: Unwind l2cap_sock_shutdown()
>>>   Bluetooth: l2cap_sock_shutdown() remove mutex_lock calls
>>>   Bluetooth: l2cap_sock_shutdown() reduce scope of chan locking
>>>   Bluetooth: Add BT_DBG to l2cap_sock_shutdown()
>>>   Bluetooth: __l2cap_wait_ack() use msecs_to_jiffies()
>>>   Bluetooth: __l2cap_wait_ack() add defensive timeout
>>>
>>> include/net/bluetooth/l2cap.h |  2 ++
>>> net/bluetooth/l2cap_sock.c    | 74 +++++++++++++++++++++++++++----------------
>>> 2 files changed, 49 insertions(+), 27 deletions(-)
>> all 8 patches have been applied to bluetooth-next tree.
> I'm getting the following now when running our l2cap-tester tool:
>
> [Jul 9 12:34] ======================================================
> [  +0.000298] [ INFO: possible circular locking dependency detected ]
> [  +0.000298] 4.1.0-rc4+ #1356 Not tainted
> [  +0.000165] -------------------------------------------------------
> [  +0.000288] l2cap-tester/10613 is trying to acquire lock:
> [  +0.000000]  (sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP){+.+...}, at: [<f942807e>] lock_sock+0xa/0xc [bluetooth]
> [  +0.000336]
>                but task is already holding lock:
> [  +0.000000]  (&chan->lock/1){+.+...}, at: [<f94283b6>] l2cap_chan_lock+0x13/0x15 [bluetooth]
> [  +0.000000]
>                which lock already depends on the new lock.
>
> [  +0.000000]
>                the existing dependency chain (in reverse order) is:
> [  +0.000000]
>                -> #1 (&chan->lock/1){+.+...}:
> [  +0.000000]        [<c1064917>] lock_acquire+0xdd/0x14f
> [  +0.000000]        [<c13ff419>] mutex_lock_nested+0x54/0x393
> [  +0.000000]        [<f94283b6>] l2cap_chan_lock+0x13/0x15 [bluetooth]
> [  +0.000000]        [<f9428ec1>] l2cap_sock_shutdown+0x28c/0x327 [bluetooth]
> [  +0.000000]        [<f942937a>] l2cap_sock_release+0x57/0xa5 [bluetooth]
> [  +0.000000]        [<c1318032>] sock_release+0x19/0x6b
> [  +0.000000]        [<c1318094>] sock_close+0x10/0x14
> [  +0.000000]        [<c10e808a>] __fput+0xd6/0x162
> [  +0.000000]        [<c10e8146>] ____fput+0xd/0xf
> [  +0.000000]        [<c1049bc8>] task_work_run+0x7e/0xa4
> [  +0.000000]        [<c1001d1e>] do_notify_resume+0x3c/0x3f
> [  +0.000000]        [<c1402730>] work_notifysig+0x29/0x31
> [  +0.000000]
>                -> #0 (sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP){+.+...}:
> [  +0.000000]        [<c1064396>] __lock_acquire+0x98c/0xbfb
> [  +0.000000]        [<c1064917>] lock_acquire+0xdd/0x14f
> [  +0.000000]        [<c131cb86>] lock_sock_nested+0x63/0x7d
> [  +0.000000]        [<f942807e>] lock_sock+0xa/0xc [bluetooth]
> [  +0.000000]        [<f9428ed9>] l2cap_sock_shutdown+0x2a4/0x327 [bluetooth]
> [  +0.000000]        [<f942937a>] l2cap_sock_release+0x57/0xa5 [bluetooth]
> [  +0.000000]        [<c1318032>] sock_release+0x19/0x6b
> [  +0.000000]        [<c1318094>] sock_close+0x10/0x14
> [  +0.000000]        [<c10e808a>] __fput+0xd6/0x162
> [  +0.000000]        [<c10e8146>] ____fput+0xd/0xf
> [  +0.000000]        [<c1049bc8>] task_work_run+0x7e/0xa4
> [  +0.000000]        [<c1001d1e>] do_notify_resume+0x3c/0x3f
> [  +0.000000]        [<c1402730>] work_notifysig+0x29/0x31
> [  +0.000000]
>                other info that might help us debug this:
>
> [  +0.000000]  Possible unsafe locking scenario:
>
> [  +0.000000]        CPU0                    CPU1
> [  +0.000000]        ----                    ----
> [  +0.000000]   lock(&chan->lock/1);
> [  +0.000000]                                lock(sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP);
> [  +0.000000]                                lock(&chan->lock/1);
> [  +0.000000]   lock(sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP);
> [  +0.000000]
>                 *** DEADLOCK ***
>
> [  +0.000000] 1 lock held by l2cap-tester/10613:
> [  +0.000000]  #0:  (&chan->lock/1){+.+...}, at: [<f94283b6>] l2cap_chan_lock+0x13/0x15 [bluetooth]
> [  +0.000000]
>                stack backtrace:
> [  +0.000000] CPU: 1 PID: 10613 Comm: l2cap-tester Not tainted 4.1.0-rc4+ #1356
> [  +0.000000] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.8.1-20150318_183358- 04/01/2014
> [  +0.000000]  00000000 00000000 f1acbde4 c13fd7f8 c1c2d760 f1acbe14 c1062c61 c15f5534
> [  +0.000000]  c15f5427 c15f53ef c15f5410 c15f53ef f1acbe48 f537f380 f537f7fc f537f380
> [  +0.000000]  f537f814 f1acbe78 c1064396 f537f7fc 00000000 00000000 c1c2ffc0 00000000
> [  +0.000000] Call Trace:
> [  +0.000000]  [<c13fd7f8>] dump_stack+0x49/0x73
> [  +0.000000]  [<c1062c61>] print_circular_bug+0x190/0x19d
> [  +0.000000]  [<c1064396>] __lock_acquire+0x98c/0xbfb
> [  +0.000000]  [<c1064917>] lock_acquire+0xdd/0x14f
> [  +0.000000]  [<f942807e>] ? lock_sock+0xa/0xc [bluetooth]
> [  +0.000000]  [<c131cb86>] lock_sock_nested+0x63/0x7d
> [  +0.000000]  [<f942807e>] ? lock_sock+0xa/0xc [bluetooth]
> [  +0.000000]  [<f942807e>] lock_sock+0xa/0xc [bluetooth]
> [  +0.000000]  [<f9428ed9>] l2cap_sock_shutdown+0x2a4/0x327 [bluetooth]
> [  +0.000000]  [<f9401112>] ? bt_sock_unlink+0x16/0x54 [bluetooth]
> [  +0.000000]  [<c1402276>] ? _raw_write_unlock+0x2c/0x3e
> [  +0.000000]  [<f942937a>] l2cap_sock_release+0x57/0xa5 [bluetooth]
> [  +0.000000]  [<f942937a>] ? l2cap_sock_release+0x57/0xa5 [bluetooth]
> [  +0.000000]  [<c1318032>] sock_release+0x19/0x6b
> [  +0.000000]  [<c1318032>] ? sock_release+0x19/0x6b
> [  +0.000000]  [<c1318094>] sock_close+0x10/0x14
> [  +0.000000]  [<c10e808a>] __fput+0xd6/0x162
> [  +0.000000]  [<c10e8146>] ____fput+0xd/0xf
> [  +0.000000]  [<c1049bc8>] task_work_run+0x7e/0xa4
> [  +0.000000]  [<c1001d1e>] do_notify_resume+0x3c/0x3f
> [  +0.000000]  [<c1402730>] work_notifysig+0x29/0x31
>
> Johan


-- 
Dean Jenkins
Embedded Software Engineer
Linux Transportation Solutions
Mentor Embedded Software Division
Mentor Graphics (UK) Ltd.