Re: iscsi_trx going into D state

Robert LeBlanc
2016-12-21T23:39:55Z

I hit a new backtrace today, hopefully it adds something.

# cat /proc/19659/stack
[<ffffffff815304d1>] iscsit_stop_session+0x1b1/0x1c0
[<ffffffff81521c62>] iscsi_check_for_session_reinstatement+0x1e2/0x270
[<ffffffff81524660>] iscsi_target_check_for_existing_instances+0x30/0x40
[<ffffffff815247a8>] iscsi_target_do_login+0x138/0x630
[<ffffffff815259be>] iscsi_target_start_negotiation+0x4e/0xa0
[<ffffffff8152355e>] __iscsi_target_login_thread+0x83e/0xf20
[<ffffffff81523c64>] iscsi_target_login_thread+0x24/0x30
[<ffffffff810a3059>] kthread+0xd9/0xf0
[<ffffffff817732d5>] ret_from_fork+0x25/0x30
[<ffffffffffffffff>] 0xffffffffffffffff

# cat /proc/21342/stack
[<ffffffffa0292b10>] __ib_drain_sq+0x190/0x1c0 [ib_core]
[<ffffffffa0292b65>] ib_drain_sq+0x25/0x30 [ib_core]
[<ffffffffa0292d72>] ib_drain_qp+0x12/0x30 [ib_core]
[<ffffffffa062c5ff>] isert_wait_conn+0x5f/0x2d0 [ib_isert]
[<ffffffff815309b7>] iscsit_close_connection+0x157/0x860
[<ffffffff8151f10b>] iscsit_take_action_for_connection_exit+0x7b/0xf0
[<ffffffff81530265>] iscsi_target_rx_thread+0x95/0xa0
[<ffffffff810a3059>] kthread+0xd9/0xf0
[<ffffffff817732d5>] ret_from_fork+0x25/0x30
[<ffffffffffffffff>] 0xffffffffffffffff

# ps aux | grep iscsi | grep D
root 19659 0.0 0.0 0 0 ? D 16:12 0:00 [iscsi_np]
root 21342 0.0 0.0 0 0 ? D 16:29 0:00 [iscsi_trx]
----------------
Robert LeBlanc
PGP Fingerprint 79A2 9CA4 6CC4 45DD A904 C70E E654 3BB2 FA62 B9F1

On Thu, Dec 15, 2016 at 1:38 PM, Robert LeBlanc <robert-4JaGZRWAfWbajFs6igw21g@public.gmane.org> wrote:
> Nicholas,
>
> I've found that the kernels I used were not able to be inspected using
> crash and I could not build the debug info for them. So I built a new
> 4.9 kernel and verified that I could inspect the crash. It is located
> at [1].
>
> [1] http://mirrors.betterservers.com/trace/crash2.tar.xz
> ----------------
> Robert LeBlanc
> PGP Fingerprint 79A2 9CA4 6CC4 45DD A904 C70E E654 3BB2 FA62 B9F1
>
>
> On Mon, Dec 12, 2016 at 4:57 PM, Robert LeBlanc <robert-4JaGZRWAfWbajFs6igw21g@public.gmane.org> wrote:
>> Nicholas,
>>
>> After lots of set backs and having to give up trying to get kernel
>> dumps on our "production" systems, I've been able to work out the
>> issues we had with kdump and replicate the issue on my dev boxes. I
>> have dumps from 4.4.30 and 4.9-rc8 (makedumpfile would not dump, so it
>> is a straight copy of /proc/vmcore from the crash kernel). In each
>> crash directory, I put a details.txt file that has the process IDs
>> that were having problems and a brief description of the set-up at the
>> time. This was mostly replicated by starting fio and pulling the
>> Infiniband cable until fio gave up. This hardware also has Mellanox
>> ConnectX4-LX cards and I also replicated the issue over RoCE using 4.9
>> since it has the drivers in-box. Please let me know if you need more
>> info, I can test much faster now. The cores/kernels/modules are
>> located at [1].
>>
>> [1] http://mirrors.betterservers.com/trace/crash.tar.xz
>>
>> Thanks,
>> Robert
>> ----------------
>> Robert LeBlanc
>> PGP Fingerprint 79A2 9CA4 6CC4 45DD A904 C70E E654 3BB2 FA62 B9F1
>>
>>
>> On Fri, Nov 4, 2016 at 3:57 PM, Robert LeBlanc <robert-4JaGZRWAfWbajFs6igw21g@public.gmane.org> wrote:
>>> We hit this yesterday, this time it was on the tx thread (the other
>>> ones before seem to be on the rx thread). We weren't able to get a
>>> kernel dump on this. We'll try to get one next time.
>>>
>>> # ps axuw | grep "D.*iscs[i]"
>>> root 12383 0.0 0.0 0 0 ? D Nov03 0:04 [iscsi_np]
>>> root 23016 0.0 0.0 0 0 ? D Nov03 0:00 [iscsi_ttx]
>>> root 23018 0.0 0.0 0 0 ? D Nov03 0:00 [iscsi_ttx]
>>> # cat /proc/12383/stack
>>> [<ffffffff814f24af>] iscsit_stop_session+0x19f/0x1d0
>>> [<ffffffff814e3c66>] iscsi_check_for_session_reinstatement+0x1e6/0x270
>>> [<ffffffff814e6620>] iscsi_target_check_for_existing_instances+0x30/0x40
>>> [<ffffffff814e6770>] iscsi_target_do_login+0x140/0x640
>>> [<ffffffff814e7b0c>] iscsi_target_start_negotiation+0x1c/0xb0
>>> [<ffffffff814e585b>] iscsi_target_login_thread+0xa9b/0xfc0
>>> [<ffffffff8109d7c8>] kthread+0xd8/0xf0
>>> [<ffffffff81721a8f>] ret_from_fork+0x3f/0x70
>>> [<ffffffffffffffff>] 0xffffffffffffffff
>>> # cat /proc/23016/stack
>>> [<ffffffff814ce0d9>] target_wait_for_sess_cmds+0x49/0x1a0
>>> [<ffffffffa058b92b>] isert_wait_conn+0x1ab/0x2f0 [ib_isert]
>>> [<ffffffff814f2642>] iscsit_close_connection+0x162/0x870
>>> [<ffffffff814e110f>] iscsit_take_action_for_connection_exit+0x7f/0x100
>>> [<ffffffff814f122a>] iscsi_target_tx_thread+0x1aa/0x1d0
>>> [<ffffffff8109d7c8>] kthread+0xd8/0xf0
>>> [<ffffffff81721a8f>] ret_from_fork+0x3f/0x70
>>> [<ffffffffffffffff>] 0xffffffffffffffff
>>> # cat /proc/23018/stack
>>> [<ffffffff814ce0d9>] target_wait_for_sess_cmds+0x49/0x1a0
>>> [<ffffffffa058b92b>] isert_wait_conn+0x1ab/0x2f0 [ib_isert]
>>> [<ffffffff814f2642>] iscsit_close_connection+0x162/0x870
>>> [<ffffffff814e110f>] iscsit_take_action_for_connection_exit+0x7f/0x100
>>> [<ffffffff814f122a>] iscsi_target_tx_thread+0x1aa/0x1d0
>>> [<ffffffff8109d7c8>] kthread+0xd8/0xf0
>>> [<ffffffff81721a8f>] ret_from_fork+0x3f/0x70
>>> [<ffffffffffffffff>] 0xffffffffffffffff
>>>
>>> From dmesg:
>>> [ 394.476332] INFO: rcu_sched self-detected stall on CPU
>>> [ 394.476334] 20-...: (23976 ticks this GP)
>>> idle=edd/140000000000001/0 softirq=292/292 fqs=18788
>>> [ 394.476336] (t=24003 jiffies g=3146 c=3145 q=0)
>>> [ 394.476337] Task dump for CPU 20:
>>> [ 394.476338] kworker/u68:2 R running task 0 12906 2 0x00000008
>>> [ 394.476345] Workqueue: isert_comp_wq isert_cq_work [ib_isert]
>>> [ 394.476346] ffff883f2fe38000 00000000f805705e ffff883f7fd03da8
>>> ffffffff810ac8ff
>>> [ 394.476347] 0000000000000014 ffffffff81adb680 ffff883f7fd03dc0
>>> ffffffff810af239
>>> [ 394.476348] 0000000000000015 ffff883f7fd03df0 ffffffff810e1cd0
>>> ffff883f7fd17b80
>>> [ 394.476348] Call Trace:
>>> [ 394.476354] <IRQ> [<ffffffff810ac8ff>] sched_show_task+0xaf/0x110
>>> [ 394.476355] [<ffffffff810af239>] dump_cpu_task+0x39/0x40
>>> [ 394.476357] [<ffffffff810e1cd0>] rcu_dump_cpu_stacks+0x80/0xb0
>>> [ 394.476359] [<ffffffff810e6100>] rcu_check_callbacks+0x540/0x820
>>> [ 394.476360] [<ffffffff810afe11>] ? account_system_time+0x81/0x110
>>> [ 394.476363] [<ffffffff810faa60>] ? tick_sched_do_timer+0x50/0x50
>>> [ 394.476364] [<ffffffff810eb599>] update_process_times+0x39/0x60
>>> [ 394.476365] [<ffffffff810fa815>] tick_sched_handle.isra.17+0x25/0x60
>>> [ 394.476366] [<ffffffff810faa9d>] tick_sched_timer+0x3d/0x70
>>> [ 394.476368] [<ffffffff810ec182>] __hrtimer_run_queues+0x102/0x290
>>> [ 394.476369] [<ffffffff810ec668>] hrtimer_interrupt+0xa8/0x1a0
>>> [ 394.476372] [<ffffffff81052c65>] local_apic_timer_interrupt+0x35/0x60
>>> [ 394.476374] [<ffffffff8172423d>] smp_apic_timer_interrupt+0x3d/0x50
>>> [ 394.476376] [<ffffffff817224f7>] apic_timer_interrupt+0x87/0x90
>>> [ 394.476379] <EOI> [<ffffffff810d71be>] ? console_unlock+0x41e/0x4e0
>>> [ 394.476380] [<ffffffff810d757c>] vprintk_emit+0x2fc/0x500
>>> [ 394.476382] [<ffffffff810d78ff>] vprintk_default+0x1f/0x30
>>> [ 394.476384] [<ffffffff81174dde>] printk+0x5d/0x74
>>> [ 394.476388] [<ffffffff814bce21>] transport_lookup_cmd_lun+0x1d1/0x200
>>> [ 394.476390] [<ffffffff814ee8c0>] iscsit_setup_scsi_cmd+0x230/0x540
>>> [ 394.476392] [<ffffffffa058dbf3>] isert_rx_do_work+0x3f3/0x7f0 [ib_isert]
>>> [ 394.476394] [<ffffffffa058e174>] isert_cq_work+0x184/0x770 [ib_isert]
>>> [ 394.476396] [<ffffffff8109740f>] process_one_work+0x14f/0x400
>>> [ 394.476397] [<ffffffff81097c84>] worker_thread+0x114/0x470
>>> [ 394.476398] [<ffffffff8171d32a>] ? __schedule+0x34a/0x7f0
>>> [ 394.476399] [<ffffffff81097b70>] ? rescuer_thread+0x310/0x310
>>> [ 394.476400] [<ffffffff8109d7c8>] kthread+0xd8/0xf0
>>> [ 394.476402] [<ffffffff8109d6f0>] ? kthread_park+0x60/0x60
>>> [ 394.476403] [<ffffffff81721a8f>] ret_from_fork+0x3f/0x70
>>> [ 394.476404] [<ffffffff8109d6f0>] ? kthread_park+0x60/0x60
>>> [ 405.716632] Unexpected ret: -104 send data 360
>>> [ 405.721711] tx_data returned -32, expecting 360.
>>> ----------------
>>> Robert LeBlanc
>>> PGP Fingerprint 79A2 9CA4 6CC4 45DD A904 C70E E654 3BB2 FA62 B9F1
>>>
>>>
>>> On Mon, Oct 31, 2016 at 10:34 AM, Robert LeBlanc <robert-4JaGZRWAfWbajFs6igw21g@public.gmane.org> wrote:
>>>> Nicholas,
>>>>
>>>> Thanks for following up on this. We have been chasing other bugs in
>>>> our provisioning and as such has reduced our load on the boxes. We are
>>>> hoping to get that all straightened out this week and do some more
>>>> testing. So far we have not had any iSCSI in D state since the patch,
>>>> be we haven't been able to test it well either. We will keep you
>>>> updated.
>>>>
>>>> Thank you,
>>>> Robert LeBlanc
>>>> ----------------
>>>> Robert LeBlanc
>>>> PGP Fingerprint 79A2 9CA4 6CC4 45DD A904 C70E E654 3BB2 FA62 B9F1
>>>>
>>>>
>>>> On Sat, Oct 29, 2016 at 4:29 PM, Nicholas A. Bellinger
>>>> <nab-IzHhD5pYlfBP7FQvKIMDCQ@public.gmane.org> wrote:
>>>>> Hi Robert,
>>>>>
>>>>> On Wed, 2016-10-19 at 10:41 -0600, Robert LeBlanc wrote:
>>>>>> Nicholas,
>>>>>>
>>>>>> I didn't have high hopes for the patch because we were not seeing
>>>>>> TMR_ABORT_TASK (or 'abort') in dmesg or /var/log/messages, but it
>>>>>> seemed to help regardless. Our clients finally OOMed from the hung
>>>>>> sessions, so we are having to reboot them and we will do some more
>>>>>> testing. We haven't put the updated kernel on our clients yet. Our
>>>>>> clients have iSCSI root disks so I'm not sure if we can get a vmcore
>>>>>> on those, but we will do what we can to get you a vmcore from the
>>>>>> target if it happens again.
>>>>>>
>>>>>
>>>>> Just checking in to see if you've observed further issues with
>>>>> iser-target ports, and/or able to generate a crashdump with v4.4.y..?
>>>>>
>>>>>> As far as our configuration: It is a superMicro box with 6 SAMSUNG
>>>>>> MZ7LM3T8HCJM-00005 SSDs. Two are for root and four are in mdadm
>>>>>> RAID-10 for exporting via iSCSI/iSER. We have ZFS on top of the
>>>>>> RAID-10 for checksum and snapshots only and we export ZVols to the
>>>>>> clients (one or more per VM on the client). We do not persist the
>>>>>> export info (targetcli saveconfig), but regenerate it from scripts.
>>>>>> The client receives two or more of these exports and puts them in a
>>>>>> RAID-1 device. The exports are served by iSER one one port and also by
>>>>>> normal iSCSI on a different port for compatibility, but not normally
>>>>>> used. If you need more info about the config, please let me know. It
>>>>>> was kind of a vague request so I'm not sure what exactly is important
>>>>>> to you.
>>>>>
>>>>> Thanks for the extra details of your hardware + user-space
>>>>> configuration.
>>>>>
>>>>>> Thanks for helping us with this,
>>>>>> Robert LeBlanc
>>>>>>
>>>>>> When we have problems, we usually see this in the logs:
>>>>>> Oct 17 08:57:50 prv-0-12-sanstack kernel: iSCSI Login timeout on
>>>>>> Network Portal 0.0.0.0:3260
>>>>>> Oct 17 08:57:50 prv-0-12-sanstack kernel: Unexpected ret: -104 send data 48
>>>>>> Oct 17 08:57:50 prv-0-12-sanstack kernel: tx_data returned -32, expecting 48.
>>>>>> Oct 17 08:57:50 prv-0-12-sanstack kernel: iSCSI Login negotiation failed.
>>>>>>
>>>>>> I found some backtraces in the logs, not sure if this is helpful, this
>>>>>> is before your patch (your patch booted at Oct 18 10:36:59):
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: INFO: rcu_sched
>>>>>> self-detected stall on CPU
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: #0115-...: (41725 ticks this
>>>>>> GP) idle=b59/140000000000001/0 softirq=535/535 fqs=30992
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: #011 (t=42006 jiffies g=1550
>>>>>> c=1549 q=0)
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: Task dump for CPU 5:
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: kworker/u68:2 R running
>>>>>> task 0 17967 2 0x00000008
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: Workqueue: isert_comp_wq
>>>>>> isert_cq_work [ib_isert]
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: ffff883f4c0dca80
>>>>>> 00000000af8ca7a4 ffff883f7fb43da8 ffffffff810ac83f
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: 0000000000000005
>>>>>> ffffffff81adb680 ffff883f7fb43dc0 ffffffff810af179
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: 0000000000000006
>>>>>> ffff883f7fb43df0 ffffffff810e1c10 ffff883f7fb57b80
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: Call Trace:
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: <IRQ> [<ffffffff810ac83f>]
>>>>>> sched_show_task+0xaf/0x110
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffff810af179>]
>>>>>> dump_cpu_task+0x39/0x40
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffff810e1c10>]
>>>>>> rcu_dump_cpu_stacks+0x80/0xb0
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffff810e6040>]
>>>>>> rcu_check_callbacks+0x540/0x820
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffff810afd51>] ?
>>>>>> account_system_time+0x81/0x110
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffff810fa9a0>] ?
>>>>>> tick_sched_do_timer+0x50/0x50
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffff810eb4d9>]
>>>>>> update_process_times+0x39/0x60
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffff810fa755>]
>>>>>> tick_sched_handle.isra.17+0x25/0x60
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffff810fa9dd>]
>>>>>> tick_sched_timer+0x3d/0x70
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffff810ec0c2>]
>>>>>> __hrtimer_run_queues+0x102/0x290
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffff810ec5a8>]
>>>>>> hrtimer_interrupt+0xa8/0x1a0
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffff81052c65>]
>>>>>> local_apic_timer_interrupt+0x35/0x60
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffff8172343d>]
>>>>>> smp_apic_timer_interrupt+0x3d/0x50
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffff817216f7>]
>>>>>> apic_timer_interrupt+0x87/0x90
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: <EOI> [<ffffffff810d70fe>]
>>>>>> ? console_unlock+0x41e/0x4e0
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffff810d74bc>]
>>>>>> vprintk_emit+0x2fc/0x500
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffff810d783f>]
>>>>>> vprintk_default+0x1f/0x30
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffff81174c2a>] printk+0x5d/0x74
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffff814bc351>]
>>>>>> transport_lookup_cmd_lun+0x1d1/0x200
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffff814edcf0>]
>>>>>> iscsit_setup_scsi_cmd+0x230/0x540
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffffa0890bf3>]
>>>>>> isert_rx_do_work+0x3f3/0x7f0 [ib_isert]
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffffa0891174>]
>>>>>> isert_cq_work+0x184/0x770 [ib_isert]
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffff8109734f>]
>>>>>> process_one_work+0x14f/0x400
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffff81097bc4>]
>>>>>> worker_thread+0x114/0x470
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffff8171c55a>] ?
>>>>>> __schedule+0x34a/0x7f0
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffff81097ab0>] ?
>>>>>> rescuer_thread+0x310/0x310
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffff8109d708>] kthread+0xd8/0xf0
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffff8109d630>] ?
>>>>>> kthread_park+0x60/0x60
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffff81720c8f>]
>>>>>> ret_from_fork+0x3f/0x70
>>>>>> Oct 17 15:43:12 prv-0-12-sanstack kernel: [<ffffffff8109d630>] ?
>>>>>> kthread_park+0x60/0x60
>>>>>>
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: INFO: rcu_sched
>>>>>> self-detected stall on CPU
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: #01128-...: (5999 ticks this
>>>>>> GP) idle=2f9/140000000000001/0 softirq=457/457 fqs=4830
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: #011 (t=6000 jiffies g=3546
>>>>>> c=3545 q=0)
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: Task dump for CPU 28:
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: iscsi_np R running
>>>>>> task 0 16597 2 0x0000000c
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: ffff887f40350000
>>>>>> 00000000b98a67bb ffff887f7f503da8 ffffffff810ac8ff
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: 000000000000001c
>>>>>> ffffffff81adb680 ffff887f7f503dc0 ffffffff810af239
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: 000000000000001d
>>>>>> ffff887f7f503df0 ffffffff810e1cd0 ffff887f7f517b80
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: Call Trace:
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: <IRQ> [<ffffffff810ac8ff>]
>>>>>> sched_show_task+0xaf/0x110
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: [<ffffffff810af239>]
>>>>>> dump_cpu_task+0x39/0x40
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: [<ffffffff810e1cd0>]
>>>>>> rcu_dump_cpu_stacks+0x80/0xb0
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: [<ffffffff810e6100>]
>>>>>> rcu_check_callbacks+0x540/0x820
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: [<ffffffff810afe11>] ?
>>>>>> account_system_time+0x81/0x110
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: [<ffffffff810faa60>] ?
>>>>>> tick_sched_do_timer+0x50/0x50
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: [<ffffffff810eb599>]
>>>>>> update_process_times+0x39/0x60
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: [<ffffffff810fa815>]
>>>>>> tick_sched_handle.isra.17+0x25/0x60
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: [<ffffffff810faa9d>]
>>>>>> tick_sched_timer+0x3d/0x70
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: [<ffffffff810ec182>]
>>>>>> __hrtimer_run_queues+0x102/0x290
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: [<ffffffff810ec668>]
>>>>>> hrtimer_interrupt+0xa8/0x1a0
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: [<ffffffff81052c65>]
>>>>>> local_apic_timer_interrupt+0x35/0x60
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: [<ffffffff81723cbd>]
>>>>>> smp_apic_timer_interrupt+0x3d/0x50
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: [<ffffffff81721f77>]
>>>>>> apic_timer_interrupt+0x87/0x90
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: <EOI> [<ffffffff810d71be>]
>>>>>> ? console_unlock+0x41e/0x4e0
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: [<ffffffff810d757c>]
>>>>>> vprintk_emit+0x2fc/0x500
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: [<ffffffff810d78ff>]
>>>>>> vprintk_default+0x1f/0x30
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: [<ffffffff81174dde>] printk+0x5d/0x74
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: [<ffffffff814e71ad>]
>>>>>> iscsi_target_locate_portal+0x62d/0x6f0
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: [<ffffffff814e5100>]
>>>>>> iscsi_target_login_thread+0x6f0/0xfc0
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: [<ffffffff814e4a10>] ?
>>>>>> iscsi_target_login_sess_out+0x250/0x250
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: [<ffffffff8109d7c8>] kthread+0xd8/0xf0
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: [<ffffffff8109d6f0>] ?
>>>>>> kthread_park+0x60/0x60
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: [<ffffffff8172150f>]
>>>>>> ret_from_fork+0x3f/0x70
>>>>>> Oct 17 16:34:03 prv-0-12-sanstack kernel: [<ffffffff8109d6f0>] ?
>>>>>> kthread_park+0x60/0x60
>>>>>>
>>>>>> I don't think this one is related, but it happened a couple of times:
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: INFO: rcu_sched
>>>>>> self-detected stall on CPU
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: #01119-...: (5999 ticks this
>>>>>> GP) idle=727/140000000000001/0 softirq=1346/1346 fqs=4990
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: #011 (t=6000 jiffies g=4295
>>>>>> c=4294 q=0)
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: Task dump for CPU 19:
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: kworker/19:1 R running
>>>>>> task 0 301 2 0x00000008
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: Workqueue:
>>>>>> events_power_efficient fb_flashcursor
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: ffff883f6009ca80
>>>>>> 00000000010a7cdd ffff883f7fcc3da8 ffffffff810ac8ff
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: 0000000000000013
>>>>>> ffffffff81adb680 ffff883f7fcc3dc0 ffffffff810af239
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: 0000000000000014
>>>>>> ffff883f7fcc3df0 ffffffff810e1cd0 ffff883f7fcd7b80
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: Call Trace:
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: <IRQ> [<ffffffff810ac8ff>]
>>>>>> sched_show_task+0xaf/0x110
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: [<ffffffff810af239>]
>>>>>> dump_cpu_task+0x39/0x40
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: [<ffffffff810e1cd0>]
>>>>>> rcu_dump_cpu_stacks+0x80/0xb0
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: [<ffffffff810e6100>]
>>>>>> rcu_check_callbacks+0x540/0x820
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: [<ffffffff810afe11>] ?
>>>>>> account_system_time+0x81/0x110
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: [<ffffffff810faa60>] ?
>>>>>> tick_sched_do_timer+0x50/0x50
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: [<ffffffff810eb599>]
>>>>>> update_process_times+0x39/0x60
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: [<ffffffff810fa815>]
>>>>>> tick_sched_handle.isra.17+0x25/0x60
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: [<ffffffff810faa9d>]
>>>>>> tick_sched_timer+0x3d/0x70
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: [<ffffffff810ec182>]
>>>>>> __hrtimer_run_queues+0x102/0x290
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: [<ffffffff810ec668>]
>>>>>> hrtimer_interrupt+0xa8/0x1a0
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: [<ffffffff81052c65>]
>>>>>> local_apic_timer_interrupt+0x35/0x60
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: [<ffffffff81723cbd>]
>>>>>> smp_apic_timer_interrupt+0x3d/0x50
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: [<ffffffff81721f77>]
>>>>>> apic_timer_interrupt+0x87/0x90
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: <EOI> [<ffffffff810d71be>]
>>>>>> ? console_unlock+0x41e/0x4e0
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: [<ffffffff813866ad>]
>>>>>> fb_flashcursor+0x5d/0x140
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: [<ffffffff8138bc00>] ?
>>>>>> bit_clear+0x110/0x110
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: [<ffffffff8109740f>]
>>>>>> process_one_work+0x14f/0x400
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: [<ffffffff81097c84>]
>>>>>> worker_thread+0x114/0x470
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: [<ffffffff8171cdda>] ?
>>>>>> __schedule+0x34a/0x7f0
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: [<ffffffff81097b70>] ?
>>>>>> rescuer_thread+0x310/0x310
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: [<ffffffff8109d7c8>] kthread+0xd8/0xf0
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: [<ffffffff8109d6f0>] ?
>>>>>> kthread_park+0x60/0x60
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: [<ffffffff8172150f>]
>>>>>> ret_from_fork+0x3f/0x70
>>>>>> Oct 17 11:46:52 prv-0-12-sanstack kernel: [<ffffffff8109d6f0>] ?
>>>>>> kthread_park+0x60/0x60
>>>>>
>>>>> RCU self-detected schedule stalls typically mean some code is
>>>>> monopolizing execution on a specific CPU for an extended period of time
>>>>> (eg: endless loop), preventing normal RCU grace-period callbacks from
>>>>> running in a timely manner.
>>>>>
>>>>> It's hard to tell without more log context and/or crashdump what was
>>>>> going on here.
>>>>>