Re: Close connection aborting an out-of-order cmd will hang

[Jirong Feng <jirong.feng@easystack.cn>]

[root@node-6 ~]# uname -r

4.18.0-147.5.1.es8_24.aarch64


Our linux distro is forked from rhel 8.1, whose kernel version is 
kernel-4.18.0-147.5.1.el8_1.


[root@node-6 ~]# modinfo iscsi_target_mod
filename: 
/lib/modules/4.18.0-147.5.1.es8_24.aarch64/extra/target_core/iscsi/iscsi_target_mod.ko
license:        GPL
author:         nab@Linux-iSCSI.org
version:        4.1.x
description:    iSCSI-Target Driver for mainline target infrastructure
rhelversion:    8.1
srcversion:     C986C35ED15D27ACAFD2927
depends:        target_core_mod
name:           iscsi_target_mod
vermagic:       4.18.0-147.5.1.es8_24.aarch64 SMP mod_unload modversions 
aarch64


Regards,

Jirong Feng


在 2023/7/19 17:59, Maurizio Lombardi 写道:
> Hello,
>
> út 18. 7. 2023 v 8:52 odesílatel Jirong Feng <jirong.feng@easystack.cn> napsal:
>> Hi,
>>
>> I recently encountered a hanging issue as follow:
> Can you please provide the kernel version?
>
> Thanks,
> Maurizio
>
>> [root@node-6 ~]# ps -aux | grep ' D '
>> root      8648  0.4  0.0      0     0 ?        D    Jul12  21:04 [iscsi_np]
>> root     17572  0.0  0.0      0     0 ?        D    Jul12   0:09
>> [kworker/7:3+events]
>> root     56555  0.0  0.0 216576  1536 pts/1    S+   14:57   0:00 grep
>> --color=auto  D
>> root     59853  0.0  0.0      0     0 ?        D    Jul12   0:04 [iscsi_trx]
>>
>> the call stack:
>> kworker:
>> PID: 17572  TASK: ffff862470df0e00  CPU: 7   COMMAND: "kworker/7:3"
>>    #0 [ffff0000528afab0] __switch_to at ffff4a49c69e74b8
>>    #1 [ffff0000528afad0] __schedule at ffff4a49c72b60f4
>>    #2 [ffff0000528afb60] schedule at ffff4a49c72b6754
>>    #3 [ffff0000528afb70] schedule_timeout at ffff4a49c72ba980
>>    #4 [ffff0000528afc30] wait_for_common at ffff4a49c72b7504
>>    #5 [ffff0000528afcb0] wait_for_completion at ffff4a49c72b7594
>>    #6 [ffff0000528afcd0] target_put_cmd_and_wait at ffff4a49a3dad38c
>> [target_core_mod]
>>    #7 [ffff0000528afd30] core_tmr_abort_task at ffff4a49a3da55c8
>> [target_core_mod]
>>    #8 [ffff0000528afd80] target_tmr_work at ffff4a49a3daa1c8
>> [target_core_mod]
>>    #9 [ffff0000528afdb0] process_one_work at ffff4a49c6a603c0
>> #10 [ffff0000528afe00] worker_thread at ffff4a49c6a60640
>> #11 [ffff0000528afe60] kthread at ffff4a49c6a67474
>>
>> iscsi_trx:
>> PID: 59853  TASK: ffff8624fe0b5200  CPU: 7   COMMAND: "iscsi_trx"
>>    #0 [ffff000095f6fa50] __switch_to at ffff4a49c69e74b8
>>    #1 [ffff000095f6fa70] __schedule at ffff4a49c72b60f4
>>    #2 [ffff000095f6fb00] schedule at ffff4a49c72b6754
>>    #3 [ffff000095f6fb10] schedule_timeout at ffff4a49c72ba870
>>    #4 [ffff000095f6fbd0] wait_for_common at ffff4a49c72b7504
>>    #5 [ffff000095f6fc50] wait_for_completion_timeout at ffff4a49c72b75d0
>>    #6 [ffff000095f6fc70] __transport_wait_for_tasks at ffff4a49a3da9c28
>> [target_core_mod]
>>    #7 [ffff000095f6fcb0] transport_generic_free_cmd at ffff4a49a3da9dd0
>> [target_core_mod]
>>    #8 [ffff000095f6fd20] iscsit_free_cmd at ffff4a49a3fc4464
>> [iscsi_target_mod]
>>    #9 [ffff000095f6fd50] iscsit_close_connection at ffff4a49a3fccf48
>> [iscsi_target_mod]
>> #10 [ffff000095f6fdf0] iscsit_take_action_for_connection_exit at
>> ffff4a49a3fb7614 [iscsi_target_mod]
>> #11 [ffff000095f6fe20] iscsi_target_rx_thread at ffff4a49a3fcc064
>> [iscsi_target_mod]
>> #12 [ffff000095f6fe60] kthread at ffff4a49c6a67474
>>
>> inspect the aborting cmd in kworker:
>> crash> struct iscsi_cmd FFFFA62592F4B400
>> struct iscsi_cmd {
>>     dataout_timer_flags = (unknown: 0),
>>     dataout_timeout_retries = 0 '\000',
>>     error_recovery_count = 0 '\000',
>>     deferred_i_state = ISTATE_NEW_CMD,
>>     i_state = ISTATE_DEFERRED_CMD,
>>     immediate_cmd = 0 '\000',
>>     immediate_data = 0 '\000',
>>     iscsi_opcode = 1 '\001',
>>     iscsi_response = 0 '\000',
>>     logout_reason = 0 '\000',
>>     logout_response = 0 '\000',
>>     maxcmdsn_inc = 0 '\000',
>>     unsolicited_data = 0 '\000',
>>     reject_reason = 0 '\000',
>>     logout_cid = 0,
>>     cmd_flags = ICF_OOO_CMDSN,
>>     init_task_tag = 2415919152,
>>     targ_xfer_tag = 205,
>>     cmd_sn = 2860352639,
>>     exp_stat_sn = 2502541166,
>>     stat_sn = 0,
>>     data_sn = 0,
>> ...
>>
>> so this is an out-of-order cmd. In my conclusion, trx is waiting for
>> kworker to abort the cmd,  while kworker is waiting for someone to
>> complete the cmd, and that is never going to happen, hence the hanging.
>>
>> Could someone please help me to confirm the case?
>>
>> Regards,
>> Jirong Feng
>>
>>
>