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SubjectRe: scsi/qla2xxx: BUG_ON(blk_queued_rq(req) is triggered in blk_finish_request
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Hi Himanshu

I think the core issue here is:
We should invoke scsi_done for the aborted request in qla2x00_sp_compl.
The requeue or the other operation on the aborted request should be done by the SCSI mid-layer.

Would you please give some comment here ?

Thanks in advance
Jianchao

On 06/05/2018 09:11 AM, jianchao.wang wrote:
> Hi Himanshu
>
> Would you please give some comment here?
>
> Thanks
> Jianchao
>
> On 05/30/2018 11:28 AM, jianchao.wang wrote:
>> Hi Himanshu
>>
>> Thanks for your kindly response.
>>
>> On 05/30/2018 01:44 AM, Madhani, Himanshu wrote:
>>> Thanks for the information. I was out for couple days. Still working through my emails.
>>>
>>> Without core dump shared with us, things become hard to debug. We'll take a look at this data.
>>>
>>> Also, if you have any reproducer test case, Can you share that with us so that we can try to trigger It internally and see if we have better luck debugging that.
>>
>> This issue occurred in customer's environment twice till now, there is no reproduce steps.
>>
>> If you have time, would you please look at our analysis to see whether it is reasonable ?
>> The kernel is not newest, but there should be the same issue in mainline with scsi + block legacy
>> The key point here is:
>> when the aborted command returns in irq context, it will invoke scsi_done, then blk_complete_request.
>> however, the scsi recovery context could clear the ATOM_COMPLETE and requeue the request before irq
>> context get it.
>>
>> Thanks
>> Jianchao
>>
>>>
>>> On 5/28/18, 6:11 PM, "jianchao.wang" <jianchao.w.wang@oracle.com> wrote:
>>>
>>> Hi Himanshu
>>>
>>> do you need any other information ?
>>>
>>> Thanks
>>> Jianchao
>>>
>>> On 05/25/2018 02:48 PM, jianchao.wang wrote:
>>> > Hi Himanshu
>>> >
>>> > I'm afraid I cannot provide you the vmcore file, it is from our customer.
>>> > If any information needed in the vmcore, I could provide with you.
>>> >
>>> > In this scene, there are two contexts:
>>> > 1. the irq context, scsi_done() from qla2x00_sp_compl()
>>> > 2. the kworker context, scmd_eh_abort_handler which invokes the
>>> > qla2xxx_eh_abort()
>>> >
>>> > Let's see the irq context.
>>> > scsi_done() will invoke the blk_complete_request().
>>> > In common case, the REQ_ATOM_COMPLETE should have been set by
>>> > blk_rq_check_expired() when the request was confirmed timeout. So
>>> > __blk_complete_request() will not be invoked.
>>> >
>>> > On the other hand, in the kworker context, scmd_eh_abort_handler() will do some
>>> > other things on this aborted request.
>>> >
>>> > rtn = scsi_try_to_abort_cmd(sdev->host->hostt, scmd);
>>> > if (rtn == SUCCESS) {
>>> > set_host_byte(scmd, DID_TIME_OUT)
>>> > if (scsi_host_eh_past_deadline(sdev->host)) {
>>> > >>>>
>>> > } else if (!scsi_noretry_cmd(scmd) &&
>>> > (++scmd->retries <= scmd->allowed)) {
>>> > scsi_queue_insert(scmd, SCSI_MLQUEUE_EH_RETRY)
>>> > }>>>>
>>> >>>>>
>>> > }
>>> > The host type of the result will set to DID_TIME_OUT. scsi_noretry_cmd() will
>>> > return false and scsi_queue_insert() will be invoked, finally the
>>> > blk_requeue_request().
>>> >
>>> > blk_requeue_request() will clear the REQ_ATOM_COMPLETE and queue the request on
>>> > request_queue->queue_head.
>>> >
>>> > There could be a race between these two contexts:
>>> > what if the blk_clear_rq_complete() in kworker context is invoked before the
>>> > blk_mark_rq_complete() in irq context ?
>>> >
>>> > BLK_SOFTIRQ will be raised by __blk_complete_request() in irq context. Then the
>>> > scsi_softirq_done() will be invoked. At the moment, the request has been
>>> > requeued by kworker context and scsi_cmnd->result is set 0. On the cpu of the
>>> > irq context, the blk_finish_request() will be invoked finally, and panic comes
>>> > up due to BUG_ON(blk_queued_rq(req)
>>> >
>>> > Here is the dmesg log.
>>> > [4937745.180213] qla2xxx [0000:92:00.1]-801c:4: Abort command issued nexus=4:5:5 -- 1 2002.
>>> > [4937745.180655] qla2xxx [0000:92:00.1]-801c:4: Abort command issued nexus=4:4:73 -- 0 2002.
>>> > [4937745.181059] qla2xxx [0000:92:00.1]-801c:4: Abort command issued nexus=4:5:5 -- 1 2002.
>>> > [4937745.181514] qla2xxx [0000:92:00.1]-801c:4: Abort command issued nexus=4:4:73 -- 0 2002.
>>> > [4937745.181636] ------------[ cut here ]------------
>>> > [4937745.181900] kernel BUG at block/blk-core.c:2601!
>>> > [4937745.182095] qla2xxx [0000:92:00.1]-801c:4: Abort command issued nexus=4:5:5 -- 1 2002.
>>> > [4937745.182338] qla2xxx [0000:92:00.1]-801c:4: Abort command issued nexus=4:4:73 -- 1 2002.
>>> > [4937745.183046] qla2xxx [0000:92:00.1]-801c:4: Abort command issued nexus=4:5:5 -- 1 2002.
>>> > [4937745.183213] qla2xxx [0000:92:00.1]-801c:4: Abort command issued nexus=4:4:73 -- 1 2002.
>>> > [4937745.183844] qla2xxx [0000:92:00.1]-801c:4: Abort command issued nexus=4:5:5 -- 1 2002.
>>> > [4937745.184038] qla2xxx [0000:92:00.1]-801c:4: Abort command issued nexus=4:4:73 -- 1 2002.
>>> > [4937745.184919] invalid opcode: 0000 [#1] SMP
>>> > [4937745.185173] Modules linked in: ...
>>> > [4937745.188237] CPU: 18 PID: 0 Comm: swapper/18 Not tainted 4.1.12-61.1.9.el6uek.x86_64 #2
>>> > [4937745.188691] Hardware name: Oracle Corporation SUN BLADE X4-2B /BD,ASSY,PCB,X4-2B , BIOS 28010200 01/16/2014
>>> > [4937745.189157] task: ffff880227fa9c00 ti: ffff880227fc0000 task.ti: ffff880227fc0000
>>> > [4937745.189607] RIP: e030:[<ffffffff812ed130>] [<ffffffff812ed130>] blk_finish_request+0xd0/0xe0
>>> > [4937745.190104] RSP: e02b:ffff88022d483d78 EFLAGS: 00010083
>>> > [4937745.190339] RAX: 0000000000000280 RBX: ffff8801c4508730 RCX: 0000000000000280
>>> > [4937745.190791] RDX: 0000000000008b5a RSI: 0000000000000000 RDI: ffff8801c4508730
>>> > [4937745.191246] RBP: ffff88022d483d88 R08: 0000000000000000 R09: 0000000000004000
>>> > [4937745.191694] R10: 000000000000000b R11: 0000000000007ffe R12: 0000000000000000
>>> > [4937745.192153] R13: ffff88022374d000 R14: ffff880184cb88c0 R15: ffff8800536ccc90
>>> > [4937745.197930] FS: 0000000000000000(0000) GS:ffff88022d480000(0000) knlGS:ffff88022d480000
>>> > [4937745.198389] CS: e033 DS: 002b ES: 002b CR0: 0000000080050033
>>> > [4937745.198627] CR2: 00000000016e1f18 CR3: 000000010caed000 CR4: 0000000000042660
>>> > [4937745.199080] Stack:
>>> > [4937745.199309] ffff8801c4508730 0000000000000000 ffff88022d483dd8 ffffffff814ac82f
>>> > [4937745.199790] ffff88022d483da8 0000000000000280 ffff88022d483dd8 ffff880184cb88c0
>>> > [4937745.200290] ffff8801c4508730 0000000000000000 0000000000000000 0000000000000000
>>> > [4937745.200745] Call Trace:
>>> > [4937745.200968] <IRQ>
>>> > [4937745.200986] [<ffffffff814ac82f>] scsi_end_request+0x11f/0x1e0
>>> > [4937745.201422] [<ffffffff814accfc>] scsi_io_completion+0xac/0x500
>>> > [4937745.201651] [<ffffffff814a3bb0>] scsi_finish_command+0xf0/0x150
>>> > [4937745.201875] [<ffffffff814ad2ba>] scsi_softirq_done+0x14a/0x160
>>> > [4937745.202103] [<ffffffff812f3c66>] blk_done_softirq+0x86/0xa0
>>> > [4937745.202333] [<ffffffff8108879a>] __do_softirq+0x10a/0x350
>>> > [4937745.202558] [<ffffffff81088b55>] irq_exit+0x125/0x130
>>> > [4937745.202787] [<ffffffff813e5a89>] xen_evtchn_do_upcall+0x39/0x50
>>> > [4937745.203020] [<ffffffff816cce5e>] xen_do_hypervisor_callback+0x1e/0x40
>>> > [4937745.203247] <EOI>
>>> > [4937745.203263] [<ffffffff810013aa>] ? xen_hypercall_sched_op+0xa/0x20
>>> > [4937745.203703] [<ffffffff810013aa>] ? xen_hypercall_sched_op+0xa/0x20
>>> > [4937745.203930] [<ffffffff8100baf0>] ? xen_safe_halt+0x10/0x20
>>> > [4937745.204160] [<ffffffff81022abe>] ? default_idle+0x1e/0x100
>>> > [4937745.204387] [<ffffffff8102210f>] ? arch_cpu_idle+0xf/0x20
>>> > [4937745.204614] [<ffffffff810c8f25>] ? cpuidle_idle_call+0x135/0x1e0
>>> > [4937745.204841] [<ffffffff810c91c5>] ? cpu_idle_loop+0x1f5/0x220
>>> > [4937745.205070] [<ffffffff810c920b>] ? cpu_startup_entry+0x1b/0x70
>>> > [4937745.205294] [<ffffffff810c924f>] ? cpu_startup_entry+0x5f/0x70
>>> > [4937745.205524] [<ffffffff81013a5a>] ? cpu_bringup_and_idle+0x2a/0x40
>>> > [4937745.205749] Code: 89 de e8 a4 14 00 00 e9 6b ff ff ff 83 7b 48 01 0f 85
>>> > 78 ff ff ff 48 8b 7b 30 48 81 c7 98 01 00 00 e8 75 6b ea ff e9 63 ff ff ff
>>> > <0f> 0b eb fe 66 66 66 2e 0f 1f 84 00 00 00 00 00 55 48 89 e5 48
>>> > [4937745.206811] RIP [<ffffffff812ed130>] blk_finish_request+0xd0/0xe0
>>> > [4937745.207046] RSP <ffff88022d483d78>
>>> > [4937745.207687] ---[ end trace 0b43a57bdab9464f ]---
>>> > [4937745.207693] ------------[ cut here ]------------
>>> >
>>> > On 05/25/2018 02:30 PM, Madhani, Himanshu wrote:
>>> >> Hi Jianchao,
>>> >>
>>> >> Do you have any debug logs collected for us to look at this in details.
>>> >>
>>> >> Can you provide me crash/vmlinux/modules for details analysis.
>>> >>
>>> >> Thanks,
>>> >> himanshu
>>> >>
>>> >> On 5/24/18, 6:49 AM, "Madhani, Himanshu" <Himanshu.Madhani@cavium.com> wrote:
>>> >>
>>> >>
>>> >> > On May 24, 2018, at 2:09 AM, jianchao.wang <jianchao.w.wang@oracle.com> wrote:
>>> >> >
>>> >> > Hi Himanshu
>>> >> >
>>> >> > Thanks god get response from your side finally :)
>>> >> > I get qla2xxx-upstream@qlogic.com from the maintainer information of driver/scsi/qla2xxx
>>> >> > Looks like it should be modified.
>>> >> >
>>> >> Sorry for delay. I do try to respond quickly to any emails received on that ID as well.
>>> >>
>>> >> We’ll keep it for now and I’ll look into updating it, if needed.
>>> >>
>>> >> > Thanks
>>> >> > Jianchao
>>> >> >
>>> >> > On 05/24/2018 12:21 PM, Madhani, Himanshu wrote:
>>> >> >> Hi,
>>> >> >>
>>> >> >> Yes. We'll look at this issue.
>>> >> >>
>>> >> >> Thanks,
>>> >> >> Himanshu
>>> >> >>
>>> >> >>> -----Original Message-----
>>> >> >>> From: jianchao.wang [mailto:jianchao.w.wang@oracle.com]
>>> >> >>> Sent: Wednesday, May 23, 2018 6:51 PM
>>> >> >>> To: Dept-Eng QLA2xxx Upstream <qla2xxx-upstream@cavium.com>; Madhani,
>>> >> >>> Himanshu <Himanshu.Madhani@cavium.com>; jthumshirn@suse.de
>>> >> >>> Cc: linux-scsi@vger.kernel.org; linux-kernel@vger.kernel.org;
>>> >> >>> jejb@linux.vnet.ibm.com; Martin K. Petersen <martin.petersen@oracle.com>;
>>> >> >>> Junxiao Bi <junxiao.bi@oracle.com>
>>> >> >>> Subject: Re: BUG: scsi/qla2xxx: BUG_ON(blk_queued_rq(req) is triggered in
>>> >> >>> blk_finish_request
>>> >> >>>
>>> >> >>> Would anyone please take a look at this ?
>>> >> >>>
>>> >> >>> Thanks in advance
>>> >> >>> Jianchao
>>> >> >>>
>>> >> >>> On 05/23/2018 11:55 AM, jianchao.wang wrote:
>>> >> >>>>
>>> >> >>>>
>>> >> >>>> Hi all
>>> >> >>>>
>>> >> >>>> Our customer met a panic triggered by BUG_ON in blk_finish_request.
>>> >> >>>>> From the dmesg log, the BUG_ON was triggered after command abort
>>> >> >>> occurred many times.
>>> >> >>>> There is a race condition in the following scenario.
>>> >> >>>>
>>> >> >>>> cpu A cpu B
>>> >> >>>> kworker interrupt
>>> >> >>>>
>>> >> >>>> scmd_eh_abort_handler()
>>> >> >>>> -> scsi_try_to_abort_cmd()
>>> >> >>>> -> qla2xxx_eh_abort()
>>> >> >>>> -> qla2x00_eh_wait_on_command() qla2x00_status_entry()
>>> >> >>>> -> qla2x00_sp_compl()
>>> >> >>>> -> qla2x00_sp_free_dma()
>>> >> >>>> -> scsi_queue_insert()
>>> >> >>>> -> __scsi_queue_insert()
>>> >> >>>> -> blk_requeue_request()
>>> >> >>>> -> blk_clear_rq_complete()
>>> >> >>>> -> scsi_done
>>> >> >>>> -> blk_complete_request
>>> >> >>>> -> blk_mark_rq_complete
>>> >> >>>> -> elv_requeue_request() -> __blk_complete_request()
>>> >> >>>> -> __elv_add_request()
>>> >> >>>> // req will be queued here
>>> >> >>>> BLK_SOFTIRQ
>>> >> >>>> scsi_softirq_done()
>>> >> >>>> -> scsi_finish_command()
>>> >> >>>> -> scsi_io_completion()
>>> >> >>>> -> scsi_end_request()
>>> >> >>>> -> blk_finish_request() //
>>> >> >>> BUG_ON(blk_queued_rq(req)) !!!
>>> >> >>>>
>>> >> >>>> The issue will not be triggered most of time, because the request is marked as
>>> >> >>> complete by timeout path.
>>> >> >>>> So the scsi_done from qla2x00_sp_compl does nothing.
>>> >> >>>> But as the scenario above, if the complete state has been cleaned by
>>> >> >>> blk_requeue_request, we will get
>>> >> >>>> the request both requeued and completed, and then
>>> >> >>> BUG_ON(blk_queued_rq(req)) in blk_finish_request comes up.
>>> >> >>>>
>>> >> >>>> Is there any solution for this in qla2xxx driver side ?
>>> >> >>>>
>>> >> >>>> Thanks
>>> >> >>>> Jianchao
>>> >> >>>>
>>> >> >>>>
>>> >>
>>> >> Thanks,
>>> >> - Himanshu
>>> >>
>>> >>
>>> >>
>>> >
>>>
>>>
>

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