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SubjectRe: BUG: scsi/qla2xxx: BUG_ON(blk_queued_rq(req) is triggered in blk_finish_request
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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
>
>

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