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* BUG: scsi/qla2xxx: BUG_ON(blk_queued_rq(req) is triggered in blk_finish_request
@ 2018-05-23  3:55
  2018-05-24  1:50 `
  0 siblings, 1 reply; 3+ messages in thread
From: @ 2018-05-23  3:55 UTC (permalink / raw)
  To: qla2xxx-upstream, himanshu.madhani, jthumshirn
  Cc: linux-scsi, linux-kernel, jejb, Martin K. Petersen, Junxiao Bi

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
  -> 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                                                         
                                                      -> 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 ?


^ permalink raw reply	[flat|nested] 3+ messages in thread

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