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From: "jianchao.wang" <jianchao.w.wang@oracle.com>
To: qla2xxx-upstream@qlogic.com, himanshu.madhani@cavium.com,
	jthumshirn@suse.de
Cc: linux-scsi@vger.kernel.org,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"jejb@linux.vnet.ibm.com" <jejb@linux.vnet.ibm.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	Junxiao Bi <junxiao.bi@oracle.com>
Subject: BUG: scsi/qla2xxx: BUG_ON(blk_queued_rq(req) is triggered in blk_finish_request
Date: Wed, 23 May 2018 11:55:29 +0800	[thread overview]
Message-ID: <5eb1eeaa-b148-7b90-eee4-e365ead49a5b@oracle.com> (raw)



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

             reply	other threads:[~2018-05-23  3:55 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-23  3:55 jianchao.wang [this message]
2018-05-24  1:50 ` jianchao.wang
     [not found]   ` <SN4PR0701MB363286637D0317358D61ECBFF56A0@SN4PR0701MB3632.namprd07.prod.outlook.com>
2018-05-24  9:09     ` jianchao.wang

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