Re: [PATCH 1/2] scsi: core: scsi_device_online() return false if state is SDEV_CANCEL

[Wenchao Hao]

On 2023/9/22 23:23, Bart Van Assche wrote:
> On 9/22/23 02:36, Wenchao Hao wrote:
> > SDEV_CANCEL is set when removing device and scsi_device_online() should
> > return false if sdev_state is SDEV_CANCEL.
> >
> > IO hang would be caused if return true when state is SDEV_CANCEL with
> > following order:
> >
> > T1:                        T2:scsi_error_handler
> > __scsi_remove_device()
> >    scsi_device_set_state(sdev, SDEV_CANCEL)
> >                            scsi_eh_flush_done_q()
> >                         if (scsi_device_online(sdev))
> >                           scsi_queue_insert(scmd,...)
> >
> > The command added by scsi_queue_insert() would never be handled any
> > more.
>
> Why not? I think the blk_mq_destroy_queue() call in __scsi_remove_device() will cause it to fail.
>
> Thanks,
>
> Bart.

Sorry, I did not describe in detail, the __scsi_remove_device() would be blocked
in blk_mq_freeze_queue_wait() to wait all block requests finished, so
blk_mq_destroy_queue() would not be called, and the task which try to remove
scsi_device would be hung.