Re: [PATCH V3 11/17] SCSI: track pending admin commands

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On Fri, Sep 14, 2018 at 11:40 AM jianchao.wang
<jianchao.w.wang@xxxxxxxxxx> wrote:
>
> Hi Ming
>
> On 09/13/2018 08:15 PM, Ming Lei wrote:
> >  EXPORT_SYMBOL(__scsi_execute);
> > @@ -3246,6 +3251,7 @@ static int scsi_internal_device_block(struct scsi_device *sdev)
> >               else
> >                       scsi_wait_for_queuecommand(sdev);
> >       }
> > +     wait_event(sdev->admin_wq, !atomic_read(&sdev->nr_admin_pending));
> >       mutex_unlock(&sdev->state_mutex);
> >
> >       return err;
> ...
> > diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
> > index 3aee9464a7bf..8bcb7ecc0c06 100644
> > --- a/drivers/scsi/scsi_sysfs.c
> > +++ b/drivers/scsi/scsi_sysfs.c
> > @@ -1393,6 +1393,7 @@ void __scsi_remove_device(struct scsi_device *sdev)
> >
> >       blk_cleanup_queue(sdev->request_queue);
> >       cancel_work_sync(&sdev->requeue_work);
> > +     wait_event(sdev->admin_wq, !atomic_read(&sdev->nr_admin_pending))
>
> This nr_admin_pending could drain the ongoing scsi_request_fn/scsi_queue_rq,
> but I'm afraid it cannot stop new ones coming in, such as the ones that have passed
> the sdev state checking and have not crossed the atomic_inc(&sdev->nr_admin_pending).
>

The counter of .nr_admin_pending is introduced for draining queued
admin requests to this scsi device.

Actually new requests have been prevented from entering scsi_queue_rq(),
please see the two callers of wait_event(sdev->admin_wq,
!atomic_read(&sdev->nr_admin_pending)).

Thanks,
Ming Lei



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