On 09/18/2018 03:39 PM, Ming Lei wrote: > On Tue, Sep 18, 2018 at 09:22:32AM +0800, jianchao.wang wrote: >> Hi Ming >> >> On 09/17/2018 07:35 PM, Ming Lei wrote: >>> On Mon, Sep 17, 2018 at 10:46:34AM +0800, jianchao.wang wrote: >>>> Hi Ming >>>> >>>> On 09/14/2018 07:33 PM, Ming Lei wrote: >>>>> 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)). >>>>> >>>> For example >>>> >>>> _scsi_execute >>>> ... >>>> scsi_internal_device_block >>>> scsi_internal_device_block_nowait >>>> blk_mq_quiesce_queue >>>> wait_event(sdev->admin_wq, !atomic_read(&sdev->nr_admin_pending)) >>>> &sdev->nr_admin_pending; >>>> >>>> blk_execute_rq（...） >>>> >>>> atomic_dec(&sdev->nr_admin_pending); >>>> wake_up_all(&sdev->admin_wq); >>>> >>>> Or do you mean the scsi_queue_rq -> scsi_prep_state_check could gate out of ? >>> >>> I got it, then this issue can be fixed simply by moving atomic_inc/dec(&sdev->nr_admin_pending) >>> and related wake_up_all(&sdev->admin_wq) into scsi_admin_queue_rq(). >>> >> >> I don't think so. It is a similar scenario. >> >> I guess a state checking is needed after atomic_inc(&sdev->nr_admin_pending), like: >> >> _scsi_execute >> ... >> scsi_internal_device_block >> scsi_internal_device_block_nowait >> blk_mq_quiesce_queue >> wait_event(sdev->admin_wq, !atomic_read(&sdev->nr_admin_pending)) >> atomic_inc(&sdev->nr_admin_pending); >> if state checking fails >> goto done > > The check will be done in scsi_admin_queue_rq(). > >> >> blk_execute_rq（...） >> >> atomic_dec(&sdev->nr_admin_pending); >> wake_up_all(&sdev->admin_wq); > > I guess you may misunderstand the purpose of .nr_admin_pending, which is > for draining requests to .queue_rq(). So it is enough to just move the > inc/dec of .nr_admin_pending into scsi_admin_queue_rq(), right? Yes. But I just think of how to assign with queue quiesce. The existence of per-host adminq seems to break it. Thanks Jianchao
