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
blk_execute_rq（...）
atomic_dec(&sdev->nr_admin_pending);
wake_up_all(&sdev->admin_wq);
Thanks
Jianchao
