On 09/29/2016 07:01 PM, Bart Van Assche wrote:
> On 09/28/2016 10:46 PM, Hannes Reinecke wrote:
>> On 09/29/2016 01:45 AM, Bart Van Assche wrote:
>>> The code at the end of alua_rtpg_work() is as follows:
>>>
>>> scsi_device_put(sdev);
>>> kref_put(&pg->kref, release_port_group);
>>>
>>> Make sure that all code that queues the work item associated
>>> with alua_rtpg_work() holds both references.
>>>
>>> Signed-off-by: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
>>> Cc: Hannes Reinecke <hare@xxxxxxxx>
>>> Cc: <stable@xxxxxxxxxxxxxxx>
>>> ---
>>> drivers/scsi/device_handler/scsi_dh_alua.c | 1 +
>>> 1 file changed, 1 insertion(+)
>>>
>>> diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c
>>> b/drivers/scsi/device_handler/scsi_dh_alua.c
>>> index 752b5c9..f7099e2 100644
>>> --- a/drivers/scsi/device_handler/scsi_dh_alua.c
>>> +++ b/drivers/scsi/device_handler/scsi_dh_alua.c
>>> @@ -889,6 +889,7 @@ static void alua_rtpg_queue(struct
>>> alua_port_group *pg,
>>> /* Do not queue if the worker is already running */
>>> if (!(pg->flags & ALUA_PG_RUNNING)) {
>>> kref_get(&pg->kref);
>>> + scsi_device_get(sdev);
>>> start_queue = 1;
>>> }
>>> }
>>>
>> Nack.
>>
>> The scsi device reference tracks ->rtpg_sdev, not the queue item.
>> So we only need to take the scsi device reference if we're assigning a
>> new value to ->rtpg_sdev, which we are not.
>
> Hello Hannes,
>
> If queue_delayed_work() returns 0 that means that a call to
> alua_rtpg_work() has already been scheduled. alua_rtpg_work() will drop
> the reference on pg->rtpg_sdev. Are you sure that alua_rtpg_queue()
> should call scsi_device_put(sdev) in that case?
>
Ah, now I see what you mean.
However, your patch is still incorrect; when doing so we'll end up with
a duplicate reference if the call to queue_delayed_work() succeeds.
I'll be sending an updated patch.
Cheers,
Hannes
--
Dr. Hannes Reinecke zSeries & Storage
hare@xxxxxxx +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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