Re: [PATCH 08/17] scsi_dh_alua: Make stpg synchronous

Hannes Reinecke
2015-05-11T13:59:36Z

On 05/11/2015 03:50 PM, Christoph Hellwig wrote:
> On Mon, May 11, 2015 at 11:59:16AM +0200, Hannes Reinecke wrote:
>> This is just an intermediate step, before the entire thing moves off
>> to a workqueue and becomes asynchronous again.
>> It's not meant to be as a standalone patch; I've just split it off
>> for easier review.
>
> It actually made the review a bit harder. Also I don't really undertand
> what the benfit of running a synchronous STPG in a workqueue is over
> running it asynchronously.
>
Because STPG might fail, at which point we need to re-run RTPG to
figure out the current status.
But that might clash with a scheduled RTPG from another task.
_And_ issuing RTPG while STPG is active is pointless, too, as
the information is pretty much guaranteed to be incorrect.

Hence the use of a workqueue to serialize RTPG and STPG against each
other.

Cheers,

Hannes
--
Dr. Hannes Reinecke zSeries & Storage
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