Re: [dm-devel] [PATCH 2/3] scsi_dh: Remove the workqueue used foractivate

[Mike Christie <michaelc cs wisc edu>]

Chandra Seetharaman wrote:
> On Wed, 2009-05-06 at 22:32 -0500, Mike Christie wrote:
> > Chandra Seetharaman wrote:
> > > Since scsi_dh_activate() has become an asynchronous function,
> > > we do not need a workqueue for submitting scsi_dh_activate().
> > >
> > > This patch just removes the workqueue that submits scsi_dh_activate().
> > Before this is merged, we need to convert the other device handlers to 
> > use blk_execute_rq_nowait or use their own workqueue_struct right?
>
> If we want those modules also behave async, then yes.
>
> But, this set of 3 patches would work fine as I made the relevant
> changes to those modules so that they work properly.
>  

What was the point of the workqueue?

I think if you merged the patch and left the other modules as is you 
would hit a problem where the multipathd work queue struct thread is 
busy waiting on activate commands when it should be routing IO to paths 
that do not need a activate.