On Wed, 2016-11-09 at 08:18 -0500, Jeff Layton wrote:
> On Tue, 2016-11-08 at 20:27 -0500, J. Bruce Fields wrote:
> >
> > On Tue, Nov 08, 2016 at 05:52:21PM -0500, Tejun Heo wrote:
> > >
> > >
> > > Hello, Bruce.
> > >
> > > On Tue, Nov 08, 2016 at 04:39:11PM -0500, J. Bruce Fields wrote:
> > > >
> > > >
> > > > Apologies, just cleaning out old mail and finding some I should
> > > > have
> > > > responded to long ago:
> > > >
> > > > On Wed, Aug 31, 2016 at 02:23:48AM +0530, Bhaktipriya Shridhar
> > > > wrote:
> > > > >
> > > > >
> > > > > The workqueue "callback_wq" queues a single work item &cb-
> > > > > >cb_work per
> > > > > nfsd4_callback instance and thus, it doesn't require
> > > > > execution ordering.
> > > >
> > > > What's "execution ordering"?
> > > >
>
> AIUI, it means that jobs are always run in the order queued and are
> serialized.
>
> >
> > >
> > > >
> > > > We definitely do depend on the fact that at most one of these
> > > > is running
> > > > at a time.
> > >
>
> We do?
>
> >
> > >
> > > If there can be multiple cb's and thus cb->cb_work's per
> > > callback_wq,
> > > it'd need explicit ordering. Is that the case?
> >
>
> These are basically client RPC tasks, and the cb_work just handles
> the
> submission into the client RPC state machine. Just because we're
> running
> several callbacks at the same time doesn't mean that they need to be
> strictly ordered. The client state machine can certainly handle
> running
> these in parallel.
>
> >
> > Yes, there can be multiple cb_work's.
> >
>
> Yes, but each is effectively a separate work unit. I see no reason
> why
> we'd need to order them at all.
>
There needs to be serialisation at the session level (i.e. the
callbacks have to respect the slot limits set by the client) however
there shouldn’t be a need for serialisation at the RPC level.
Cheers
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