From: Greg Banks <gnb@sgi.com>
Subject: Re: [RFC,PATCH 11/35] svc: Add xpo_accept transport function
Date: Thu, 4 Oct 2007 11:54:48 +1000
Message-ID: <20071004015448.GT21388@sgi.com>
References: <20071001191426.3250.15371.stgit@dell3.ogc.int>
	<20071001192753.3250.94322.stgit@dell3.ogc.int>
	<EECEF6FF-4C84-4764-BF0B-383AA870AFDD@oracle.com>
	<1191343305.1565.24.camel@trinity.ogc.int>
	<325D6316-382E-45F5-BBB8-4BE40A637C53@oracle.com>
	<1191349734.1565.52.camel@trinity.ogc.int>
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Cc: neilb@suse.de, bfields@fieldses.org, nfs@lists.sourceforge.net
To: Tom Tucker <tom@opengridcomputing.com>
In-Reply-To: <1191349734.1565.52.camel@trinity.ogc.int>
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Errors-To: nfs-bounces@lists.sourceforge.net

On Tue, Oct 02, 2007 at 01:28:54PM -0500, Tom Tucker wrote:
> On Tue, 2007-10-02 at 13:07 -0400, Chuck Lever wrote:
> > On Oct 2, 2007, at 12:41 PM, Tom Tucker wrote:
> > > On Tue, 2007-10-02 at 11:33 -0400, Chuck Lever wrote:
> > >> On Oct 1, 2007, at 3:27 PM, Tom Tucker wrote:
> > >
> > > [...snip...]
> > >
> > >>> +		if (newxpt)
> > >>> +			svc_check_conn_limits(svsk->sk_server);
> > >>> +		svc_sock_received(svsk);
> > >>>  	} else {
> > >>>  		dprintk("svc: server %p, pool %u, socket %p, inuse=%d\n",
> > >>>  			rqstp, pool->sp_id, svsk, atomic_read(&svsk->sk_inuse));
> > >>
> > >> Instead of adding a test_bit() and conditional branch here, why not
> > >> always call xpo_accept?  For UDP, the method simply returns.
> > >>
> > >
> > > That's what I thought at first too, but UDP needs to call receive  
> > > here.
> > > Doing nothing stalls the service and lockd never gets set up.
> > 
> > The purpose of a transport switch is to force all the transport  
> > specific processing down into the transport implementation so you  
> > don't need these SK_ switches to decide whether or not to call a  
> > function based on which transport is in use.
> 
> I don't think it's doing that. I think it's checking the "role" of the
> instance; passive vs. active endpoint. The role is transport independent
> and is checked in the generic svc_recv function.

Yes, this is generic functionality that any connection-oriented
transport needs.  Two of the three transports we have use xpo_accept.

Fundamentally, the transport-independent core needs to be aware of the
difference between connectionless and connection-oriented transports.
It needs to do several special things for the latter.  Examples
include enforcing a connection limit, and caching client-related data
on the connection.

Greg.
-- 
Greg Banks, R&D Software Engineer, SGI Australian Software Group.
Apparently, I'm Bedevere.  Which MPHG character are you?
I don't speak for SGI.

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