Re: [PATCH 5/5] sunrpc/auth_gss: Call rcu_barrier() on module unload.

[Trond Myklebust <Trond.Myklebust@netapp.com>]

On Mon, 2009-06-08 at 09:26 -0700, Paul E. McKenney wrote:
> On Mon, Jun 08, 2009 at 03:11:48PM +0200, Jesper Dangaard Brouer wrote:
> > As the module uses rcu_call() we should make sure that all
> > rcu callback has been completed before removing the code.
> 
> Good improvement!!!  Assuming that gss_svc_shutdown() and
> rpcauth_unregister() prevent any future RCU callbacks to be registered,
> this patch will fix things up.
> 
> Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> 
> > Signed-off-by: Jesper Dangaard Brouer <hawk-4UpuNZONu4c@public.gmane.org>
> > ---
> > 
> >  net/sunrpc/auth_gss/auth_gss.c |    1 +
> >  1 files changed, 1 insertions(+), 0 deletions(-)
> > 
> > diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c
> > index e630b38..66d458f 100644
> > --- a/net/sunrpc/auth_gss/auth_gss.c
> > +++ b/net/sunrpc/auth_gss/auth_gss.c
> > @@ -1548,6 +1548,7 @@ static void __exit exit_rpcsec_gss(void)
> >  {
> >  	gss_svc_shutdown();
> >  	rpcauth_unregister(&authgss_ops);
> > +	rcu_barrier(); /* Wait for completion of call_rcu()'s */
> >  }
> > 
> >  MODULE_LICENSE("GPL");
> > 

Hmm... If this is about ensuring that all the call_rcu() callbacks
complete before we remove the module, then don't we also need similar
barriers in net/sunrpc/sunrpc_syms.c:cleanup_sunrpc() and in
fs/nfs/inode.c:exit_nfs_fs()?

Cheers
  Trond
-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com
www.netapp.com