linux-kernel - Re: [PATCH 5/5] sunrpc/auth_gss: Call rcu

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Message-ID: <Pine.LNX.4.64.0906082128240.1180@ask.diku.dk>
Date:	Mon, 8 Jun 2009 21:48:54 +0200 (CEST)
From:	Jesper Dangaard Brouer <hawk@...u.dk>
To:	Trond Myklebust <Trond.Myklebust@...app.com>
Cc:	paulmck@...ux.vnet.ibm.com, Jesper Dangaard Brouer <hawk@...x.dk>,
	netdev <netdev@...r.kernel.org>, linux-kernel@...r.kernel.org,
	linux-nfs@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH 5/5] sunrpc/auth_gss: Call rcu_barrier() on module unload.

(trimmed Cc)

On Mon, 8 Jun 2009, Trond Myklebust wrote:

> 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

Well, Trond that was a hard question, as I don't know this code... but if 
it uses call_rcu() callbacks its most likely.

I have not done a complete sweep of the tree, I have only looked at the 
netdev parts, as this is where I usually snoop around.  So there is 
probably plenty of work for some kernel-janitors (Cc'ing the list ;-))

> net/sunrpc/sunrpc_syms.c:cleanup_sunrpc()

Looking at the code that end up in sunrpc.ko, I see that both 
net/sunrpc/auth_unix.c and net/sunrpc/auth_generic.c uses call_rcu() 
callbacks.

> and in fs/nfs/inode.c:exit_nfs_fs()?

Looking at the code which end up into nfs.ko (which includes 
fs/nfs/inode.c) I see that the fs/nfs/delegation.c uses call_rcu() 
callbacks.

But its hard for me to figure out how this code interacts.  Don't know if 
we need to document a code path that can occur fast enough, before we add 
this safe guard?  It should be Paul's saying...

Cheers,
   Jesper Brouer

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