netdev - Re: [PATCH 4/5] sctp: protocol.c call rcu

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Message-ID: <20090608162227.GE6961@linux.vnet.ibm.com>
Date:	Mon, 8 Jun 2009 09:22:27 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Jesper Dangaard Brouer <hawk@...x.dk>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, urs.thuermann@...kswagen.de,
	oliver.hartkopp@...kswagen.de, wg@...ndegger.com,
	vladislav.yasevich@...com, sri@...ibm.com,
	linux-sctp@...r.kernel.org, Trond.Myklebust@...app.com,
	linux-nfs@...r.kernel.org, netfilter-devel@...r.kernel.org
Subject: Re: [PATCH 4/5] sctp: protocol.c call rcu_barrier() on unload.

On Mon, Jun 08, 2009 at 03:11:43PM +0200, Jesper Dangaard Brouer wrote:
> On module unload call rcu_barrier(), this is needed as synchronize_rcu()
> is not strong enough.  The kmem_cache_destroy() does invoke
> synchronize_rcu() but it does not provide same protection.

Good, looks like sctp_v4_del_protocol() invokes call_rcu(), which the
rcu_barrier() would then wait for.  And it looks like sctp_v6_del_protocol()
does the same for IPv6.

Reviewed_by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

> Signed-off-by: Jesper Dangaard Brouer <hawk@...x.dk>
> ---
> 
>  net/sctp/protocol.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
> index cb2c50d..79cbd47 100644
> --- a/net/sctp/protocol.c
> +++ b/net/sctp/protocol.c
> @@ -1370,6 +1370,8 @@ SCTP_STATIC __exit void sctp_exit(void)
>  	sctp_proc_exit();
>  	cleanup_sctp_mibs();
> 
> +	rcu_barrier(); /* Wait for completion of call_rcu()'s */
> +
>  	kmem_cache_destroy(sctp_chunk_cachep);
>  	kmem_cache_destroy(sctp_bucket_cachep);
>  }
> 
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