linux-kernel - Re: [PATCH 07/10] decnet: Use rcu

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Message-Id: <1245843884.6695.54.camel@localhost.localdomain>
Date:	Wed, 24 Jun 2009 13:44:44 +0200
From:	Jesper Dangaard Brouer <hawk@...x.dk>
To:	Chrissie Caulfield <christine.caulfield@...glemail.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	dougthompson@...ssion.com, bluesmoke-devel@...ts.sourceforge.net,
	axboe@...nel.dk, Patrick McHardy <kaber@...sh.net>,
	Trond.Myklebust@...app.com, linux-wireless@...r.kernel.org,
	johannes@...solutions.net, yoshfuji@...ux-ipv6.org,
	shemminger@...ux-foundation.org, linux-nfs@...r.kernel.org,
	bfields@...ldses.org, neilb@...e.de, linux-ext4@...r.kernel.org,
	tytso@....edu, adilger@....com, netfilter-devel@...r.kernel.org
Subject: Re: [PATCH 07/10] decnet: Use rcu_barrier() on module unload.

On Wed, 2009-06-24 at 07:23 +0100, Chrissie Caulfield wrote:
> The issues with DECnet module unloading are a little more than just an
> RCU leak I think!
> 
> Though that area does need reviewing ... when I get some time.

Fine.  Now you have read my comment in the code, then there is a updated
patch below.  Will you ack-that?

-- 
Med venlig hilsen / Best regards
  Jesper Brouer
  ComX Networks A/S
  Linux Network developer
  Cand. Scient Datalog / MSc.
  Author of http://adsl-optimizer.dk
  LinkedIn: http://www.linkedin.com/in/brouer


[PATCH 07/10] decnet: Use rcu_barrier() on module unload.

From: Jesper Dangaard Brouer <hawk@...x.dk>

The decnet module unloading as been disabled with a '#if 0' statement,
because it have had issues.

We add a rcu_barrier() anyhow for correctness.

The maintainer (Chrissie Caulfield) will look into the unload issue
when time permits.

Signed-off-by: Jesper Dangaard Brouer <hawk@...x.dk>
---

 net/decnet/af_decnet.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)


diff --git a/net/decnet/af_decnet.c b/net/decnet/af_decnet.c
index d351b8d..bff12da 100644
--- a/net/decnet/af_decnet.c
+++ b/net/decnet/af_decnet.c
@@ -2393,6 +2393,10 @@ module_init(decnet_init);
  * Prevent DECnet module unloading until its fixed properly.
  * Requires an audit of the code to check for memory leaks and
  * initialisation problems etc.
+ *
+ * hawk@...x.dk 2009-06-19:
+ *  I have added a rcu_barrier() which should plug some of your
+ *  module unload issues.  Maintainers please try it out...
  */
 #if 0
 static void __exit decnet_exit(void)
@@ -2413,6 +2417,8 @@ static void __exit decnet_exit(void)
 	proc_net_remove(&init_net, "decnet");
 
 	proto_unregister(&dn_proto);
+
+	rcu_barrier_bh(); /* Wait for completion of call_rcu_bh()'s */
 }
 module_exit(decnet_exit);
 #endif


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