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Message-ID: <20090608130959.10052.54590.stgit@localhost>
Date: Mon, 08 Jun 2009 15:11:23 +0200
From: Jesper Dangaard Brouer <hawk@...x.dk>
To: "David S. Miller" <davem@...emloft.net>
Cc: Jesper Dangaard Brouer <hawk@...x.dk>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
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: [PATCH 0/5] We must use rcu_barrier() on module unload
If an unloadable module uses RCU callbacks, it need to use
rcu_barrier() so that the module may be safely unloaded.
While hacking on a netfilter module of my own, I learned the
importance of calling rcu_barrier() instead of only a
synchronize_rcu() on module unload (iif using any call_rcu()
callbacks). synchronize_rcu() does wait for a grace period to
elapse, but it does not wait for the callbacks to complete.
For documentation see:
http://lwn.net/Articles/217484/
Documentation/RCU/rcubarrier.txt
Looking through the net/ directory for call_rcu() users and unloadable
modules I found 5 modules that didn't behave correctly:
net/8021q/vlan.c
net/can/af_can.c
net/netfilter/nfnetlink_queue.c
net/sctp/protocol.c
net/sunrpc/auth_gss/auth_gss.c
I have made a patch for each individual module, so objections can be
made on a per module basis. I have Cc'ed all of the patches to the
maintainers of each module (according to the MAINTAINERS file).
The patchset is made on top of DaveM's net-next-2.6 tree (starting on
top of commit a1c1db392090). As this is my usual development tree,
even though this patchset is bugfixes. (Just tested it applied cleanly
on Linus'es tree ...)
---
Jesper Dangaard Brouer (5):
sunrpc/auth_gss: Call rcu_barrier() on module unload.
sctp: protocol.c call rcu_barrier() on unload.
can: af_can.c use rcu_barrier() on module unload.
nfnetlink_queue: Use rcu_barrier() on module unload.
8021q: Vlan driver should use rcu_barrier() on unload instead of syncronize_net()
net/8021q/vlan.c | 2 +-
net/can/af_can.c | 2 ++
net/netfilter/nfnetlink_queue.c | 4 +++-
net/sctp/protocol.c | 2 ++
net/sunrpc/auth_gss/auth_gss.c | 1 +
5 files changed, 9 insertions(+), 2 deletions(-)
--
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
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