Messages in this thread | | | From | Jesper Dangaard Brouer <> | Subject | [PATCH 0/5] We must use rcu_barrier() on module unload | Date | Mon, 08 Jun 2009 15:11:23 +0200 |
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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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