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 -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
