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    Subject[PATCH 0/5] We must use rcu_barrier() on module unload
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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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