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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:

Looking through the net/ directory for call_rcu() users and unloadable
modules I found 5 modules that didn't behave correctly:






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

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