On 05/20/2015 07:38 PM, Cong Wang wrote:
...
Why synchronize_rcu() even matters here? It waits for
readers, not for RCU callbacks.
Hm, I am mentioning it here as it was related to 78fd1d0ab072
as explained in the commit message.
Since we came here via unregister_tcf_proto_ops(), there
are no users of a given classifier anymore. Further nested
call_rcu()s pointing into the module space are not being
done anywhere.
This doesn't look like the best way to fix it, since calling
call_rcu() is tc filter specific, so why not just move the
rcu_barrier() to each of the ->destroy() implementation?
Let each filter handle its own implementation bug.
Effectively, every in-tree classifier (rsvp is the only exception)
is making use of call_rcu(). Moreover, moving this into every
->destroy() handler would also be unnecessary overhead, imho, as
this is only relevant when we actually _unload_ a module.
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