From: Roopa Prabhu <ro...@cumulusnetworks.com> Date: Wed, 16 May 2018 13:30:28 -0700
> yes, but we hold rcu read lock before calling the reply function for > fib result. I did consider allocating the skb before the read > lock..but then the refactoring (into a separate netlink reply func) > would seem unnecessary. > > I am fine with pre-allocating and undoing the refactoring if that works > better. Hmmm... I also notice that with this change we end up doing the rtnl_unicast() under the RCU lock which is unnecessary too. So yes, please pull the "out_skb" allocation before the rcu_read_lock(), and push the rtnl_unicast() after the rcu_read_unlock(). It really is a shame that sharing the ETH_P_IP skb between the route route lookup and the netlink response doesn't work properly. I was using RTM_GETROUTE at one point for route/fib lookup performance measurements. It never was great at that, but now that there is going to be two SKB allocations instead of one it is going to be even less useful for that kind of usage.
