On Wed, 2015-09-02 at 13:58 -0700, Martin KaFai Lau wrote: > On Tue, Sep 01, 2015 at 01:14:20PM -0700, Eric Dumazet wrote: > > > 2. Use a spinlock to protect the dst_cache operations > > > > Well, a seqlock would be better : No need for an atomic operation in > > fast path. > > > seqlock can ensure consistency between idst->dst and idst->cookie. > However, IPv6 dst destruction is not protected by rcu. dst_free() is > directly called, like in ip6_fib.c and a few other places. > Hence, atomic_inc_not_zero() cannot be used here because the dst may > have already been kmem_cache_free() when refcnt is 0.
Really ? What about basic rcu rules ? Object cannot be freed until all cpus have exited their RCU sections. > A spinlock is > needed to stop the ip6_tnl_dst_set() side from removing the refcnt. Are you telling me RCU should be banished from the kernel ? ;) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
