netdev - About ip6_dst

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Date:   Sat, 27 Apr 2019 16:56:20 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     David Ahern <dsahern@...il.com>,
        Networking <netdev@...r.kernel.org>
Subject: About ip6_dst_destroy()

David

I am staring at ip6_dst_destroy() and the last part makes really no sense to me.

How rcu_read_lock()/rcu_read_unnlock() can help in a writer side ???

Changlog of a68886a691804d3f6d479ebf6825480fbafb6a00 ("net/ipv6: Make from in rt6_info rcu protected")
does not make sense either.

<quote>
    There is a race window when a FIB entry is deleted and the 'from' on the
    pcpu route is dropped and the pcpu route hits a cookie check. Handle
    this race using rcu on from.
</quote>