netdev - Re: [PATCH net] route: add rcu_read_lock when lookup route and update fnhe in __ip_do

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Date:	Tue, 2 Feb 2016 01:16:03 +0800
From:	Xin Long <lucien.xin@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	network dev <netdev@...r.kernel.org>, davem <davem@...emloft.net>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>
Subject: Re: [PATCH net] route: add rcu_read_lock when lookup route and update
 fnhe in __ip_do_redirect

>
> But the whole __ip_do_redirect() needs to be called from rcu_read_lock()
> already.
>
> No need to add another rcu_read_lock() around fib_lookup()
>
> How did you come doing this patch ? Any particular stack dump or
> something ?
>
no, no stack dump was found.
by reviewing code, I found it when I cooked another patch.

and the path that __ip_do_redirect() is called should be:

icmp_rcv |-> icmp_unreach  -\
              |-> icmp_redirect -> icmp_socket_deliver -> ipprot->err_handler()
[tcp_v4/6_err, sctp_v4/6_err, dccp_v4/6_err, udpv4/6_err ...]

-> ... -> __ip_do_redirect()

I checked the codes for many times, didn't find any rcu_lock on this path,
unless we treat BH as rcu_lock.

did I miss something ?

Thanks.

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