netdev - Re: [PATCH net] ipv4: Silence suspicious RCU usage warning

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Message-Id: <20200729.121332.1722544892017052313.davem@davemloft.net>
Date:   Wed, 29 Jul 2020 12:13:32 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     idosch@...sch.org
Cc:     netdev@...r.kernel.org, kuba@...nel.org,
        alexander.h.duyck@...el.com, jiri@...lanox.com, mlxsw@...lanox.com,
        idosch@...lanox.com
Subject: Re: [PATCH net] ipv4: Silence suspicious RCU usage warning

From: Ido Schimmel <idosch@...sch.org>
Date: Wed, 29 Jul 2020 11:37:13 +0300

> From: Ido Schimmel <idosch@...lanox.com>
> 
> fib_trie_unmerge() is called with RTNL held, but not from an RCU
> read-side critical section. This leads to the following warning [1] when
> the FIB alias list in a leaf is traversed with
> hlist_for_each_entry_rcu().
> 
> Since the function is always called with RTNL held and since
> modification of the list is protected by RTNL, simply use
> hlist_for_each_entry() and silence the warning.
> 
> [1]
> WARNING: suspicious RCU usage
> 5.8.0-rc4-custom-01520-gc1f937f3f83b #30 Not tainted
> -----------------------------
> net/ipv4/fib_trie.c:1867 RCU-list traversed in non-reader section!!
 ...
> Fixes: 0ddcf43d5d4a ("ipv4: FIB Local/MAIN table collapse")
> Signed-off-by: Ido Schimmel <idosch@...lanox.com>
> Reviewed-by: Jiri Pirko <jiri@...lanox.com>

Also applied, thanks.