From: Ido Schimmel <idosch@idosch.org>
To: Florian Westphal <fw@strlen.de>
Cc: netdev@vger.kernel.org
Subject: Re: [PATCH net-next 1/6] rtnetlink: use rcu_dereference_raw to silence rcu splat
Date: Thu, 10 Aug 2017 18:38:15 +0300 [thread overview]
Message-ID: <20170810153815.GA22889@splinter> (raw)
In-Reply-To: <20170810145302.30391-2-fw@strlen.de>
On Thu, Aug 10, 2017 at 04:52:57PM +0200, Florian Westphal wrote:
> Ido reports a rcu splat in __rtnl_register.
> The splat is correct; as rtnl_register doesn't grab any logs
> and doesn't use rcu locks either. It has always been like this.
> handler families are not registered in parallel so there are no
> races wrt. the kmalloc ordering.
>
> The only reason to use rcu_dereference in the first place was to
> avoid sparse from complaining about this.
>
> Thus this switches to _raw() to not have rcu checks here.
>
> The alternative is to add rtnl locking to register/unregister,
> however, I don't see a compelling reason to do so as this has been
> lockless for the past twenty years or so.
>
> Fixes: 6853dd4881 ("rtnetlink: protect handler table with rcu")
> Reported-by: Ido Schimmel <idosch@idosch.org>
> Signed-off-by: Florian Westphal <fw@strlen.de>
Tested-by: Ido Schimmel <idosch@mellanox.com>
Thanks!
next prev parent reply other threads:[~2017-08-10 15:51 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-10 14:52 [PATCH net-next 0/6] rtnetlink: fix initial rtnl pushdown fallout Florian Westphal
2017-08-10 14:52 ` [PATCH net-next 1/6] rtnetlink: use rcu_dereference_raw to silence rcu splat Florian Westphal
2017-08-10 15:38 ` Ido Schimmel [this message]
2017-08-10 14:52 ` [PATCH net-next 2/6] rtnetlink: do not use RTM_GETLINK directly Florian Westphal
2017-08-10 14:52 ` [PATCH net-next 3/6] rtnetlink: switch rtnl_link_get_slave_info_data_size to rcu Florian Westphal
2017-08-10 16:17 ` David Ahern
2017-08-10 14:53 ` [PATCH net-next 4/6] rtnetlink: init handler refcounts to 1 Florian Westphal
2017-08-10 14:53 ` [PATCH net-next 5/6] rtnetlink: fallback to UNSPEC if current family has no doit callback Florian Westphal
2017-08-10 14:53 ` [PATCH net-next 6/6] selftests: add rtnetlink test script Florian Westphal
2017-08-10 16:50 ` [PATCH net-next 0/6] rtnetlink: fix initial rtnl pushdown fallout David Miller
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