netdev - Re: [RFC PATCH 2/2] net: bonding: don't call ethtool methods under RCU

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Message-ID: <Zpo27pq6lWYyVv_y@nanopsycho.orion>
Date: Fri, 19 Jul 2024 11:50:38 +0200
From: Jiri Pirko <jiri@...nulli.us>
To: Johannes Berg <johannes@...solutions.net>
Cc: netdev@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
	Johannes Berg <johannes.berg@...el.com>,
	syzbot+2120b9a8f96b3fa90bad@...kaller.appspotmail.com
Subject: Re: [RFC PATCH 2/2] net: bonding: don't call ethtool methods under
 RCU

Thu, Jul 18, 2024 at 09:20:17PM CEST, johannes@...solutions.net wrote:
>From: Johannes Berg <johannes.berg@...el.com>
>
>Currently, bond_miimon_inspect() is called under RCU, but it
>calls ethtool ops. Since my earlier commit facd15dfd691
>("net: core: synchronize link-watch when carrier is queried")
>this is no longer permitted in the general ethtool case, but
>it was already not permitted for many drivers such as USB in
>which it can sleep to do MDIO register accesses etc.
>
>Therefore, it's better to simply not do this. Change bonding
>to acquire the RTNL for the MII monitor work directly to call
>the bond_miimon_inspect() function and thus ethtool ops.

Is there a good reason why to directly query device here using whatever?
I mean, why netif_oper_up() would not return the correct bool here?
Introduction of periodic rtnl locking for no good reason is not probably
something we should do :/