netdev - Re: [PATCHv3 net-next] bonding: 3ad: send ifinfo notify when mux state changed

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Date: Thu, 27 Jun 2024 21:17:17 +0800
From: Hangbin Liu <liuhangbin@...il.com>
To: Nikolay Aleksandrov <razor@...ckwall.org>,
	Jay Vosburgh <jay.vosburgh@...onical.com>
Cc: Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
	Andy Gospodarek <andy@...yhouse.net>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
	Ido Schimmel <idosch@...dia.com>, Jiri Pirko <jiri@...nulli.us>,
	Amit Cohen <amcohen@...dia.com>
Subject: Re: [PATCHv3 net-next] bonding: 3ad: send ifinfo notify when mux
 state changed

On Thu, Jun 27, 2024 at 01:33:10PM +0300, Nikolay Aleksandrov wrote:
> > Yes, but at least the admin could get the latest state. With the following
> > code the admin may not get the latest update if lock rtnl failed.
> > 
> >         if (should_notify_rtnl && rtnl_trylock()) {
> >                 bond_slave_lacp_notify(bond);
> >                 rtnl_unlock();
> > 	}
> > 
> Well, you mentioned administrators want to see the state changes, please
> better clarify the exact end goal. Note that technically may even not be
> the last state as the state change itself happens in parallel (different
> locks) and any update could be delayed depending on rtnl availability
> and workqueue re-scheduling. But sure, they will get some update at some point. :)

Ah.. Yes, that's a sad fact :(
> 
> It all depends on what are the requirements.
> 
> An uglier but lockless alternative would be to poll the slave's sysfs oper state,
> that doesn't require any locks and would be up-to-date.

Hmm, that's a workaround, but the admin need to poll the state frequently as
they don't know when the state will change.

Hi Jay, are you OK to add this sysfs in bonding?

Thanks
Hangbin