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

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Date: Thu, 20 Jun 2024 17:08:48 +0800
From: Hangbin Liu <liuhangbin@...il.com>
To: Nikolay Aleksandrov <razor@...ckwall.org>
Cc: netdev@...r.kernel.org, Jay Vosburgh <j.vosburgh@...il.com>,
	Andy Gospodarek <andy@...yhouse.net>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Jiri Pirko <jiri@...nulli.us>,
	Daniel Borkmann <daniel@...earbox.net>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Lorenzo Bianconi <lorenzo@...nel.org>,
	Ido Schimmel <idosch@...dia.com>, Amit Cohen <amcohen@...dia.com>
Subject: Re: [PATCH net-next] bonding: 3ad: send rtnl ifinfo notify when mux
 state changed

Hi Nikolay,
On Thu, Jun 20, 2024 at 11:47:46AM +0300, Nikolay Aleksandrov wrote:
> On 6/20/24 09:10, Hangbin Liu wrote:
> > Currently, administrators need to retrieve LACP mux state changes from
> > the kernel DEBUG log using netdev_dbg and slave_dbg macros. To simplify
> > this process, let's send the ifinfo notification whenever the mux state
> > changes. This will enable users to directly access and monitor this
> > information using the ip monitor command.
> > 
> > To achieve this, add a new enum NETDEV_LACP_STATE_CHANGE in netdev_cmd.
> > 
> > Signed-off-by: Hangbin Liu <liuhangbin@...il.com>
> > ---
> >  drivers/net/bonding/bond_3ad.c | 2 ++
> >  include/linux/netdevice.h      | 1 +
> >  net/core/dev.c                 | 2 +-
> >  net/core/rtnetlink.c           | 1 +
> >  4 files changed, 5 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c
> > index c6807e473ab7..bcd8b16173f2 100644
> > --- a/drivers/net/bonding/bond_3ad.c
> > +++ b/drivers/net/bonding/bond_3ad.c
> > @@ -1185,6 +1185,8 @@ static void ad_mux_machine(struct port *port, bool *update_slave_arr)
> >  		default:
> >  			break;
> >  		}
> > +
> > +		call_netdevice_notifiers(NETDEV_LACP_STATE_CHANGE, port->slave->dev);
> >  	}
> 
> This will cause sleeping while atomic because
> ad_mux_machine() is called in atomic context (both rcu and bond mode
> spinlock held with bh disabled) in bond_3ad_state_machine_handler().

Ah, that's why we call the bond_slave_state_notify() after spin_unlock_bh()?
Where can I check if call_netdevice_notifiers() would sleep? So I can avoid
this error next time.

> Minor (and rather more personal pref) I'd split the addition of the new
> event and adding its first user (bond) for separate review.

Hmm, with out using call_netdevice_notifiers(). How about just call
rtmsg_ifinfo() or rtmsg_ifinfo_event() directly?

Thanks
Hangbin