netdev - Re: [PATCH net-next v1] net: bonding: move bond_should_notify

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Message-Id: <66B650E7-EBE7-48F4-8B05-F294C2F4964C@bamaicloud.com>
Date: Sun, 23 Nov 2025 21:30:58 +0800
From: Tonghao Zhang <tonghao@...aicloud.com>
To: Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org,
 Jay Vosburgh <jv@...sburgh.net>,
 "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>,
 Simon Horman <horms@...nel.org>,
 Jonathan Corbet <corbet@....net>,
 Andrew Lunn <andrew+netdev@...n.ch>,
 Nikolay Aleksandrov <razor@...ckwall.org>,
 Hangbin Liu <liuhangbin@...il.com>
Subject: Re: [PATCH net-next v1] net: bonding: move bond_should_notify_peers,
 e.g. into rtnl lock block



> On Nov 20, 2025, at 20:53, Paolo Abeni <pabeni@...hat.com> wrote:
> 
> On 11/18/25 10:04 AM, Tonghao Zhang wrote:
>> In bond_mii_monitor()/bond_activebackup_arp_mon(), when we hold the rtnl lock:
>> 
>> - check send_peer_notif again to avoid unconditionally reducing this value.
>> - send_peer_notif may have been reset. Therefore, it is necessary to check
>>  whether to send peer notify via bond_should_notify_peers() to avoid the
>>  loss of notification events.
> 
> This looks strictly related to:
> 
> https://patchwork.kernel.org/project/netdevbpf/patch/20251118090305.35558-1-tonghao@bamaicloud.com/
> 
> you probably should bundle both in a series.
Ok
> 
>> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>> index b7370c918978..6f0fa78fa3f3 100644
>> --- a/drivers/net/bonding/bond_main.c
>> +++ b/drivers/net/bonding/bond_main.c
>> @@ -2810,11 +2810,10 @@ static void bond_mii_monitor(struct work_struct *work)
>> {
>> struct bonding *bond = container_of(work, struct bonding,
>>    mii_work.work);
>> - bool should_notify_peers;
>> - bool commit;
>> - unsigned long delay;
>> - struct slave *slave;
>> struct list_head *iter;
>> + struct slave *slave;
>> + unsigned long delay;
>> + bool commit;
>> 
>> delay = msecs_to_jiffies(bond->params.miimon);
>> 
>> @@ -2823,7 +2822,6 @@ static void bond_mii_monitor(struct work_struct *work)
>> 
>> rcu_read_lock();
>> 
>> - should_notify_peers = bond_should_notify_peers(bond);
>> commit = !!bond_miimon_inspect(bond);
>> 
>> rcu_read_unlock();
>> @@ -2844,10 +2842,10 @@ static void bond_mii_monitor(struct work_struct *work)
>> }
>> 
>> if (bond->send_peer_notif) {
> 
> The first `bond->send_peer_notif` access is outside the lock. I think
> the compiler could do funny things and read the field only outside the
> lock: I guess you need additional ONCE annotation, and that could be a
> separate patch.
Ok
> 
>> - bond->send_peer_notif--;
>> - if (should_notify_peers)
>> + if (bond_should_notify_peers(bond))
>> call_netdevice_notifiers(NETDEV_NOTIFY_PEERS,
>> bond->dev);
>> + bond->send_peer_notif--;
>> }
>> 
>> rtnl_unlock(); /* might sleep, hold no other locks */
>> @@ -3759,8 +3757,7 @@ static bool bond_ab_arp_probe(struct bonding *bond)
>> 
>> static void bond_activebackup_arp_mon(struct bonding *bond)
>> {
>> - bool should_notify_peers = false;
>> - bool should_notify_rtnl = false;
>> + bool should_notify_rtnl;
>> int delta_in_ticks;
>> 
>> delta_in_ticks = msecs_to_jiffies(bond->params.arp_interval);
>> @@ -3770,15 +3767,12 @@ static void bond_activebackup_arp_mon(struct bonding *bond)
>> 
>> rcu_read_lock();
>> 
>> - should_notify_peers = bond_should_notify_peers(bond);
>> -
>> if (bond_ab_arp_inspect(bond)) {
>> rcu_read_unlock();
>> 
>> /* Race avoidance with bond_close flush of workqueue */
>> if (!rtnl_trylock()) {
>> delta_in_ticks = 1;
>> - should_notify_peers = false;
>> goto re_arm;
>> }
>> 
>> @@ -3791,18 +3785,15 @@ static void bond_activebackup_arp_mon(struct bonding *bond)
>> should_notify_rtnl = bond_ab_arp_probe(bond);
>> rcu_read_unlock();
>> 
>> -re_arm:
>> - if (bond->params.arp_interval)
>> - queue_delayed_work(bond->wq, &bond->arp_work, delta_in_ticks);
>> -
>> - if (should_notify_peers || should_notify_rtnl) {
>> + if (bond->send_peer_notif || should_notify_rtnl) {
>> if (!rtnl_trylock())
>> return;
> 
> The above skips the 2nd trylock attempt when the first one fail, which
> IMHO makes sense, but its unrelated from the rest of the change here. I
> think this specific bits should go in a separate patch.
Ok, thanks.
> 
> /P
> 
> 
>