Re: [PATCH net-next v3 3/4] net: bonding: skip the 2nd trylock when first one fail

[Hangbin Liu <liuhangbin@gmail.com>]

On Sun, Nov 30, 2025 at 03:48:45PM +0800, Tonghao Zhang wrote:
> After the first trylock fail, retrying immediately is
> not advised as there is a high probability of failing
> to acquire the lock again. This optimization makes sense.
> 
> Cc: Jay Vosburgh <jv@jvosburgh.net>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Jakub Kicinski <kuba@kernel.org>
> Cc: Paolo Abeni <pabeni@redhat.com>
> Cc: Simon Horman <horms@kernel.org>
> Cc: Jonathan Corbet <corbet@lwn.net>
> Cc: Andrew Lunn <andrew+netdev@lunn.ch>
> Cc: Nikolay Aleksandrov <razor@blackwall.org>
> Cc: Hangbin Liu <liuhangbin@gmail.com>
> Cc: Jason Xing <kerneljasonxing@gmail.com>
> Signed-off-by: Tonghao Zhang <tonghao@bamaicloud.com>
> ---
> v1:
> - splitted from: https://patchwork.kernel.org/project/netdevbpf/patch/20251118090431.35654-1-tonghao@bamaicloud.com/
> - this patch only skip the 2nd rtnl lock.
> - add this patch to series
> ---
>  drivers/net/bonding/bond_main.c | 16 +++++++++-------
>  1 file changed, 9 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index 1b16c4cd90e0..025ca0a45615 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -3756,7 +3756,7 @@ static bool bond_ab_arp_probe(struct bonding *bond)
>  
>  static void bond_activebackup_arp_mon(struct bonding *bond)
>  {
> -	bool should_notify_rtnl = false;
> +	bool should_notify_rtnl;
>  	int delta_in_ticks;
>  
>  	delta_in_ticks = msecs_to_jiffies(bond->params.arp_interval);
> @@ -3784,13 +3784,11 @@ 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 (bond->send_peer_notif || should_notify_rtnl) {
> -		if (!rtnl_trylock())
> -			return;
> +		if (!rtnl_trylock()) {
> +			delta_in_ticks = 1;
> +			goto re_arm;
> +		}
>  
>  		if (bond->send_peer_notif) {
>  			if (bond_should_notify_peers(bond))
> @@ -3805,6 +3803,10 @@ static void bond_activebackup_arp_mon(struct bonding *bond)
>  
>  		rtnl_unlock();
>  	}
> +
> +re_arm:
> +	if (bond->params.arp_interval)
> +		queue_delayed_work(bond->wq, &bond->arp_work, delta_in_ticks);
>  }
>  
>  static void bond_arp_monitor(struct work_struct *work)
> -- 
> 2.34.1
> 

Maybe this patch should be merged together with patch 02, since the issue
was introduced there. Before patch 02, both should_notify_peers and
should_notify_rtnl would be false when the first rtnl_trylock() failed,
so the second trylock() would never be called.

Thanks
Hangbin