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

[Hangbin Liu <liuhangbin@gmail.com>]

On Mon, Dec 22, 2025 at 10:15:07PM +0800, Tonghao Zhang wrote:
> 
> 
> > On Dec 1, 2025, at 15:35, Hangbin Liu <liuhangbin@gmail.com> wrote:
> > 
> > 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.
> Yes, but Paolo suggested that put it in a separate patch file, because this code is unrelated from patch02. It's all good to me.
> “”"
> 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, then let's follow Paolo's suggestion.

Hangbin