Re: [PATCH v4 net-next 01/12] bonding: remove bond->lock from bond_arp_rcv

On Tue, Feb 18, 2014 at 12:02:41PM +0800, Ding Tianhong wrote:

On 2014/2/17 22:41, Veaceslav Falico wrote:

quoted

We're always called with rcu_read_lock() held (bond_arp_rcv() is only
called from bond_handle_frame(), which is rx_handler and always called
under rcu from __netif_receive_skb_core() ).

The slave active/passive and/or bonding params can change in-flight, however
we don't really care about that - we only modify the last time packet was
received, which is harmless.

CC: Jay Vosburgh <redacted>
CC: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: Veaceslav Falico <redacted>
---
 drivers/net/bonding/bond_main.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 3bce855..3c50bec 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c

@@ -2260,8 +2260,6 @@ int bond_arp_rcv(const struct sk_buff *skb, struct bonding *bond,
 	if (skb->protocol != __cpu_to_be16(ETH_P_ARP))
 		return RX_HANDLER_ANOTHER;

-	read_lock(&bond->lock);
-
 	if (!slave_do_arp_validate(bond, slave))
 		goto out_unlock;

@@ -2318,7 +2316,6 @@ int bond_arp_rcv(const struct sk_buff *skb, struct bonding *bond,
 		bond_validate_arp(bond, slave, tip, sip);

 out_unlock:
-	read_unlock(&bond->lock);
 	if (arp != (struct arphdr *)skb->data)
 		kfree(arp);
 	return RX_HANDLER_ANOTHER;

I think it is not enough, you should add rcu_dereference for bond->curr_active_slave, it may be changed during
the recv processing.

bond->lock has absolutely nothing to du with bond->curr_active_slave .

Regards
Ding