bonding: Convert balance-rr transmit to new locking

	Change locking in balance-rr transmit processing to use a free
running counter to determine which slave to transmit on.  Instead, a
free-running counter is maintained, and modulo arithmetic used to select
a slave for transmit.

	This removes lock operations from the TX path, and eliminates
a deadlock introduced by the conversion to work queues.

Signed-off-by: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

1 files changed, 12 insertions, 13 deletions

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index ed361d62d702..862ed8ece14e 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -4057,8 +4057,7 @@ static int bond_xmit_roundrobin(struct sk_buff *skb, struct net_device *bond_dev
 {
         struct bonding *bond = bond_dev->priv;
         struct slave *slave, *start_at;
-        int i;
-        int res = 1;
+        int i, slave_no, res = 1;
 
         read_lock(&bond->lock);
 
@@ -4066,29 +4065,29 @@ static int bond_xmit_roundrobin(struct sk_buff *skb, struct net_device *bond_dev
                 goto out;
         }
 
-        read_lock(&bond->curr_slave_lock);
-        slave = start_at = bond->curr_active_slave;
-        read_unlock(&bond->curr_slave_lock);
+        /*
+         * Concurrent TX may collide on rr_tx_counter; we accept that
+         * as being rare enough not to justify using an atomic op here
+         */
+        slave_no = bond->rr_tx_counter++ % bond->slave_cnt;
 
-        if (!slave) {
-                goto out;
+        bond_for_each_slave(bond, slave, i) {
+                slave_no--;
+                if (slave_no < 0) {
+                        break;
+                }
         }
 
+        start_at = slave;
         bond_for_each_slave_from(bond, slave, i, start_at) {
                 if (IS_UP(slave->dev) &&
                     (slave->link == BOND_LINK_UP) &&
                     (slave->state == BOND_STATE_ACTIVE)) {
                         res = bond_dev_queue_xmit(bond, skb, slave->dev);
-
-                        write_lock(&bond->curr_slave_lock);
-                        bond->curr_active_slave = slave->next;
-                        write_unlock(&bond->curr_slave_lock);
-
                         break;
                 }
         }
 
-
 out:
         if (res) {
                 /* no suitable interface, frame not sent */