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Date: Fri, 31 Aug 2012 00:02:47 +0200
From: Jiri Bohac <jbohac@...e.cz>
To: Jay Vosburgh <fubar@...ibm.com>
Cc: Chris Friesen <chris.friesen@...band.com>,
Jiri Bohac <jbohac@...e.cz>,
Andy Gospodarek <andy@...yhouse.net>, netdev@...r.kernel.org,
Petr Tesarik <ptesarik@...e.cz>, davem@...emloft.net
Subject: [PATCH] bonding: add some slack to arp monitoring time limits
Currently, all the time limits in the bonding ARP monitor are in
multiples of arp_interval -- the time interval at which the ARP
monitor is periodically scheduled.
With a fast network round-trip and a little scheduling latency
of the ARP monitor work, a limit of n*delta_in_ticks may
effectively mean (n-1)*delta_in_ticks.
This is fatal in case of n==1 (the link will stay down
forever) and makes the behaviour non-deterministic in all the
other cases.
Add a delta_in_ticks/2 time slack to all the time limits.
Signed-off-by: Jiri Bohac <jbohac@...e.cz>
diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 6fae5f3..0f04115 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -2813,12 +2813,13 @@ void bond_loadbalance_arp_mon(struct work_struct *work)
arp_work.work);
struct slave *slave, *oldcurrent;
int do_failover = 0;
- int delta_in_ticks;
+ int delta_in_ticks, extra_ticks;
int i;
read_lock(&bond->lock);
delta_in_ticks = msecs_to_jiffies(bond->params.arp_interval);
+ extra_ticks = delta_in_ticks / 2;
if (bond->slave_cnt == 0)
goto re_arm;
@@ -2841,10 +2842,10 @@ void bond_loadbalance_arp_mon(struct work_struct *work)
if (slave->link != BOND_LINK_UP) {
if (time_in_range(jiffies,
trans_start - delta_in_ticks,
- trans_start + delta_in_ticks) &&
+ trans_start + delta_in_ticks + extra_ticks) &&
time_in_range(jiffies,
slave->dev->last_rx - delta_in_ticks,
- slave->dev->last_rx + delta_in_ticks)) {
+ slave->dev->last_rx + delta_in_ticks + extra_ticks)) {
slave->link = BOND_LINK_UP;
bond_set_active_slave(slave);
@@ -2874,10 +2875,10 @@ void bond_loadbalance_arp_mon(struct work_struct *work)
*/
if (!time_in_range(jiffies,
trans_start - delta_in_ticks,
- trans_start + 2 * delta_in_ticks) ||
+ trans_start + 2 * delta_in_ticks + extra_ticks) ||
!time_in_range(jiffies,
slave->dev->last_rx - delta_in_ticks,
- slave->dev->last_rx + 2 * delta_in_ticks)) {
+ slave->dev->last_rx + 2 * delta_in_ticks + extra_ticks)) {
slave->link = BOND_LINK_DOWN;
bond_set_backup_slave(slave);
@@ -2935,6 +2936,14 @@ static int bond_ab_arp_inspect(struct bonding *bond, int delta_in_ticks)
struct slave *slave;
int i, commit = 0;
unsigned long trans_start;
+ int extra_ticks;
+
+ /* All the time comparisons below need some extra time. Otherwise, on
+ * fast networks the ARP probe/reply may arrive within the same jiffy
+ * as it was sent. Then, the next time the ARP monitor is run, one
+ * arp_interval will already have passed in the comparisons.
+ */
+ extra_ticks = delta_in_ticks / 2;
bond_for_each_slave(bond, slave, i) {
slave->new_link = BOND_LINK_NOCHANGE;
@@ -2942,7 +2951,7 @@ static int bond_ab_arp_inspect(struct bonding *bond, int delta_in_ticks)
if (slave->link != BOND_LINK_UP) {
if (time_in_range(jiffies,
slave_last_rx(bond, slave) - delta_in_ticks,
- slave_last_rx(bond, slave) + delta_in_ticks)) {
+ slave_last_rx(bond, slave) + delta_in_ticks + extra_ticks)) {
slave->new_link = BOND_LINK_UP;
commit++;
@@ -2958,7 +2967,7 @@ static int bond_ab_arp_inspect(struct bonding *bond, int delta_in_ticks)
*/
if (time_in_range(jiffies,
slave->jiffies - delta_in_ticks,
- slave->jiffies + 2 * delta_in_ticks))
+ slave->jiffies + 2 * delta_in_ticks + extra_ticks))
continue;
/*
@@ -2978,7 +2987,7 @@ static int bond_ab_arp_inspect(struct bonding *bond, int delta_in_ticks)
!bond->current_arp_slave &&
!time_in_range(jiffies,
slave_last_rx(bond, slave) - delta_in_ticks,
- slave_last_rx(bond, slave) + 3 * delta_in_ticks)) {
+ slave_last_rx(bond, slave) + 3 * delta_in_ticks + extra_ticks)) {
slave->new_link = BOND_LINK_DOWN;
commit++;
@@ -2994,10 +3003,10 @@ static int bond_ab_arp_inspect(struct bonding *bond, int delta_in_ticks)
if (bond_is_active_slave(slave) &&
(!time_in_range(jiffies,
trans_start - delta_in_ticks,
- trans_start + 2 * delta_in_ticks) ||
+ trans_start + 2 * delta_in_ticks + extra_ticks) ||
!time_in_range(jiffies,
slave_last_rx(bond, slave) - delta_in_ticks,
- slave_last_rx(bond, slave) + 2 * delta_in_ticks))) {
+ slave_last_rx(bond, slave) + 2 * delta_in_ticks + extra_ticks))) {
slave->new_link = BOND_LINK_DOWN;
commit++;
@@ -3029,7 +3038,7 @@ static void bond_ab_arp_commit(struct bonding *bond, int delta_in_ticks)
if ((!bond->curr_active_slave &&
time_in_range(jiffies,
trans_start - delta_in_ticks,
- trans_start + delta_in_ticks)) ||
+ trans_start + delta_in_ticks + delta_in_ticks / 2)) ||
bond->curr_active_slave != slave) {
slave->link = BOND_LINK_UP;
if (bond->current_arp_slave) {
--
Jiri Bohac <jbohac@...e.cz>
SUSE Labs, SUSE CZ
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