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Date: Wed, 1 Sep 2010 15:16:26 +0200
From: Jiri Bohac <jbohac@...e.cz>
To: Jay Vosburgh <fubar@...ibm.com>
Cc: Jiri Bohac <jbohac@...e.cz>, bonding-devel@...ts.sourceforge.net,
markine@...gle.com, jarkao2@...il.com, chavey@...gle.com,
netdev@...r.kernel.org
Subject: Re: [RFC] bonding: fix workqueue re-arming races
On Tue, Aug 31, 2010 at 01:54:23PM -0700, Jay Vosburgh wrote:
> Jiri Bohac <jbohac@...e.cz> wrote:
> >[note, this does not deal with bond_loadbalance_arp_mon(), where
> >rtnl is now taken as well in net-next; I'll do this if you think
> >the idea is good ]
>
> I don't believe the loadbalance_arp_mon acquires RTNL in
> net-next. I recall discussing this with Andy not too long ago, but I
> didn't think that change went in, and I don't see it in the tree.
Of course, you are right, I misread the e-mail thread and did not look at
the code.
> >+void bond_alb_promisc_disable(struct work_struct *work)
> >+{
> >+ struct bonding *bond = container_of(work, struct bonding,
> >+ alb_promisc_disable_work);
> >+ struct alb_bond_info *bond_info = &(BOND_ALB_INFO(bond));
> >+
> >+ /*
> >+ * dev_set_promiscuity requires rtnl and
> >+ * nothing else.
> >+ */
> >+ rtnl_lock();
> >+ dev_set_promiscuity(bond->curr_active_slave->dev, -1);
> >+ bond_info->primary_is_promisc = 0;
> >+ bond_info->rlb_promisc_timeout_counter = 0;
> >+ rtnl_unlock();
> >+}
>
> What prevents this from deadlocking such that cpu A is in
> bond_close, holding RTNL and in cancel_delayed_work_sync, while cpu B is
> in the above function, trying to acquire RTNL?
The main idea of the patch is to move the code (the "commit"
functions) that needs rtnl to another work item. Then
cancel_delayed_work_sync() can be used to cancel the re-arming
work. But you are absolutely right, there is still a deadlock,
since I queue the "commit" work on the same workqueue. So when
cancel_delayed_work_sync() waits for the re-arming work to
finish, it can wait forever because a previously queued "commit"
work is waiting for rtnl.
The solution is to move the "commit" work items to a different
workqueue. Fixed in the new version of the patch below
(bond->wq_rtnl).
> Also, assuming for the moment that the above isn't a problem,
> curr_active_slave may be NULL if the last slave is removed between the
> time bond_alb_promisc_disable is scheduled and when it runs. I'm not
> sure that the alb_bond_info can be guaranteed to be valid, either, if
> the mode changed.
Yes, there may be problems like these, but these are present
already in the current code. Because bond->lock() is released
before rtnl is taken.
Sure, it would be good to deal with these problems, but I don't
think this patch introduces new races like these. They are
already there ... (see below)
> > void bond_alb_monitor(struct work_struct *work)
> > {
> > struct bonding *bond = container_of(work, struct bonding,
> >@@ -1407,10 +1424,6 @@ void bond_alb_monitor(struct work_struct *work)
> >
> > read_lock(&bond->lock);
> >
> >- if (bond->kill_timers) {
> >- goto out;
> >- }
> >-
> > if (bond->slave_cnt == 0) {
> > bond_info->tx_rebalance_counter = 0;
> > bond_info->lp_counter = 0;
> >@@ -1462,25 +1475,11 @@ void bond_alb_monitor(struct work_struct *work)
> > if (bond_info->rlb_enabled) {
> > if (bond_info->primary_is_promisc &&
> > (++bond_info->rlb_promisc_timeout_counter >= RLB_PROMISC_TIMEOUT)) {
> >-
> >- /*
> >- * dev_set_promiscuity requires rtnl and
> >- * nothing else.
> >- */
> >- read_unlock(&bond->lock);
... e.g. here; the current slave may change/disappear, the mode
may change ....
> >- rtnl_lock();
> >-
> >- bond_info->rlb_promisc_timeout_counter = 0;
> >-
I fixed both issues in this new version of the patch.
Signed-off-by: Jiri Bohac <jbohac@...e.cz>
diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c
index 822f586..8015e12 100644
--- a/drivers/net/bonding/bond_3ad.c
+++ b/drivers/net/bonding/bond_3ad.c
@@ -2119,10 +2119,6 @@ void bond_3ad_state_machine_handler(struct work_struct *work)
read_lock(&bond->lock);
- if (bond->kill_timers) {
- goto out;
- }
-
//check if there are any slaves
if (bond->slave_cnt == 0) {
goto re_arm;
@@ -2166,7 +2162,6 @@ void bond_3ad_state_machine_handler(struct work_struct *work)
re_arm:
queue_delayed_work(bond->wq, &bond->ad_work, ad_delta_in_ticks);
-out:
read_unlock(&bond->lock);
}
diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
index c746b33..e4fa3a5 100644
--- a/drivers/net/bonding/bond_alb.c
+++ b/drivers/net/bonding/bond_alb.c
@@ -1397,6 +1397,35 @@ out:
return NETDEV_TX_OK;
}
+void bond_alb_promisc_disable(struct work_struct *work)
+{
+ struct bonding *bond = container_of(work, struct bonding,
+ alb_promisc_disable_work);
+ struct alb_bond_info *bond_info = &(BOND_ALB_INFO(bond));
+
+ /*
+ * dev_set_promiscuity requires rtnl and
+ * nothing else.
+ */
+ rtnl_lock();
+ read_lock(&bond->lock);
+ read_lock(&bond->curr_slave_lock);
+
+ if (!bond_is_lb(bond))
+ goto out;
+ if (!bond->curr_active_slave)
+ goto out;
+
+ dev_set_promiscuity(bond->curr_active_slave->dev, -1);
+ bond_info->primary_is_promisc = 0;
+ bond_info->rlb_promisc_timeout_counter = 0;
+
+out:
+ read_unlock(&bond->curr_slave_lock);
+ read_unlock(&bond->lock);
+ rtnl_unlock();
+}
+
void bond_alb_monitor(struct work_struct *work)
{
struct bonding *bond = container_of(work, struct bonding,
@@ -1407,10 +1436,6 @@ void bond_alb_monitor(struct work_struct *work)
read_lock(&bond->lock);
- if (bond->kill_timers) {
- goto out;
- }
-
if (bond->slave_cnt == 0) {
bond_info->tx_rebalance_counter = 0;
bond_info->lp_counter = 0;
@@ -1462,25 +1487,11 @@ void bond_alb_monitor(struct work_struct *work)
if (bond_info->rlb_enabled) {
if (bond_info->primary_is_promisc &&
(++bond_info->rlb_promisc_timeout_counter >= RLB_PROMISC_TIMEOUT)) {
-
- /*
- * dev_set_promiscuity requires rtnl and
- * nothing else.
- */
- read_unlock(&bond->lock);
- rtnl_lock();
-
- bond_info->rlb_promisc_timeout_counter = 0;
-
/* If the primary was set to promiscuous mode
* because a slave was disabled then
* it can now leave promiscuous mode.
*/
- dev_set_promiscuity(bond->curr_active_slave->dev, -1);
- bond_info->primary_is_promisc = 0;
-
- rtnl_unlock();
- read_lock(&bond->lock);
+ queue_work(bond->wq_rtnl, &bond->alb_promisc_disable_work);
}
if (bond_info->rlb_rebalance) {
@@ -1505,7 +1516,6 @@ void bond_alb_monitor(struct work_struct *work)
re_arm:
queue_delayed_work(bond->wq, &bond->alb_work, alb_delta_in_ticks);
-out:
read_unlock(&bond->lock);
}
diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 2cc4cfc..aae2864 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -2343,10 +2343,15 @@ static int bond_miimon_inspect(struct bonding *bond)
return commit;
}
-static void bond_miimon_commit(struct bonding *bond)
+static void bond_miimon_commit(struct work_struct *work)
{
struct slave *slave;
int i;
+ struct bonding *bond = container_of(work, struct bonding,
+ miimon_commit_work);
+
+ rtnl_lock();
+ read_lock(&bond->lock);
bond_for_each_slave(bond, slave, i) {
switch (slave->new_link) {
@@ -2421,15 +2426,18 @@ static void bond_miimon_commit(struct bonding *bond)
}
do_failover:
- ASSERT_RTNL();
write_lock_bh(&bond->curr_slave_lock);
bond_select_active_slave(bond);
write_unlock_bh(&bond->curr_slave_lock);
}
bond_set_carrier(bond);
+
+ read_unlock(&bond->lock);
+ rtnl_unlock();
}
+
/*
* bond_mii_monitor
*
@@ -2438,14 +2446,13 @@ do_failover:
* an acquisition of appropriate locks followed by a commit phase to
* implement whatever link state changes are indicated.
*/
+
void bond_mii_monitor(struct work_struct *work)
{
struct bonding *bond = container_of(work, struct bonding,
mii_work.work);
read_lock(&bond->lock);
- if (bond->kill_timers)
- goto out;
if (bond->slave_cnt == 0)
goto re_arm;
@@ -2462,23 +2469,14 @@ void bond_mii_monitor(struct work_struct *work)
read_unlock(&bond->curr_slave_lock);
}
- if (bond_miimon_inspect(bond)) {
- read_unlock(&bond->lock);
- rtnl_lock();
- read_lock(&bond->lock);
+ if (bond_miimon_inspect(bond))
+ queue_work(bond->wq_rtnl, &bond->miimon_commit_work);
- bond_miimon_commit(bond);
-
- read_unlock(&bond->lock);
- rtnl_unlock(); /* might sleep, hold no other locks */
- read_lock(&bond->lock);
- }
re_arm:
if (bond->params.miimon)
queue_delayed_work(bond->wq, &bond->mii_work,
msecs_to_jiffies(bond->params.miimon));
-out:
read_unlock(&bond->lock);
}
@@ -2778,9 +2776,6 @@ void bond_loadbalance_arp_mon(struct work_struct *work)
delta_in_ticks = msecs_to_jiffies(bond->params.arp_interval);
- if (bond->kill_timers)
- goto out;
-
if (bond->slave_cnt == 0)
goto re_arm;
@@ -2867,7 +2862,6 @@ void bond_loadbalance_arp_mon(struct work_struct *work)
re_arm:
if (bond->params.arp_interval)
queue_delayed_work(bond->wq, &bond->arp_work, delta_in_ticks);
-out:
read_unlock(&bond->lock);
}
@@ -2949,13 +2943,19 @@ static int bond_ab_arp_inspect(struct bonding *bond, int delta_in_ticks)
/*
* Called to commit link state changes noted by inspection step of
* active-backup mode ARP monitor.
- *
- * Called with RTNL and bond->lock for read.
*/
-static void bond_ab_arp_commit(struct bonding *bond, int delta_in_ticks)
+static void bond_ab_arp_commit(struct work_struct *work)
{
struct slave *slave;
int i;
+ int delta_in_ticks;
+ struct bonding *bond = container_of(work, struct bonding,
+ ab_arp_commit_work);
+
+ rtnl_lock();
+ read_lock(&bond->lock);
+
+ delta_in_ticks = msecs_to_jiffies(bond->params.arp_interval);
bond_for_each_slave(bond, slave, i) {
switch (slave->new_link) {
@@ -3014,6 +3014,9 @@ do_failover:
}
bond_set_carrier(bond);
+
+ read_unlock(&bond->lock);
+ rtnl_unlock();
}
/*
@@ -3093,9 +3096,6 @@ void bond_activebackup_arp_mon(struct work_struct *work)
read_lock(&bond->lock);
- if (bond->kill_timers)
- goto out;
-
delta_in_ticks = msecs_to_jiffies(bond->params.arp_interval);
if (bond->slave_cnt == 0)
@@ -3113,24 +3113,15 @@ void bond_activebackup_arp_mon(struct work_struct *work)
read_unlock(&bond->curr_slave_lock);
}
- if (bond_ab_arp_inspect(bond, delta_in_ticks)) {
- read_unlock(&bond->lock);
- rtnl_lock();
- read_lock(&bond->lock);
+ if (bond_ab_arp_inspect(bond, delta_in_ticks))
+ queue_work(bond->wq_rtnl, &bond->ab_arp_commit_work);
- bond_ab_arp_commit(bond, delta_in_ticks);
-
- read_unlock(&bond->lock);
- rtnl_unlock();
- read_lock(&bond->lock);
- }
bond_ab_arp_probe(bond);
re_arm:
if (bond->params.arp_interval)
queue_delayed_work(bond->wq, &bond->arp_work, delta_in_ticks);
-out:
read_unlock(&bond->lock);
}
@@ -3720,8 +3711,6 @@ static int bond_open(struct net_device *bond_dev)
{
struct bonding *bond = netdev_priv(bond_dev);
- bond->kill_timers = 0;
-
if (bond_is_lb(bond)) {
/* bond_alb_initialize must be called before the timer
* is started.
@@ -3781,26 +3770,23 @@ static int bond_close(struct net_device *bond_dev)
bond->send_grat_arp = 0;
bond->send_unsol_na = 0;
- /* signal timers not to re-arm */
- bond->kill_timers = 1;
-
write_unlock_bh(&bond->lock);
if (bond->params.miimon) { /* link check interval, in milliseconds. */
- cancel_delayed_work(&bond->mii_work);
+ cancel_delayed_work_sync(&bond->mii_work);
}
if (bond->params.arp_interval) { /* arp interval, in milliseconds. */
- cancel_delayed_work(&bond->arp_work);
+ cancel_delayed_work_sync(&bond->arp_work);
}
switch (bond->params.mode) {
case BOND_MODE_8023AD:
- cancel_delayed_work(&bond->ad_work);
+ cancel_delayed_work_sync(&bond->ad_work);
break;
case BOND_MODE_TLB:
case BOND_MODE_ALB:
- cancel_delayed_work(&bond->alb_work);
+ cancel_delayed_work_sync(&bond->alb_work);
break;
default:
break;
@@ -4601,6 +4587,8 @@ static void bond_destructor(struct net_device *bond_dev)
struct bonding *bond = netdev_priv(bond_dev);
if (bond->wq)
destroy_workqueue(bond->wq);
+ if (bond->wq_rtnl)
+ destroy_workqueue(bond->wq_rtnl);
free_netdev(bond_dev);
}
@@ -4660,23 +4648,19 @@ static void bond_setup(struct net_device *bond_dev)
static void bond_work_cancel_all(struct bonding *bond)
{
- write_lock_bh(&bond->lock);
- bond->kill_timers = 1;
- write_unlock_bh(&bond->lock);
-
if (bond->params.miimon && delayed_work_pending(&bond->mii_work))
- cancel_delayed_work(&bond->mii_work);
+ cancel_delayed_work_sync(&bond->mii_work);
if (bond->params.arp_interval && delayed_work_pending(&bond->arp_work))
- cancel_delayed_work(&bond->arp_work);
+ cancel_delayed_work_sync(&bond->arp_work);
if (bond->params.mode == BOND_MODE_ALB &&
delayed_work_pending(&bond->alb_work))
- cancel_delayed_work(&bond->alb_work);
+ cancel_delayed_work_sync(&bond->alb_work);
if (bond->params.mode == BOND_MODE_8023AD &&
delayed_work_pending(&bond->ad_work))
- cancel_delayed_work(&bond->ad_work);
+ cancel_delayed_work_sync(&bond->ad_work);
}
/*
@@ -5083,6 +5067,12 @@ static int bond_init(struct net_device *bond_dev)
bond->wq = create_singlethread_workqueue(bond_dev->name);
if (!bond->wq)
return -ENOMEM;
+ bond->wq_rtnl = create_singlethread_workqueue(bond_dev->name);
+ if (!bond->wq_rtnl) {
+ destroy_workqueue(bond->wq);
+ bond->wq = NULL;
+ return -ENOMEM;
+ }
bond_set_lockdep_class(bond_dev);
@@ -5094,6 +5084,9 @@ static int bond_init(struct net_device *bond_dev)
bond_prepare_sysfs_group(bond);
__hw_addr_init(&bond->mc_list);
+ INIT_WORK(&bond->miimon_commit_work, bond_miimon_commit);
+ INIT_WORK(&bond->ab_arp_commit_work, bond_ab_arp_commit);
+ INIT_WORK(&bond->alb_promisc_disable_work, bond_alb_promisc_disable);
return 0;
}
diff --git a/drivers/net/bonding/bonding.h b/drivers/net/bonding/bonding.h
index c6fdd85..43ba807 100644
--- a/drivers/net/bonding/bonding.h
+++ b/drivers/net/bonding/bonding.h
@@ -198,7 +198,6 @@ struct bonding {
s32 slave_cnt; /* never change this value outside the attach/detach wrappers */
rwlock_t lock;
rwlock_t curr_slave_lock;
- s8 kill_timers;
s8 send_grat_arp;
s8 send_unsol_na;
s8 setup_by_slave;
@@ -219,10 +218,14 @@ struct bonding {
struct vlan_group *vlgrp;
struct packet_type arp_mon_pt;
struct workqueue_struct *wq;
+ struct workqueue_struct *wq_rtnl;
struct delayed_work mii_work;
struct delayed_work arp_work;
struct delayed_work alb_work;
struct delayed_work ad_work;
+ struct work_struct miimon_commit_work;
+ struct work_struct ab_arp_commit_work;
+ struct work_struct alb_promisc_disable_work;
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
struct in6_addr master_ipv6;
#endif
@@ -348,6 +351,7 @@ void bond_select_active_slave(struct bonding *bond);
void bond_change_active_slave(struct bonding *bond, struct slave *new_active);
void bond_register_arp(struct bonding *);
void bond_unregister_arp(struct bonding *);
+void bond_alb_promisc_disable(struct work_struct *work);
struct bond_net {
struct net * net; /* Associated network namespace */
--
Jiri Bohac <jbohac@...e.cz>
SUSE Labs, SUSE CZ
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