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Message-ID: <4EAA0ADF.5020504@hitachi.com>
Date: Fri, 28 Oct 2011 10:52:31 +0900
From: HAYASAKA Mitsuo <mitsuo.hayasaka.hu@...achi.com>
To: Jay Vosburgh <fubar@...ibm.com>
Cc: netdev@...r.kernel.org,
Américo Wang <xiyou.wangcong@...il.com>,
Stephen Hemminger <shemminger@...tta.com>,
Andy Gospodarek <andy@...yhouse.net>,
linux-kernel@...r.kernel.org, yrl.pp-manager.tt@...achi.com
Subject: Re: [PATCH net -v2] [BUGFIX] bonding: use flush_delayed_work_sync
in bond_close
Hi Joy,
I checked your patch, and any problems have not been observed for
almost one day although I could reproduce the BUG in the latest net-next
without it.
I think this patch works well.
Tested-by: Mitsuo Hayasaka <mitsuo.hayasaka.hu@...achi.com>
(2011/10/27 2:31), Jay Vosburgh wrote:
> HAYASAKA Mitsuo <mitsuo.hayasaka.hu@...achi.com> wrote:
> [...]
>> The interval of mii_mon was set to 1 to reproduce this bug easily and
>> the 802.3ad mode was used. Then, I executed the following command.
>>
>> # while true; do ifconfig bond0 down; done &
>> # while true; do ifconfig bond0 up; done &
>>
>> This bug rarely occurs since it is the severe timing problem.
>> I found that it is more easily to reproduce this bug when using guest OS.
>>
>> For example, it took one to three days for me to reproduce it on host OS,
>> but some hours on guest OS.
>
> Could you test this patch and see if it resolves the problem?
>
> This patch does a few things:
>
> All of the monitor functions that run on work queues are
> modified to never unconditionally acquire RTNL; all will reschedule the
> work and return if rtnl_trylock fails. This covers bond_mii_monitor,
> bond_activebackup_arp_mon, and bond_alb_monitor.
>
> The "clear out the work queues" calls in bond_close and
> bond_uninit now call cancel_delayed_work_sync, which should either
> delete a pending work item, or wait for an executing item to complete.
> I chose cancel_ over the original patch's flush_ because we just want
> the work queue stopped. We don't need to have any pending items execute
> if they're not already running.
>
> Also in reference to the previous, I'm not sure if we still need
> to check for delayed_work_pending, but I've left those checks in place.
>
> Remove the "kill_timers" field and all references to it. If
> cancel_delayed_work_sync is safe to use, we do not need an extra
> sentinel.
>
> Lastly, for testing purposes only, the bond_alb_monitor in this
> patch includes an unconditional call to rtnl_trylock(); this is an
> artifical way to make the race in that function easier to test for,
> because the real race is very difficult to hit.
>
> This patch is against net-next as of yesterday.
>
> Comments?
>
> -J
>
>
> diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c
> index b33c099..0ae0d7c 100644
> --- a/drivers/net/bonding/bond_3ad.c
> +++ b/drivers/net/bonding/bond_3ad.c
> @@ -2110,9 +2110,6 @@ 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;
> @@ -2161,9 +2158,8 @@ void bond_3ad_state_machine_handler(struct work_struct *work)
> }
>
> re_arm:
> - if (!bond->kill_timers)
> - queue_delayed_work(bond->wq, &bond->ad_work, ad_delta_in_ticks);
> -out:
> + queue_delayed_work(bond->wq, &bond->ad_work, ad_delta_in_ticks);
> +
> read_unlock(&bond->lock);
> }
>
> diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
> index d4fbd2e..13d1bf9 100644
> --- a/drivers/net/bonding/bond_alb.c
> +++ b/drivers/net/bonding/bond_alb.c
> @@ -1343,10 +1343,6 @@ 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;
> @@ -1394,6 +1390,14 @@ void bond_alb_monitor(struct work_struct *work)
> bond_info->tx_rebalance_counter = 0;
> }
>
> + /* XXX - unconditional attempt at RTNL for testing purposes, as
> + * normal case, below, is difficult to induce.
> + */
> + read_unlock(&bond->lock);
> + if (rtnl_trylock())
> + rtnl_unlock();
> + read_lock(&bond->lock);
> +
> /* handle rlb stuff */
> if (bond_info->rlb_enabled) {
> if (bond_info->primary_is_promisc &&
> @@ -1404,7 +1408,10 @@ void bond_alb_monitor(struct work_struct *work)
> * nothing else.
> */
> read_unlock(&bond->lock);
> - rtnl_lock();
> + if (!rtnl_trylock()) {
> + read_lock(&bond->lock);
> + goto re_arm;
> + }
>
> bond_info->rlb_promisc_timeout_counter = 0;
>
> @@ -1440,9 +1447,8 @@ void bond_alb_monitor(struct work_struct *work)
> }
>
> re_arm:
> - if (!bond->kill_timers)
> - queue_delayed_work(bond->wq, &bond->alb_work, alb_delta_in_ticks);
> -out:
> + queue_delayed_work(bond->wq, &bond->alb_work, alb_delta_in_ticks);
> +
> read_unlock(&bond->lock);
> }
>
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index 71efff3..e6fefff 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -774,9 +774,6 @@ static void bond_resend_igmp_join_requests(struct bonding *bond)
>
> read_lock(&bond->lock);
>
> - if (bond->kill_timers)
> - goto out;
> -
> /* rejoin all groups on bond device */
> __bond_resend_igmp_join_requests(bond->dev);
>
> @@ -790,9 +787,9 @@ static void bond_resend_igmp_join_requests(struct bonding *bond)
> __bond_resend_igmp_join_requests(vlan_dev);
> }
>
> - if ((--bond->igmp_retrans > 0) && !bond->kill_timers)
> + if (--bond->igmp_retrans > 0)
> queue_delayed_work(bond->wq, &bond->mcast_work, HZ/5);
> -out:
> +
> read_unlock(&bond->lock);
> }
>
> @@ -2518,19 +2515,26 @@ void bond_mii_monitor(struct work_struct *work)
> struct bonding *bond = container_of(work, struct bonding,
> mii_work.work);
> bool should_notify_peers = false;
> + unsigned long delay;
>
> read_lock(&bond->lock);
> - if (bond->kill_timers)
> - goto out;
> +
> + delay = msecs_to_jiffies(bond->params.miimon);
>
> if (bond->slave_cnt == 0)
> goto re_arm;
>
> - should_notify_peers = bond_should_notify_peers(bond);
> -
> if (bond_miimon_inspect(bond)) {
> read_unlock(&bond->lock);
> - rtnl_lock();
> +
> + /* Race avoidance with bond_close flush of workqueue */
> + if (!rtnl_trylock()) {
> + read_lock(&bond->lock);
> + delay = 1;
> + should_notify_peers = false;
> + goto re_arm;
> + }
> +
> read_lock(&bond->lock);
>
> bond_miimon_commit(bond);
> @@ -2540,15 +2544,21 @@ void bond_mii_monitor(struct work_struct *work)
> read_lock(&bond->lock);
> }
>
> + should_notify_peers = bond_should_notify_peers(bond);
> +
> re_arm:
> - if (bond->params.miimon && !bond->kill_timers)
> - queue_delayed_work(bond->wq, &bond->mii_work,
> - msecs_to_jiffies(bond->params.miimon));
> -out:
> + if (bond->params.miimon)
> + queue_delayed_work(bond->wq, &bond->mii_work, delay);
> +
> read_unlock(&bond->lock);
>
> if (should_notify_peers) {
> - rtnl_lock();
> + if (!rtnl_trylock()) {
> + read_lock(&bond->lock);
> + bond->send_peer_notif++;
> + read_unlock(&bond->lock);
> + return;
> + }
> netdev_bonding_change(bond->dev, NETDEV_NOTIFY_PEERS);
> rtnl_unlock();
> }
> @@ -2790,9 +2800,6 @@ 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;
>
> @@ -2889,9 +2896,9 @@ void bond_loadbalance_arp_mon(struct work_struct *work)
> }
>
> re_arm:
> - if (bond->params.arp_interval && !bond->kill_timers)
> + if (bond->params.arp_interval)
> queue_delayed_work(bond->wq, &bond->arp_work, delta_in_ticks);
> -out:
> +
> read_unlock(&bond->lock);
> }
>
> @@ -3132,9 +3139,6 @@ 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)
> @@ -3144,7 +3148,15 @@ void bond_activebackup_arp_mon(struct work_struct *work)
>
> if (bond_ab_arp_inspect(bond, delta_in_ticks)) {
> read_unlock(&bond->lock);
> - rtnl_lock();
> +
> + /* Race avoidance with bond_close flush of workqueue */
> + if (!rtnl_trylock()) {
> + read_lock(&bond->lock);
> + delta_in_ticks = 1;
> + should_notify_peers = false;
> + goto re_arm;
> + }
> +
> read_lock(&bond->lock);
>
> bond_ab_arp_commit(bond, delta_in_ticks);
> @@ -3157,13 +3169,18 @@ void bond_activebackup_arp_mon(struct work_struct *work)
> bond_ab_arp_probe(bond);
>
> re_arm:
> - if (bond->params.arp_interval && !bond->kill_timers)
> + if (bond->params.arp_interval)
> queue_delayed_work(bond->wq, &bond->arp_work, delta_in_ticks);
> -out:
> +
> read_unlock(&bond->lock);
>
> if (should_notify_peers) {
> - rtnl_lock();
> + if (!rtnl_trylock()) {
> + read_lock(&bond->lock);
> + bond->send_peer_notif++;
> + read_unlock(&bond->lock);
> + return;
> + }
> netdev_bonding_change(bond->dev, NETDEV_NOTIFY_PEERS);
> rtnl_unlock();
> }
> @@ -3425,8 +3442,6 @@ static int bond_open(struct net_device *bond_dev)
> struct slave *slave;
> int i;
>
> - bond->kill_timers = 0;
> -
> /* reset slave->backup and slave->inactive */
> read_lock(&bond->lock);
> if (bond->slave_cnt > 0) {
> @@ -3495,33 +3510,30 @@ static int bond_close(struct net_device *bond_dev)
>
> bond->send_peer_notif = 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;
> }
>
> if (delayed_work_pending(&bond->mcast_work))
> - cancel_delayed_work(&bond->mcast_work);
> + cancel_delayed_work_sync(&bond->mcast_work);
>
> if (bond_is_lb(bond)) {
> /* Must be called only after all
> @@ -4368,26 +4380,22 @@ 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);
>
> if (delayed_work_pending(&bond->mcast_work))
> - cancel_delayed_work(&bond->mcast_work);
> + cancel_delayed_work_sync(&bond->mcast_work);
> }
>
> /*
> diff --git a/drivers/net/bonding/bonding.h b/drivers/net/bonding/bonding.h
> index 82fec5f..1aecc37 100644
> --- a/drivers/net/bonding/bonding.h
> +++ b/drivers/net/bonding/bonding.h
> @@ -222,7 +222,6 @@ struct bonding {
> struct slave *);
> rwlock_t lock;
> rwlock_t curr_slave_lock;
> - s8 kill_timers;
> u8 send_peer_notif;
> s8 setup_by_slave;
> s8 igmp_retrans;
>
>
> ---
> -Jay Vosburgh, IBM Linux Technology Center, fubar@...ibm.com
>
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