netdev - Re: [PATCH net-next v2 7/10] bonding: rebuild the lock use for bond_3ad_state_machine

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Date:	Fri, 08 Nov 2013 16:43:14 +0100
From:	Nikolay Aleksandrov <nikolay@...hat.com>
To:	Ding Tianhong <dingtianhong@...wei.com>
CC:	Jay Vosburgh <fubar@...ibm.com>,
	Andy Gospodarek <andy@...yhouse.net>,
	"David S. Miller" <davem@...emloft.net>,
	Veaceslav Falico <vfalico@...hat.com>,
	Netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next v2 7/10] bonding: rebuild the lock use for bond_3ad_state_machine_handler()

On 11/08/2013 03:08 AM, Ding Tianhong wrote:
> The bond_3ad_state_machine_handler() use the bond lock to protect
> the bond slave list and slave port, so as the before patch said,
> I remove bond lock and replace with RCU.
> 
> The nots in the function is still too old, clean up the nots.
> 
> Suggested-by: Jay Vosburgh <fubar@...ibm.com>
> Suggested-by: Veaceslav Falico <vfalico@...hat.com>
> Signed-off-by: Ding Tianhong <dingtianhong@...wei.com>
> ---
>  drivers/net/bonding/bond_3ad.c | 21 ++++++++++-----------
>  1 file changed, 10 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c
> index 187b1b7..09edccf61 100644
> --- a/drivers/net/bonding/bond_3ad.c
> +++ b/drivers/net/bonding/bond_3ad.c
> @@ -2068,18 +2068,18 @@ void bond_3ad_state_machine_handler(struct work_struct *work)
>  	struct slave *slave;
>  	struct port *port;
>  
> -	read_lock(&bond->lock);
> +	rcu_read_lock();
>  
> -	//check if there are any slaves
> -	if (!bond_has_slaves(bond))
> +	/* check if there are any slaves */
> +	if (!bond_has_slaves_rcu(bond))
>  		goto re_arm;
>  
> -	// check if agg_select_timer timer after initialize is timed out
> +	/* check if agg_select_timer timer after initialize is timed out */
>  	if (BOND_AD_INFO(bond).agg_select_timer && !(--BOND_AD_INFO(bond).agg_select_timer)) {
> -		slave = bond_first_slave(bond);
> +		slave = bond_first_slave_rcu(bond);
>  		port = slave ? &(SLAVE_AD_INFO(slave).port) : NULL;
>  
> -		// select the active aggregator for the bond
> +		/* select the active aggregator for the bond */
>  		if (port) {
>  			if (!port->slave) {
>  				pr_warning("%s: Warning: bond's first port is uninitialized\n",
This continues to execute:
aggregator = __get_first_agg(port);
ad_agg_selection_logic(aggregator)
And neither ad_agg_selection_logic nor __get_first_agg are RCU-safe.

> @@ -2093,8 +2093,8 @@ void bond_3ad_state_machine_handler(struct work_struct *work)
>  		bond_3ad_set_carrier(bond);
>  	}
>  
> -	// for each port run the state machines
> -	bond_for_each_slave(bond, slave, iter) {
> +	/* for each port run the state machines */
> +	bond_for_each_slave_rcu(bond, slave, iter) {
>  		port = &(SLAVE_AD_INFO(slave).port);
>  		if (!port->slave) {
>  			pr_warning("%s: Warning: Found an uninitialized port\n",
> @@ -2114,7 +2114,7 @@ void bond_3ad_state_machine_handler(struct work_struct *work)
>  		ad_mux_machine(port);
>  		ad_tx_machine(port);
>  
> -		// turn off the BEGIN bit, since we already handled it
> +		/* turn off the BEGIN bit, since we already handled it */
>  		if (port->sm_vars & AD_PORT_BEGIN)
>  			port->sm_vars &= ~AD_PORT_BEGIN;
>  
> @@ -2122,9 +2122,8 @@ void bond_3ad_state_machine_handler(struct work_struct *work)
>  	}
>  
>  re_arm:
> +	rcu_read_unlock();
>  	queue_delayed_work(bond->wq, &bond->ad_work, ad_delta_in_ticks);
> -
> -	read_unlock(&bond->lock);
>  }
>  
>  /**
> 

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