netdev - Re: [PATCH net-next 6/9] bonding: use RTNL instead of bond lock for bond_3ad_state_machine

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Message-ID: <527AD5BC.7040907@cogentembedded.com>
Date:	Thu, 07 Nov 2013 02:50:20 +0300
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Ding Tianhong <dingtianhong@...wei.com>,
	Jay Vosburgh <fubar@...ibm.com>,
	Andy Gospodarek <andy@...yhouse.net>,
	"David S. Miller" <davem@...emloft.net>,
	Nikolay Aleksandrov <nikolay@...hat.com>,
	Veaceslav Falico <vfalico@...hat.com>,
	Netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 6/9] bonding: use RTNL instead of bond lock for
 bond_3ad_state_machine_handler()

Hello.

On 11/06/2013 09:53 AM, Ding Tianhong wrote:

> The bond_3ad_state_machine_handler() is a slow path, it use the bond
> lock to protect the bond slave list and slave port, the slave list
> could not be protect by bond lock anymore, so I need to use RTNL or
> RCU instead of bond lock, but if I remove the bond lock, the
> bond_3ad_state_machine_handler() may use the slave port when bond
> releasing the slave, it will occur problems.

> As the bond_3ad_unbind_slave() only protected by bond lock or RTNL,
> so add RCU is not a good solution as it could not protect the slave
> port, so RTNL is fit here.

> Signed-off-by: Ding Tianhong <dingtianhong@...wei.com>
> ---
>   drivers/net/bonding/bond_3ad.c | 15 +++++++--------
>   1 file changed, 7 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c
> index 187b1b7..a4d190e 100644
> --- a/drivers/net/bonding/bond_3ad.c
> +++ b/drivers/net/bonding/bond_3ad.c
> @@ -2068,18 +2068,19 @@ void bond_3ad_state_machine_handler(struct work_struct *work)
[...]
> -	//check if there are any slaves
>   	if (!bond_has_slaves(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);
>   		port = slave ? &(SLAVE_AD_INFO(slave).port) : NULL;
>
> -		// select the active aggregator for the bond
>   		if (port) {
>   			if (!port->slave) {
>   				pr_warning("%s: Warning: bond's first port is uninitialized\n",
> @@ -2093,7 +2094,6 @@ 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) {
>   		port = &(SLAVE_AD_INFO(slave).port);
>   		if (!port->slave) {
> @@ -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;
>

    These comment changes are not documented in the changelog and should most 
probably be in a separate patch.

WBR, Sergei

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