netdev - Re: [PATCH] bonding: avoid repeated display of same link status change

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Date:   Mon, 17 Sep 2018 07:38:02 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     mk.singh@...cle.com, netdev@...r.kernel.org
Cc:     Jay Vosburgh <j.vosburgh@...il.com>,
        Veaceslav Falico <vfalico@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>,
        "David S. Miller" <davem@...emloft.net>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] bonding: avoid repeated display of same link status
 change



On 09/17/2018 12:20 AM, mk.singh@...cle.com wrote:
> From: Manish Kumar Singh <mk.singh@...cle.com>
> 
> When link status change needs to be committed and rtnl lock couldn't be
> taken, avoid redisplay of same link status change message.
> 
> Signed-off-by: Manish Kumar Singh <mk.singh@...cle.com>
> ---
>  drivers/net/bonding/bond_main.c | 6 ++++--
>  include/net/bonding.h           | 1 +
>  2 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index 217b790d22ed..fb4e3aff1677 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -2087,7 +2087,7 @@ static int bond_miimon_inspect(struct bonding *bond)
>  			bond_propose_link_state(slave, BOND_LINK_FAIL);
>  			commit++;
>  			slave->delay = bond->params.downdelay;
> -			if (slave->delay) {
> +			if (slave->delay && !bond->rtnl_needed) {
>  				netdev_info(bond->dev, "link status down for %sinterface %s, disabling it in %d ms\n",
>  					    (BOND_MODE(bond) ==
>  					     BOND_MODE_ACTIVEBACKUP) ?
> @@ -2127,7 +2127,7 @@ static int bond_miimon_inspect(struct bonding *bond)
>  			commit++;
>  			slave->delay = bond->params.updelay;
>  
> -			if (slave->delay) {
> +			if (slave->delay && !bond->rtnl_needed) {
>  				netdev_info(bond->dev, "link status up for interface %s, enabling it in %d ms\n",
>  					    slave->dev->name,
>  					    ignore_updelay ? 0 :
> @@ -2301,9 +2301,11 @@ static void bond_mii_monitor(struct work_struct *work)
>  		if (!rtnl_trylock()) {
>  			delay = 1;
>  			should_notify_peers = false;
> +			bond->rtnl_needed = true;

How can you set a shared variable with no synchronization ?

A bool is particularly dangerous here, at least on some arches.

>  			goto re_arm;
>  		}
>  
> +		bond->rtnl_needed = false;
>  		bond_for_each_slave(bond, slave, iter) {
>  			bond_commit_link_state(slave, BOND_SLAVE_NOTIFY_LATER);
>  		}
> diff --git a/include/net/bonding.h b/include/net/bonding.h
> index 808f1d167349..50d61cf77855 100644
> --- a/include/net/bonding.h
> +++ b/include/net/bonding.h
> @@ -234,6 +234,7 @@ struct bonding {
>  	struct	 dentry *debug_dir;
>  #endif /* CONFIG_DEBUG_FS */
>  	struct rtnl_link_stats64 bond_stats;
> +	bool rtnl_needed;
>  };
>  
>  #define bond_slave_get_rcu(dev) \
>