netdev - Re: [patch net-next v3 11/12] mlxsw: spectrum_router: Request a dump of FIB tables during init

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Date:   Wed, 30 Nov 2016 16:37:48 +0100
From:   Hannes Frederic Sowa <hannes@...essinduktion.org>
To:     Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org
Cc:     davem@...emloft.net, idosch@...lanox.com, eladr@...lanox.com,
        yotamg@...lanox.com, nogahf@...lanox.com, arkadis@...lanox.com,
        ogerlitz@...lanox.com, roopa@...ulusnetworks.com,
        dsa@...ulusnetworks.com, nikolay@...ulusnetworks.com,
        andy@...yhouse.net, vivien.didelot@...oirfairelinux.com,
        andrew@...n.ch, f.fainelli@...il.com, alexander.h.duyck@...el.com,
        kaber@...sh.net
Subject: Re: [patch net-next v3 11/12] mlxsw: spectrum_router: Request a dump
 of FIB tables during init

On 30.11.2016 11:09, Jiri Pirko wrote:
> From: Ido Schimmel <idosch@...lanox.com>
> 
> Make sure the device has a complete view of the FIB tables by invoking
> their dump during module init.
> 
> Signed-off-by: Ido Schimmel <idosch@...lanox.com>
> Signed-off-by: Jiri Pirko <jiri@...lanox.com>
> ---
>  .../net/ethernet/mellanox/mlxsw/spectrum_router.c  | 23 ++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
> index 14bed1d..d176047 100644
> --- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
> +++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
> @@ -2027,8 +2027,23 @@ static int mlxsw_sp_router_fib_event(struct notifier_block *nb,
>  	return NOTIFY_DONE;
>  }
>  
> +static void mlxsw_sp_router_fib_dump_flush(struct notifier_block *nb)
> +{
> +	struct mlxsw_sp *mlxsw_sp = container_of(nb, struct mlxsw_sp, fib_nb);
> +
> +	/* Flush pending FIB notifications and then flush the device's
> +	 * table before requesting another dump. Do that with RTNL held,
> +	 * as FIB notification block is already registered.
> +	 */
> +	mlxsw_core_flush_owq();
> +	rtnl_lock();
> +	mlxsw_sp_router_fib_flush(mlxsw_sp);
> +	rtnl_unlock();
> +}
> +
>  int mlxsw_sp_router_init(struct mlxsw_sp *mlxsw_sp)
>  {
> +	fib_dump_cb_t *cb = mlxsw_sp_router_fib_dump_flush;
>  	int err;
>  
>  	INIT_LIST_HEAD(&mlxsw_sp->router.nexthop_neighs_list);
> @@ -2048,8 +2063,16 @@ int mlxsw_sp_router_init(struct mlxsw_sp *mlxsw_sp)
>  
>  	mlxsw_sp->fib_nb.notifier_call = mlxsw_sp_router_fib_event;
>  	register_fib_notifier(&mlxsw_sp->fib_nb);

Sorry to pick in here again:

There is a race here. You need to protect the registration of the fib
notifier as well by the sequence counter. Updates here are not ordered
in relation to this code below.

I think just move the register notification into the fib_notifier_dump
function, rename it to fib_notifier_init and use it here:

> +	if (!fib_notifier_dump(&mlxsw_sp->fib_nb, &init_net, cb)) {
> +		err = -EBUSY;
> +		goto err_fib_notifier_dump;
> +	}
> +
>  	return 0;

Thanks,
Hannes