Re: [PATCH] net: mvneta: fix changing MTU when using per-cpu processing

[David Miller]

From: Marcin Wojtas 
Date: Fri,  1 Apr 2016 15:21:18 +0200

> After enabling per-cpu processing it appeared that under heavy load
> changing MTU can result in blocking all port's interrupts and transmitting
> data is not possible after the change.
> 
> This commit fixes above issue by disabling percpu interrupts for the
> time, when TXQs and RXQs are reconfigured.
> 
> Signed-off-by: Marcin Wojtas 

Applied, thanks.

When I reviewed this I was worried that this was yet another case where
the ndo op could be invoked in a potentially atomic or similar context,
whereby on_each_cpu() would be illegal to use.

But that appears to not be the case, and thus this change is just fine.

Thanks.

Re: [PATCH] net: mvneta: fix changing MTU when using per-cpu processing

[Marcin Wojtas]

Hi David,

I've just realized I forgot to add an information, that this patch is
intended for 'net' tree.

Best regards,
Marcin

2016-04-01 15:21 GMT+02:00 Marcin Wojtas :
> After enabling per-cpu processing it appeared that under heavy load
> changing MTU can result in blocking all port's interrupts and transmitting
> data is not possible after the change.
>
> This commit fixes above issue by disabling percpu interrupts for the
> time, when TXQs and RXQs are reconfigured.
>
> Signed-off-by: Marcin Wojtas 
> ---
>  drivers/net/ethernet/marvell/mvneta.c | 30 --
>  1 file changed, 16 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/net/ethernet/marvell/mvneta.c 
> b/drivers/net/ethernet/marvell/mvneta.c
> index fee6a91..a433de9 100644
> --- a/drivers/net/ethernet/marvell/mvneta.c
> +++ b/drivers/net/ethernet/marvell/mvneta.c
> @@ -3083,6 +3083,20 @@ static int mvneta_check_mtu_valid(struct net_device 
> *dev, int mtu)
> return mtu;
>  }
>
> +static void mvneta_percpu_enable(void *arg)
> +{
> +   struct mvneta_port *pp = arg;
> +
> +   enable_percpu_irq(pp->dev->irq, IRQ_TYPE_NONE);
> +}
> +
> +static void mvneta_percpu_disable(void *arg)
> +{
> +   struct mvneta_port *pp = arg;
> +
> +   disable_percpu_irq(pp->dev->irq);
> +}
> +
>  /* Change the device mtu */
>  static int mvneta_change_mtu(struct net_device *dev, int mtu)
>  {
> @@ -3107,6 +3121,7 @@ static int mvneta_change_mtu(struct net_device *dev, 
> int mtu)
>  * reallocation of the queues
>  */
> mvneta_stop_dev(pp);
> +   on_each_cpu(mvneta_percpu_disable, pp, true);
>
> mvneta_cleanup_txqs(pp);
> mvneta_cleanup_rxqs(pp);
> @@ -3130,6 +3145,7 @@ static int mvneta_change_mtu(struct net_device *dev, 
> int mtu)
> return ret;
> }
>
> +   on_each_cpu(mvneta_percpu_enable, pp, true);
> mvneta_start_dev(pp);
> mvneta_port_up(pp);
>
> @@ -3283,20 +3299,6 @@ static void mvneta_mdio_remove(struct mvneta_port *pp)
> pp->phy_dev = NULL;
>  }
>
> -static void mvneta_percpu_enable(void *arg)
> -{
> -   struct mvneta_port *pp = arg;
> -
> -   enable_percpu_irq(pp->dev->irq, IRQ_TYPE_NONE);
> -}
> -
> -static void mvneta_percpu_disable(void *arg)
> -{
> -   struct mvneta_port *pp = arg;
> -
> -   disable_percpu_irq(pp->dev->irq);
> -}
> -
>  /* Electing a CPU must be done in an atomic way: it should be done
>   * after or before the removal/insertion of a CPU and this function is
>   * not reentrant.
> --
> 1.8.3.1
>