netdev - Re: [PATCH 6/6] net: mvneta: Statically assign queues to CPUs

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Message-ID: <20150703164624.77188a63@free-electrons.com>
Date:	Fri, 3 Jul 2015 16:46:24 +0200
From:	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
To:	Maxime Ripard <maxime.ripard@...e-electrons.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Gregory Clement <gregory.clement@...e-electrons.com>,
	Jason Cooper <jason@...edaemon.net>,
	Andrew Lunn <andrew@...n.ch>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH 6/6] net: mvneta: Statically assign queues to CPUs

Maxime,

On Fri,  3 Jul 2015 16:25:51 +0200, Maxime Ripard wrote:

> +static void mvneta_percpu_enable(void *arg)
> +{
> +	struct mvneta_port *pp = arg;
> +
> +	enable_percpu_irq(pp->dev->irq, IRQ_TYPE_NONE);
> +}
> +
>  static int mvneta_open(struct net_device *dev)
>  {
>  	struct mvneta_port *pp = netdev_priv(dev);
> @@ -2655,6 +2662,19 @@ static int mvneta_open(struct net_device *dev)
>  		goto err_cleanup_txqs;
>  	}
>  
> +	/*
> +	 * Even though the documentation says that request_percpu_irq
> +	 * doesn't enable the interrupts automatically, it actually
> +	 * does so on the local CPU.
> +	 *
> +	 * Make sure it's disabled.
> +	 */
> +	disable_percpu_irq(pp->dev->irq);
> +
> +	/* Enable per-CPU interrupt on the one CPU we care about */
> +	smp_call_function_single(rxq_def % num_online_cpus(),
> +				 mvneta_percpu_enable, pp, true);

What happens if that CPU goes offline through CPU hotplug?

Thanks!

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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