netdev - Re: [PATCH v2 net 5/6] net: mvneta: The mvneta_percpu

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Date:	Mon, 1 Feb 2016 16:33:44 +0300
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Gregory CLEMENT <gregory.clement@...e-electrons.com>,
	"David S. Miller" <davem@...emloft.net>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
Cc:	Jason Cooper <jason@...edaemon.net>, Andrew Lunn <andrew@...n.ch>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	linux-arm-kernel@...ts.infradead.org,
	Lior Amsalem <alior@...vell.com>,
	Nadav Haklai <nadavh@...vell.com>,
	Marcin Wojtas <mw@...ihalf.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Willy Tarreau <w@....eu>
Subject: Re: [PATCH v2 net 5/6] net: mvneta: The mvneta_percpu_elect function
 should be atomic

On 2/1/2016 4:07 PM, Gregory CLEMENT wrote:

> 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.
>
> During the loop of mvneta_percpu_elect we associates the queues to the
> CPUs, if there is a topology change during this loop, then the mapping
> between the CPUs and the queues could be wrong. During this loop the
> interrupt mask is also updating for each CPUs, It should not be changed
> in the same time by other part of the driver.
>
> This patch adds spinlock to create the needed critical sections.
>
> Signed-off-by: Gregory CLEMENT <gregory.clement@...e-electrons.com>
> ---
>   drivers/net/ethernet/marvell/mvneta.c | 15 +++++++++++++++
>   1 file changed, 15 insertions(+)
>
> diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
> index 1ed813d478e8..4d40d2fde7ca 100644
> --- a/drivers/net/ethernet/marvell/mvneta.c
> +++ b/drivers/net/ethernet/marvell/mvneta.c
[...]
> @@ -2855,6 +2859,11 @@ static void mvneta_percpu_elect(struct mvneta_port *pp)
>   {
>   	int online_cpu_idx, max_cpu, cpu, i = 0;
>
> +	/* Electing a CPU must done in an atomic way: it should be

    Must be done.

> +	 * done after or before the removal/insertion of a CPU and
> +	 * this function is not reentrant.
> +	 */
> +	spin_lock(&pp->lock);
>   	online_cpu_idx = pp->rxq_def % num_online_cpus();
>   	max_cpu = num_present_cpus();
>
[...]

MBR, Sergei