netdev - Re: [RFC PATCH V4 02/13] netback: add module unload function.

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Date:	Thu, 02 Feb 2012 18:08:44 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Wei Liu <wei.liu2@...rix.com>
Cc:	netdev@...r.kernel.org, xen-devel@...ts.xensource.com,
	ian.campbell@...rix.com, konrad.wilk@...cle.com
Subject: Re: [RFC PATCH V4 02/13] netback: add module unload function.

Le jeudi 02 février 2012 à 16:49 +0000, Wei Liu a écrit :
> Enables users to unload netback module.
> 
> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> Tested-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> Signed-off-by: Wei Liu <wei.liu2@...rix.com>
> ---
>  drivers/net/xen-netback/common.h  |    1 +
>  drivers/net/xen-netback/netback.c |   14 ++++++++++++++
>  drivers/net/xen-netback/xenbus.c  |    5 +++++
>  3 files changed, 20 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
> index 288b2f3..372c7f5 100644
> --- a/drivers/net/xen-netback/common.h
> +++ b/drivers/net/xen-netback/common.h
> @@ -126,6 +126,7 @@ void xenvif_get(struct xenvif *vif);
>  void xenvif_put(struct xenvif *vif);
>  
>  int xenvif_xenbus_init(void);
> +void xenvif_xenbus_exit(void);
>  
>  int xenvif_schedulable(struct xenvif *vif);
>  
> diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
> index d11205f..3059684 100644
> --- a/drivers/net/xen-netback/netback.c
> +++ b/drivers/net/xen-netback/netback.c
> @@ -1670,5 +1670,19 @@ failed_init:
>  
>  module_init(netback_init);
>  

While reviewing this code, I can see current netback_init() is buggy.

It assumes all online cpus xen_netbk_group_nr are numbered from 0 to
xen_netbk_group_nr-1

This is not right.

Instead of using :

xen_netbk = vzalloc(sizeof(struct xen_netbk) * xen_netbk_group_nr);

You should use a percpu variable to get proper NUMA properties.

And instead of looping like :

for (group = 0; group < xen_netbk_group_nr; group++) {

You must use :

for_each_online_cpu(cpu) {
	...
}

[ and also use kthread_create_on_node() instead of kthread_create() ]



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