Subject: Re: [RFC PATCH v4 12/13] memory-hotplug : add node_device_release

From: Wen Congyang <[email-masked]>
Date: Fri, 27 Jul 2012 14:17:19 +0800

At 07/18/2012 06:17 PM, Yasuaki Ishimatsu Wrote:
> When calling unregister_node(), the function shows following message at
> device_release().
> 
> Device 'node2' does not have a release() function, it is broken and must be
> fixed.
> 
> So the patch implements node_device_release()
> 
> CC: David Rientjes <[email-masked]>
> CC: Jiang Liu <[email-masked]>
> CC: Len Brown <[email-masked]>
> CC: Benjamin Herrenschmidt <[email-masked]>
> CC: Paul Mackerras <[email-masked]> 
> CC: Christoph Lameter <[email-masked]>
> Cc: Minchan Kim <[email-masked]>
> CC: Andrew Morton <[email-masked]>
> CC: KOSAKI Motohiro <[email-masked]> 
> CC: Wen Congyang <[email-masked]>
> Signed-off-by: Yasuaki Ishimatsu <[email-masked]>
> 
> ---
>  drivers/base/node.c |    7 +++++++
>  1 file changed, 7 insertions(+)
> 
> Index: linux-3.5-rc6/drivers/base/node.c
> ===================================================================
> --- linux-3.5-rc6.orig/drivers/base/node.c	2012-07-18 18:24:29.191121066 +0900
> +++ linux-3.5-rc6/drivers/base/node.c	2012-07-18 18:25:47.111146983 +0900
> @@ -252,6 +252,12 @@ static inline void hugetlb_register_node
>  static inline void hugetlb_unregister_node(struct node *node) {}
>  #endif
>  
> +static void node_device_release(struct device *dev)
> +{
> +	struct node *node_dev = to_node(dev);
> +
> +	memset(node_dev, 0, sizeof(struct node));

This line is wrong. node_dev->work_struct may be queued in workqueue.
So, it is very dangerous to clear node_dev->work_struct here.
In my test, it will cause kernel panicked.

Thanks
Wen Congyang
> +}
>  
>  /*
>   * register_node - Setup a sysfs device for a node.
> @@ -265,6 +271,7 @@ int register_node(struct node *node, int
>  
>  	node->dev.id = num;
>  	node->dev.bus = &node_subsys;
> +	node->dev.release = node_device_release;
>  	error = device_register(&node->dev);
>  
>  	if (!error){
> 
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