Re: [PATCH v2] memory-hotplug: add automatic onlining policy for the newly added memory

[David Vrabel]

On 22/12/15 16:32, Vitaly Kuznetsov wrote:
> @@ -1292,6 +1304,11 @@ int __ref add_memory_resource(int nid, struct resource *res)
>  	/* create new memmap entry */
>  	firmware_map_add_hotplug(start, start + size, "System RAM");
>  
> +	/* online pages if requested */
> +	if (online)
> +		online_pages(start >> PAGE_SHIFT, size >> PAGE_SHIFT,
> +			     MMOP_ONLINE_KEEP);

This will cause the Xen balloon driver to deadlock because it calls
add_memory_resource() with the balloon_mutex locked and the online page
callback also locks the balloon_mutex.

David
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