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

[David Vrabel <david.vrabel@xxxxxxxxxx>]

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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