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

[Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>]

David Vrabel <david.vrabel@xxxxxxxxxx> writes:

> 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.

Currently xen ballon driver always calls add_memory_resource() with
online=false so this won't happen.

-- 
  Vitaly

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