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

Started byDavid Vrabel <david.vrabel@citrix.com>
First post2016-01-04 12:30 +0100
Last post2016-01-04 15:30 +0100
Articles 2 — 2 participants

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  Re: [PATCH v2] memory-hotplug: add automatic onlining policy for  the newly added memory David Vrabel <david.vrabel@citrix.com> - 2016-01-04 12:30 +0100
    Re: [PATCH v2] memory-hotplug: add automatic onlining policy for the newly added memory Vitaly Kuznetsov <vkuznets@redhat.com> - 2016-01-04 15:30 +0100

#1300638 — Re: [PATCH v2] memory-hotplug: add automatic onlining policy for the newly added memory

FromDavid Vrabel <david.vrabel@citrix.com>
Date2016-01-04 12:30 +0100
SubjectRe: [PATCH v2] memory-hotplug: add automatic onlining policy for the newly added memory
Message-ID<qNbuN-2MN-1@gated-at.bofh.it>
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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#1300776 — Re: [PATCH v2] memory-hotplug: add automatic onlining policy for the newly added memory

FromVitaly Kuznetsov <vkuznets@redhat.com>
Date2016-01-04 15:30 +0100
SubjectRe: [PATCH v2] memory-hotplug: add automatic onlining policy for the newly added memory
Message-ID<qNej0-4AS-17@gated-at.bofh.it>
In reply to#1300638
David Vrabel <david.vrabel@citrix.com> 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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