Re: [PATCH 2/2] core-api/memory-hotplug.rst: divide Locking Internal section by different locks

[Wei Yang <richard.weiyang@gmail.com>]

On Wed, Dec 05, 2018 at 09:08:47AM +0100, David Hildenbrand wrote:
>On 05.12.18 03:34, Wei Yang wrote:
>> Currently locking for memory hotplug is a little complicated.
>> 
>> Generally speaking, we leverage the two global lock:
>> 
>>   * device_hotplug_lock
>>   * mem_hotplug_lock
>> 
>> to serialise the process.
>> 
>> While for the long term, we are willing to have more fine-grained lock
>> to provide higher scalability.
>> 
>> This patch divides Locking Internal section based on these two global
>> locks to help readers to understand it. Also it adds some new finding to
>> enrich it.
>> 
>> [David: words arrangement]
>> 
>> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
>> ---
>>  Documentation/core-api/memory-hotplug.rst | 27 ++++++++++++++++++++++++---
>>  1 file changed, 24 insertions(+), 3 deletions(-)
>> 
>> diff --git a/Documentation/core-api/memory-hotplug.rst b/Documentation/core-api/memory-hotplug.rst
>> index de7467e48067..95662b283328 100644
>> --- a/Documentation/core-api/memory-hotplug.rst
>> +++ b/Documentation/core-api/memory-hotplug.rst
>> @@ -89,6 +89,20 @@ NOTIFY_STOP stops further processing of the notification queue.
>>  Locking Internals
>>  =================
>>  
>> +There are three locks involved in memory-hotplug, two global lock and one local
>> +lock:
>> +
>> +- device_hotplug_lock
>> +- mem_hotplug_lock
>> +- device_lock
>> +
>
>Do we really only ever use these three and not anything else when
>adding/removing/onlining/offlining memory?
>
>(I am thinking e.g. about pgdat_resize_lock)

Yes there are more than those three, pgdat_resize_lock is one of them.

>
>If so, you should phrase that maybe more generally Or add more details :)

Yep, while I don't get a whole picture about the pgdat_resize_lock. The
usage of this lock scatter in many places.

>
>"In addition to fine grained locks like pgdat_resize_lock, there are
>three locks involved ..."
>

Sounds better :-)

-- 
Wei Yang
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