On Mon, Nov 26, 2018 at 09:16:08AM +0100, Michal Hocko wrote:
>On Mon 26-11-18 10:28:40, Wei Yang wrote:
>[...]
>> But I get some difficulty to understand this TODO. You want to get rid of
>> these lock? While these locks seem necessary to protect those data of
>> pgdat/zone. Would you mind sharing more on this statement?
>
>Why do we need this lock to be irqsave? Is there any caller that uses
>the lock from the IRQ context?
Went through the code, we have totally 9 place acquire
pgdat_resize_lock:
lib/show_mem.c: 1 show_mem()
mm/memory_hotplug.c: 4 online/offline_pages/__remove_zone()
mm/page_alloc.c: 2 defer_init
mm/sparse.c: 2 not necessary
Two places I am not sure:
* show_mem() would be called from __alloc_pages_slowpath()
* __remove_zone() is related to acpi_scan() on x86, may related to
other method on different arch
I am not 100% for sure, while they looks like to be called in IRQ
context.
My ugly idea is:
* drop pgdat_resize_lock in show_mem(), we don't change the value
here. or replace this with a read/write lock?
* can we adjust pgdat's range in offline_pages()? This would be
consistent since we adjust them in online_pages().
>--
>Michal Hocko
>SUSE Labs
--
Wei Yang
Help you, Help me
