what protects page lru list?

what protects page lru list?

[Rajesh Ghanekar]

Hi,
   I am confused with what protects page->lru? Is it both zone->lru_lock or
zone->lock? I can see it being protected either by lru_lock or lock.
Are their any
rules where to use lru_lock and where to use lock?

   I did google but couldn't find anything. Sorry if its already discusses
elsewhere, but I couldn't locate any.

- Rajesh

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Re: what protects page lru list?

[Johannes Weiner]

On Sat, Aug 20, 2011 at 02:11:53AM +0530, Rajesh Ghanekar wrote:
> Hi,
>    I am confused with what protects page->lru? Is it both zone->lru_lock or
> zone->lock? I can see it being protected either by lru_lock or lock.

It's not so much about page->lru but the actual list the page is
linked to.

The zone's lists of unallocated pages are protected by zone->lock,
while the LRU lists with the pages for userspace are protected by
zone->lru_lock.

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Re: what protects page lru list?

[Rajesh Ghanekar]

Thanks Johannes. It makes sense. I was searching for any code in
which pages is on free list and being operated with lru_lock. But as
you said only pages on LRU lists are operated by lru_lock.

I am facing a panic in __rmqueue at list_del where the struct page
is corrupted or probably the free_list is corrupted. The kernel is
2.6.32.43.xxx from SLES11SP1. I will first see if any of the other code
(proprietary) running is not broken.

- Rajesh

On Sat, Aug 20, 2011 at 6:57 PM, Johannes Weiner <jweiner@redhat.com> wrote:
> On Sat, Aug 20, 2011 at 02:11:53AM +0530, Rajesh Ghanekar wrote:
>> Hi,
>>    I am confused with what protects page->lru? Is it both zone->lru_lock or
>> zone->lock? I can see it being protected either by lru_lock or lock.
>
> It's not so much about page->lru but the actual list the page is
> linked to.
>
> The zone's lists of unallocated pages are protected by zone->lock,
> while the LRU lists with the pages for userspace are protected by
> zone->lru_lock.
>

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