Re: [PATCH] mm: convert totalram_pages, totalhigh_pages and managed_pages to atomic.

[Kees Cook]

On Mon, Oct 22, 2018 at 10:11 PM, Konstantin Khlebnikov
<khlebnikov@xxxxxxxxxxxxxx> wrote:
> On 23.10.2018 7:15, Joe Perches wrote:> On Mon, 2018-10-22 at 22:53 +0530,
> Arun KS wrote:
>>> Remove managed_page_count_lock spinlock and instead use atomic
>>> variables.
>>
>> Perhaps better to define and use macros for the accesses
>> instead of specific uses of atomic_long_<inc/dec/read>
>>
>> Something like:
>>
>> #define totalram_pages()      (unsigned
>> long)atomic_long_read(&_totalram_pages)
>
> or proper static inline
> this code isn't so low level for breaking include dependencies with macro

BTW, I noticed a few places in the patch that did multiple evaluations
of totalram_pages. It might be worth fixing those prior to doing the
conversion, too. e.g.:

if (totalram_pages > something)
   foobar(totalram_pages); <- value may have changed here

should, instead, be:

var = totalram_pages; <- get stable view of the value
if (var > something)
    foobar(var);

-Kees

> [dropped bloated cc - my server rejects this mess]

Thank you -- I was struggling to figure out the best way to reply to this. :)

-Kees

-- 
Kees Cook