lkml.org 
[lkml]   [2020]   [Jan]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH -next v4] mm/hotplug: silence a lockdep splat with printk()
On Fri 17-01-20 10:25:06, David Hildenbrand wrote:
> On 17.01.20 09:59, Michal Hocko wrote:
> > On Fri 17-01-20 09:51:05, David Hildenbrand wrote:
> >> On 17.01.20 03:21, Qian Cai wrote:
> > [...]
> >>> Even though has_unmovable_pages doesn't hold any reference to the
> >>> returned page this should be reasonably safe for the purpose of
> >>> reporting the page (dump_page) because it cannot be hotremoved. The
> >>
> >> This is only true in the context of memory unplug, but not in the
> >> context of is_mem_section_removable()-> is_pageblock_removable_nolock().
> >
> > Well, the above should hold for that path as well AFAICS. If the page is
> > unmovable then a racing hotplug cannot remove it, right? Or do you
> > consider a temporary unmovability to be a problem?
>
> Somebody could test /sys/devices/system/memory/memoryX/removable. While
> returning the unmovable page, it could become movable and
> offlining+removing could succeed.

Doesn't this path use device lock or something? If not than the new code
is not more racy then the existing one. Just look at
is_pageblock_removable_nolock and how it dereferences struct page
(page_zonenum in page_zone.)
--
Michal Hocko
SUSE Labs

\
 
 \ /
  Last update: 2020-01-17 10:40    [W:0.062 / U:0.660 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site