From: Michal Hocko <mhocko@kernel.org>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Baoquan He <bhe@redhat.com>, David Hildenbrand <david@redhat.com>,
linux-mm@kvack.org, pifang@redhat.com,
linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
aarcange@redhat.com, Mel Gorman <mgorman@suse.de>,
Hugh Dickins <hughd@google.com>
Subject: Re: Memory hotplug softlock issue
Date: Mon, 19 Nov 2018 18:01:05 +0100 [thread overview]
Message-ID: <20181119170105.GT22247@dhcp22.suse.cz> (raw)
In-Reply-To: <6017b36f-3e29-c2ad-f2d1-2ebd77bbaef1@suse.cz>
On Mon 19-11-18 17:48:35, Vlastimil Babka wrote:
> On 11/19/18 5:46 PM, Vlastimil Babka wrote:
> > On 11/19/18 5:46 PM, Michal Hocko wrote:
> >> On Mon 19-11-18 17:36:21, Vlastimil Babka wrote:
> >>>
> >>> So what protects us from locking a page whose refcount dropped to zero?
> >>> and is being freed? The checks in freeing path won't be happy about a
> >>> stray lock.
> >>
> >> Nothing really prevents that. But does it matter. The worst that might
> >> happen is that we lock a freed or reused page. Who would complain?
> >
> > free_pages_check() for example
> >
> > PAGE_FLAGS_CHECK_AT_FREE includes PG_locked
Right you are.
> And besides... what about the last page being offlined and then the
> whole struct page's part of vmemmap destroyed as the node goes away?
Yeah, that is quite unlikely though because the there is quite a large
time window between the two events. I am not entirely sure we are safe
right now TBH. Any access to the struct page after the put_page is
unsafe theoretically.
Then we have to come up with something more clever I am afraid.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2018-11-19 17:01 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-14 7:09 Memory hotplug softlock issue Baoquan He
2018-11-14 7:16 ` Baoquan He
2018-11-14 7:16 ` Baoquan He
2018-11-14 8:18 ` David Hildenbrand
2018-11-14 9:00 ` Baoquan He
2018-11-14 9:25 ` David Hildenbrand
2018-11-14 9:41 ` Michal Hocko
2018-11-14 9:48 ` David Hildenbrand
2018-11-14 10:04 ` Michal Hocko
2018-11-14 9:01 ` Michal Hocko
2018-11-14 9:22 ` David Hildenbrand
2018-11-14 9:37 ` Michal Hocko
2018-11-14 9:39 ` David Hildenbrand
2018-11-14 14:52 ` Baoquan He
2018-11-14 15:00 ` Michal Hocko
2018-11-15 5:10 ` Baoquan He
2018-11-15 7:30 ` Michal Hocko
2018-11-15 7:53 ` Baoquan He
2018-11-15 8:30 ` Michal Hocko
2018-11-15 9:42 ` David Hildenbrand
2018-11-15 9:52 ` Baoquan He
2018-11-15 9:53 ` David Hildenbrand
2018-11-15 13:12 ` Baoquan He
2018-11-15 13:19 ` Michal Hocko
2018-11-15 13:23 ` Baoquan He
2018-11-15 14:25 ` Michal Hocko
2018-11-15 13:38 ` Baoquan He
2018-11-15 14:32 ` Michal Hocko
2018-11-15 14:34 ` Baoquan He
2018-11-16 1:24 ` Baoquan He
2018-11-16 9:14 ` Michal Hocko
2018-11-17 4:22 ` Baoquan He
2018-11-19 10:52 ` Baoquan He
2018-11-19 12:40 ` Michal Hocko
2018-11-19 12:51 ` Michal Hocko
2018-11-19 14:10 ` Michal Hocko
2018-11-19 16:36 ` Vlastimil Babka
2018-11-19 16:46 ` Michal Hocko
2018-11-19 16:46 ` Vlastimil Babka
2018-11-19 16:48 ` Vlastimil Babka
2018-11-19 17:01 ` Michal Hocko [this message]
2018-11-19 17:33 ` Michal Hocko
2018-11-19 20:34 ` Hugh Dickins
2018-11-19 20:59 ` Michal Hocko
2018-11-20 1:56 ` Baoquan He
2018-11-20 5:44 ` Hugh Dickins
2018-11-20 13:38 ` Vlastimil Babka
2018-11-20 13:58 ` Baoquan He
2018-11-20 13:58 ` Baoquan He
2018-11-20 14:05 ` Michal Hocko
2018-11-20 14:12 ` Baoquan He
2018-11-21 1:21 ` Hugh Dickins
2018-11-21 1:08 ` Hugh Dickins
2018-11-21 3:20 ` Hugh Dickins
2018-11-21 17:31 ` Michal Hocko
2018-11-22 1:53 ` Hugh Dickins
2018-11-14 10:00 ` Michal Hocko
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