From: David Rientjes <rientjes@google.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Michal Hocko <mhocko@kernel.org>,
Wei Yang <richardw.yang@linux.intel.com>,
hannes@cmpxchg.org, vdavydov.dev@gmail.com,
akpm@linux-foundation.org, cgroups@vger.kernel.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
kirill.shutemov@linux.intel.com, yang.shi@linux.alibaba.com,
alexander.duyck@gmail.com
Subject: Re: [Patch v2] mm: thp: grab the lock before manipulation defer list
Date: Tue, 14 Jan 2020 12:57:22 -0800 (PST) [thread overview]
Message-ID: <alpine.DEB.2.21.2001141254460.84781@chino.kir.corp.google.com> (raw)
In-Reply-To: <20200114105921.eo2vdwikrvtt3gkb@box>
On Tue, 14 Jan 2020, Kirill A. Shutemov wrote:
> split_huge_page_to_list() has page lock taken.
>
> free_transhuge_page() is in the free path and doesn't susceptible to the
> race.
>
> deferred_split_scan() is trickier. list_move() should be safe against
> list_empty() as it will not produce false-positive list_empty().
> list_del_init() *should* (correct me if I'm wrong) be safe because the page
> is freeing and memcg will not touch the page anymore.
>
> deferred_split_huge_page() is a problematic one. It called from
> page_remove_rmap() path witch does require page lock. I don't see any
> obvious way to exclude race with mem_cgroup_move_account() here.
> Anybody else?
>
> Wei, could you rewrite the commit message with deferred_split_huge_page()
> as a race source instead of split_huge_page_to_list()?
>
I think describing the race in terms of deferred_split_huge_page() makes
the most sense and I'd prefer a cc to stable for 5.4+. Even getting the
split_queue_len, which is unsigned long, to underflow because of a
list_empty(page_deferred_list()) check that is no longer accurate after
the lock is taken would be a significant issue for shrinkers.
next prev parent reply other threads:[~2020-01-14 20:57 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-09 14:30 Wei Yang
2020-01-09 18:52 ` David Rientjes
2020-01-09 18:58 ` Michal Hocko
2020-01-11 0:03 ` Kirill A. Shutemov
2020-01-12 2:28 ` Wei Yang
2020-01-12 22:57 ` Kirill A. Shutemov
2020-01-13 0:44 ` Wei Yang
2020-01-13 7:36 ` Kirill A. Shutemov
2020-01-13 8:23 ` Wei Yang
2020-01-14 9:31 ` Michal Hocko
2020-01-14 10:31 ` Kirill A. Shutemov
2020-01-14 10:59 ` Kirill A. Shutemov
2020-01-14 20:57 ` David Rientjes [this message]
2020-01-15 1:19 ` Wei Yang
2020-01-15 1:07 ` Wei Yang
2020-01-15 3:26 ` David Rientjes
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