From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Michal Hocko <mhocko@kernel.org>
Cc: 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, rientjes@google.com
Subject: Re: [Patch v2] mm: thp: grab the lock before manipulation defer list
Date: Tue, 14 Jan 2020 13:31:12 +0300 [thread overview]
Message-ID: <20200114103112.o6ozdbkfnzdsc2ke@box> (raw)
In-Reply-To: <20200114093122.GH19428@dhcp22.suse.cz>
On Tue, Jan 14, 2020 at 10:31:22AM +0100, Michal Hocko wrote:
> On Sat 11-01-20 03:03:52, Kirill A. Shutemov wrote:
> > On Thu, Jan 09, 2020 at 10:30:54PM +0800, Wei Yang wrote:
> > > As all the other places, we grab the lock before manipulate the defer list.
> > > Current implementation may face a race condition.
> > >
> > > For example, the potential race would be:
> > >
> > > CPU1 CPU2
> > > mem_cgroup_move_account split_huge_page_to_list
> > > !list_empty
> > > lock
> > > !list_empty
> > > list_del
> > > unlock
> > > lock
> > > # !list_empty might not hold anymore
> > > list_del_init
> > > unlock
> >
> > I don't think this particular race is possible. Both parties take page
> > lock before messing with deferred queue, but anytway:
> >
> > Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
>
> I am confused, if the above race is not possible then what would be a
> real race? We really do not want to have a patch with a misleading
> changelog, do we?
The alternative is to make sure that all page_deferred_list() called with
page lock taken.
I'll look into it.
--
Kirill A. Shutemov
next prev parent reply other threads:[~2020-01-14 10:31 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 [this message]
2020-01-14 10:59 ` Kirill A. Shutemov
2020-01-14 20:57 ` David Rientjes
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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