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From:   Qian Cai <cai@lca.pw>
Mime-Version: 1.0 (1.0)
Subject: Re: [PATCH] mm: fix a data race in put_page()
Date:   Thu, 6 Feb 2020 10:23:31 -0500
Message-Id: <D022CBB0-C8EC-4F5A-A0B0-893AA7A014AA@lca.pw>
References: <20200206145501.GD26114@quack2.suse.cz>
Cc:     David Hildenbrand <david@redhat.com>, akpm@linux-foundation.org,
        jhubbard@nvidia.com, ira.weiny@intel.com, dan.j.williams@intel.com,
        elver@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org
In-Reply-To: <20200206145501.GD26114@quack2.suse.cz>
To:     Jan Kara <jack@suse.cz>
Sender: linux-kernel-owner@vger.kernel.org
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> On Feb 6, 2020, at 9:55 AM, Jan Kara <jack@suse.cz> wrote:
>=20
> I don't think the problem is real. The question is how to make KCSAN happy=

> in a way that doesn't silence other possibly useful things it can find and=

> also which makes it most obvious to the reader what's going on... IMHO
> using READ_ONCE() fulfills these targets nicely - it is free
> performance-wise in this case, it silences the checker without impacting
> other races on page->flags, its kind of obvious we don't want the load tor=
n
> in this case so it makes sense to the reader (although a comment may be
> nice).

Actually, use the data_race() macro there fulfilling the same purpose too, i=
.e, silence the splat here but still keep searching for other races.=