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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id m16sm700391qka.8.2020.01.29.01.51.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 29 Jan 2020 01:51:59 -0800 (PST) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable From: Qian Cai Mime-Version: 1.0 (1.0) Subject: Re: [PATCH -next] mm/page_counter: mark intentional data races Date: Wed, 29 Jan 2020 04:51:58 -0500 Message-Id: <9507ADF5-1040-495E-9A39-C0C23412AD64@lca.pw> References: Cc: Michal Hocko , Andrew Morton , Johannes Weiner , Linux Memory Management List , LKML In-Reply-To: To: Marco Elver X-Mailer: iPhone Mail (17C54) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > On Jan 29, 2020, at 4:06 AM, Marco Elver wrote: >=20 > These should be using 'READ_ONCE' and 'WRITE_ONCE' for c->watermark. > Store or load tearing would change the logic here, since the > comparison might see garbage. I originally thought that it probably does not matter because it is racy the= re by doing lockless access anyway. Another thread could change the value at= anytime. Now, I agree set it to a garbage due to a data race could be quite unpleasan= t there.=