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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id x24sm977024qkn.48.2020.02.26.03.50.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 26 Feb 2020 03:50:02 -0800 (PST) Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable From: Qian Cai Mime-Version: 1.0 (1.0) Subject: Re: [PATCH v2] mm/vmscan: fix data races at kswapd_classzone_idx Date: Wed, 26 Feb 2020 06:50:01 -0500 Message-Id: <8C6CE0C4-7B15-41D5-A1B2-F48F6241200F@lca.pw> References: <20200226040612.GW24185@bombadil.infradead.org> Cc: akpm@linux-foundation.org, elver@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org In-Reply-To: <20200226040612.GW24185@bombadil.infradead.org> To: Matthew Wilcox X-Mailer: iPhone Mail (17D50) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000047, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > On Feb 25, 2020, at 11:06 PM, Matthew Wilcox wrote: >=20 > I don't understand why the usages of kswapd_classzone_idx in kswapd() and > kswapd_try_to_sleep() don't need changing too? kswapd_classzone_idx() > looks safe to me, but I'm prone to missing stupid things that compilers > are allowed to do. I am not sure. Although it looks possible on paper, I am wondering why KCSAN= did not trigger it yet which seems rather common. I did stress testing thos= e areas with KCSAN for a few months now, but it might just be that I missed t= he report at the first place. I=E2=80=99ll keep running some testing to confirm it, but until that happens= or someone else could confirm it could happen, I=E2=80=99ll leave it out fo= r this version. We can always submit an incremental patch later if necessary= .=