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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id p2sm12282513qkm.65.2020.04.27.19.11.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 27 Apr 2020 19:11:14 -0700 (PDT) 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 4/4] mm/slub: Fix sysfs shrink circular locking dependency Date: Mon, 27 Apr 2020 22:11:13 -0400 Message-Id: <28BB8A1C-CFDF-4F5A-8686-537C3CE04818@lca.pw> References: Cc: Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Johannes Weiner , Michal Hocko , Vladimir Davydov , linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Juri Lelli In-Reply-To: To: Waiman Long X-Mailer: iPhone Mail (17D50) 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 Apr 27, 2020, at 9:39 PM, Waiman Long wrote: >=20 > The sequence that was prevented by this patch is "kn->count --> mem_hotplu= g_lock.rwsem". This sequence isn't directly in the splat. Once this link is b= roken, the 3-lock circular loop cannot be formed. Maybe I should modify the c= ommit log to make this point more clear. I don=E2=80=99t know what you are talking about. Once trylock succeed once, y= ou will have kn->count =E2=80=94> cpu/memory_hotplug_lock.=