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Fri, 03 Jan 2020 16:45:00 -0800 (PST) Received: from [2620:15c:17:3:3a5:23a7:5e32:4598] ([2620:15c:17:3:3a5:23a7:5e32:4598]) by smtp.gmail.com with ESMTPSA id a28sm68401959pfh.119.2020.01.03.16.45.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 03 Jan 2020 16:45:00 -0800 (PST) Date: Fri, 3 Jan 2020 16:44:59 -0800 (PST) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Wei Yang cc: hannes@cmpxchg.org, mhocko@kernel.org, vdavydov.dev@gmail.com, akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, yang.shi@linux.alibaba.com Subject: Re: [RFC PATCH] mm: thp: grab the lock before manipulation defer list In-Reply-To: <20200103233925.GA3678@richard> Message-ID: References: <20200103143407.1089-1-richardw.yang@linux.intel.com> <20200103233925.GA3678@richard> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII 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 Sat, 4 Jan 2020, Wei Yang wrote: > On Fri, Jan 03, 2020 at 11:29:06AM -0800, David Rientjes wrote: > >On Fri, 3 Jan 2020, Wei Yang wrote: > > > >> As all the other places, we grab the lock before manipulate the defer list. > >> Current implementation may face a race condition. > >> > >> Fixes: 87eaceb3faa5 ("mm: thp: make deferred split shrinker memcg aware") > >> > >> Signed-off-by: Wei Yang > >> > >> --- > >> I notice the difference during code reading and just confused about the > >> difference. No specific test is done since limited knowledge about cgroup. > >> > >> Maybe I miss something important? > > > >The check for !list_empty(page_deferred_list(page)) must certainly be > >serialized with doing list_del_init(page_deferred_list(page)). > > > > Hi David > > Would you mind giving more information? You mean list_empty and list_del_init > is atomic? > I mean your patch is obviously correct :) It should likely also have a stable@vger.kernel.org # 5.4+ Acked-by: David Rientjes