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[103.168.172.200]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-45da74fabffsm26429431cf.28.2024.10.07.06.48.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 07 Oct 2024 06:48:51 -0700 (PDT) Received: from phl-compute-05.internal (phl-compute-05.phl.internal [10.202.2.45]) by mailfauth.phl.internal (Postfix) with ESMTP id 1B80D120006E; Mon, 7 Oct 2024 09:48:50 -0400 (EDT) Received: from phl-mailfrontend-02 ([10.202.2.163]) by phl-compute-05.internal (MEProxy); Mon, 07 Oct 2024 09:48:50 -0400 X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeeftddrvddvledgieelucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdggtfgfnhhsuhgsshgtrhhisggvpdfu rfetoffkrfgpnffqhgenuceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnh htshculddquddttddmnecujfgurhepfffhvfevuffkfhggtggujgesthdtredttddtvden ucfhrhhomhepuehoqhhunhcuhfgvnhhguceosghoqhhunhdrfhgvnhhgsehgmhgrihhlrd gtohhmqeenucggtffrrghtthgvrhhnpeehudfgudffffetuedtvdehueevledvhfelleei vedtgeeuhfegueevieduffeivdenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmh epmhgrihhlfhhrohhmpegsohhquhhnodhmvghsmhhtphgruhhthhhpvghrshhonhgrlhhi thihqdeiledvgeehtdeigedqudejjeekheehhedvqdgsohhquhhnrdhfvghngheppehgmh grihhlrdgtohhmsehfihigmhgvrdhnrghmvgdpnhgspghrtghpthhtohepfeefpdhmohgu vgepshhmthhpohhuthdprhgtphhtthhopehmrghthhhivghurdguvghsnhhohigvrhhsse gvfhhfihgtihhoshdrtghomhdprhgtphhtthhopehtohhrvhgrlhgusheslhhinhhugidq fhhouhhnuggrthhiohhnrdhorhhgpdhrtghpthhtoheprghkphhmsehlihhnuhigqdhfoh hunhgurghtihhonhdrohhrghdprhgtphhtthhopehpvghtvghriiesihhnfhhrrgguvggr ugdrohhrghdprhgtphhtthhopehlihhnuhigqdhkvghrnhgvlhesvhhgvghrrdhkvghrnh gvlhdrohhrghdprhgtphhtthhopehnphhighhgihhnsehgmhgrihhlrdgtohhmpdhrtghp thhtohepmhhpvgesvghllhgvrhhmrghnrdhiugdrrghupdhrtghpthhtohepghhrvghgkh hhsehlihhnuhigfhhouhhnuggrthhiohhnrdhorhhgpdhrtghpthhtohepsghighgvrghs hieslhhinhhuthhrohhnihigrdguvg X-ME-Proxy: Feedback-ID: iad51458e:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Mon, 7 Oct 2024 09:48:49 -0400 (EDT) Date: Mon, 7 Oct 2024 06:47:31 -0700 From: Boqun Feng To: Mathieu Desnoyers Cc: Linus Torvalds , Andrew Morton , Peter Zijlstra , linux-kernel@vger.kernel.org, Nicholas Piggin , Michael Ellerman , Greg Kroah-Hartman , Sebastian Andrzej Siewior , "Paul E. McKenney" , Will Deacon , Alan Stern , John Stultz , Neeraj Upadhyay , Frederic Weisbecker , Joel Fernandes , Josh Triplett , Uladzislau Rezki , Steven Rostedt , Lai Jiangshan , Zqiang , Ingo Molnar , Waiman Long , Mark Rutland , Thomas Gleixner , Vlastimil Babka , maged.michael@gmail.com, Mateusz Guzik , Jonas Oberhauser , rcu@vger.kernel.org, linux-mm@kvack.org, lkmm@lists.linux.dev Subject: Re: [RFC PATCH 3/4] hp: Implement Hazard Pointers Message-ID: References: <20241002010205.1341915-1-mathieu.desnoyers@efficios.com> <20241002010205.1341915-4-mathieu.desnoyers@efficios.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 6797D180004 X-Stat-Signature: q5qs8b47qrf1s9mekajfq6p55onsmo8u X-Rspam-User: X-HE-Tag: 1728308932-206871 X-HE-Meta: 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 bzsZLb6g Ajj7NhGKa3BZSSYA1wZIN6B1wzM+z0cnt4uiKUbtUOpb6FxIHAy3hE09+jKvklUL1GZNw1Id2I18ZdWhkqG6X/U4047uzcnSEfBGOnu7Y1yYAP72Ns5tG0Db9WqJVkBHf+Q5JIZ0H3G2S2RMTEKMv2PF/9GgJq49okJLgjWF5Wg/kribu69Lxil2174w0BaIDVi/9ju9wstk1AL6UB6gHjH7tsLzvCADGOk9A2jevO644qHEIDIu+ETk3fdCQx7PHqjX8e9gGqGW4l3EBPd2jMU/14JQ5wN2YhGhAe/DtOnAGZGlPwfuoQpjsgaIXzsJ/2Y/xcqa1uW4nxTO3jCTTcmitD6azKBYlTV/x1oBkgH80Dl1zWc2OPU/KYhr1gv5x1Rvw51e8H75Ep1l466Qmy/mr11CCTn7D6dNdPbehqP4MTixdsZ5XAfOtGNpCQRH+BvTVSTf8txCTCxEHMwK7A2mhBXZGcS8CYRZ+ 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: List-Subscribe: List-Unsubscribe: On Thu, Oct 03, 2024 at 09:30:53AM -0400, Mathieu Desnoyers wrote: [...] > > > + /* > > > + * Use RCU dereference without lockdep checks, because > > > + * lockdep is not aware of HP guarantees. > > > + */ > > > + addr2 = rcu_access_pointer(*addr_p); /* Load A */ > > > > Why rcu_access_pointer() instead of READ_ONCE()? Because you want to > > mark the head of address dependency? > > Yes, the intent here is to mark the address dependency and provide > a publication guarantee similar to RCU pairing rcu_assign_pointer > and rcu_dereference. Do you see any reason why READ_ONCE() would > suffice here ? READ_ONCE() also provides address dependencies. See the "DEPENDENCY RELATIONS: data, addr, and ctrl" section in tools/memory-model/Documentation/explanantion.txt. Regards, Boqun > > Thanks, > > Mathieu >