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[209.85.208.175]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-538a0440b8fsm374032e87.248.2024.09.27.10.32.00 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 27 Sep 2024 10:32:00 -0700 (PDT) Received: by mail-lj1-f175.google.com with SMTP id 38308e7fff4ca-2fabb837ddbso13114251fa.1 for ; Fri, 27 Sep 2024 10:32:00 -0700 (PDT) X-Forwarded-Encrypted: i=1; AJvYcCVlRSP6TER+L98GESE/afKQNsbxc3M+Wnk0xy/B/m3qsyVsvidlR855uz5KmcOy5FKVGRn/PU2GNw==@kvack.org X-Received: by 2002:adf:8b1b:0:b0:374:ba2b:4d1c with SMTP id ffacd0b85a97d-37cd5aa684emr3408839f8f.31.1727457821824; Fri, 27 Sep 2024 10:23:41 -0700 (PDT) MIME-Version: 1.0 References: <4167e6f5-4ff9-4aaa-915e-c1e692ac785a@efficios.com> <48992c9f-6c61-4716-977c-66e946adb399@efficios.com> <2b2aea37-06fe-40cb-8458-9408406ebda6@efficios.com> <55633835-242c-4d7f-875b-24b16f17939c@huaweicloud.com> <54487a36-f74c-46c3-aed7-fc86eaaa9ca2@huaweicloud.com> <0b262fe5-2fc5-478d-bf66-f208723238d5@efficios.com> <7e1c8a5e-c110-414c-8fb2-022eacc2bd4a@efficios.com> In-Reply-To: <7e1c8a5e-c110-414c-8fb2-022eacc2bd4a@efficios.com> From: Linus Torvalds Date: Fri, 27 Sep 2024 10:23:24 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [RFC PATCH 1/4] hazptr: Add initial implementation of hazard pointers To: Mathieu Desnoyers Cc: Boqun Feng , Jonas Oberhauser , linux-kernel@vger.kernel.org, rcu@vger.kernel.org, linux-mm@kvack.org, lkmm@lists.linux.dev, "Paul E. McKenney" , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , "Uladzislau Rezki (Sony)" , rostedt , Lai Jiangshan , Zqiang , Peter Zijlstra , Ingo Molnar , Will Deacon , Waiman Long , Mark Rutland , Thomas Gleixner , Kent Overstreet , Vlastimil Babka , maged.michael@gmail.com, Neeraj Upadhyay , Greg Kroah-Hartman Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: CEE691C0017 X-Stat-Signature: indtufw6ythqyqeyk1nia7g98tar7ego X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1727458323-614663 X-HE-Meta: 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 BTjkQQWo 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 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 Fri, 27 Sept 2024 at 10:17, Mathieu Desnoyers wrote: > > The barrier() is ineffective at fixing the issue. > It does not prevent the compiler CSE from losing the > address dependency: Ok. Thanks for actually specifying code. That needs to be (a) in a comment (b) the value barrier needs to be on *both* values so that the order of the equality testing doesn't matter. > I'm preparing a small series that aims to show how a minimal > hazard pointer implementation can help improve common scenarios: I want actual numbers on real loads. Just so you know. Not "this can help". But "this actually really _does_ help". Linus