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Thu, 27 Jul 2023 13:11:59 -0700 (PDT) Received: from smtpclient.apple ([66.170.99.1]) by smtp.gmail.com with ESMTPSA id v5-20020a170902b7c500b001b891259eddsm2015611plz.197.2023.07.27.13.11.58 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Thu, 27 Jul 2023 13:11:59 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3731.700.6\)) Subject: Re: [PATCH 0/2] fix vma->anon_vma check for per-VMA locking; fix anon_vma memory ordering From: Nadav Amit In-Reply-To: Date: Thu, 27 Jul 2023 13:11:43 -0700 Cc: Will Deacon , Jann Horn , "Paul E. McKenney" , Andrew Morton , Peter Zijlstra , Suren Baghdasaryan , Matthew Wilcox , Linux Kernel Mailing List , linux-mm , Alan Stern , Andrea Parri , Boqun Feng , Nicholas Piggin , David Howells , Jade Alglave , Luc Maranget , Akira Yokosawa , Daniel Lustig , Joel Fernandes Content-Transfer-Encoding: quoted-printable Message-Id: <2229115A-23F2-4B6B-800C-7182199DF79D@gmail.com> References: <20230726214103.3261108-1-jannh@google.com> <31df93bd-4862-432c-8135-5595ffd2bd43@paulmck-laptop> <20230727145747.GB19940@willie-the-truck> <8EA729DD-F1CE-4C6F-A074-147A6A1BBCE0@gmail.com> To: Linus Torvalds X-Mailer: Apple Mail (2.3731.700.6) X-Stat-Signature: frxbq8ad6ryjd8o4gy5m84ci13iu9w86 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 4B52B120028 X-Rspam-User: X-HE-Tag: 1690488721-851888 X-HE-Meta: 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 7EVfHGfF 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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: > On Jul 27, 2023, at 12:39 PM, Linus Torvalds = wrote: >=20 > On Thu, 27 Jul 2023 at 12:10, Nadav Amit wrote: >>=20 >> Interesting. I wonder if you considered adding to READ_ONCE() = something >> like: >>=20 >> asm volatile("" : "+g" (x) ); >>=20 >> So later loads (such as baz =3D *ptr) would reload the updated value. >=20 > Not necessarily a bad idea. Although I suspect you'd want to add > *two* of them - on either side - to make sure any previous loads > wouldn't be moved around it either. You are right, two are needed. I=E2=80=99ll give it a shot and see if I see changes to the binary.