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[209.85.167.44]) by smtp.gmail.com with ESMTPSA id p12-20020a2ea40c000000b002b96a3a87d5sm513236ljn.98.2023.07.27.12.40.02 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 27 Jul 2023 12:40:02 -0700 (PDT) Received: by mail-lf1-f44.google.com with SMTP id 2adb3069b0e04-4fe0d5f719dso2319769e87.2 for ; Thu, 27 Jul 2023 12:40:02 -0700 (PDT) X-Received: by 2002:a05:6512:1591:b0:4fe:8c4:44f4 with SMTP id bp17-20020a056512159100b004fe08c444f4mr115829lfb.62.1690486802107; Thu, 27 Jul 2023 12:40:02 -0700 (PDT) MIME-Version: 1.0 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> In-Reply-To: <8EA729DD-F1CE-4C6F-A074-147A6A1BBCE0@gmail.com> From: Linus Torvalds Date: Thu, 27 Jul 2023 12:39:45 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 0/2] fix vma->anon_vma check for per-VMA locking; fix anon_vma memory ordering To: Nadav Amit 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-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 91DF9C0012 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: 48e1qkb671p6fd9r385jqueet5wpk5gs X-HE-Tag: 1690486804-537014 X-HE-Meta: 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 KXgrrh0H UcN9Uq1e0nPSZm8eyLPzCOxxAREOhV2FsVL+ZvE+50QjvRCbC+chSWfvTfQ7ivfs2J7t6xKz9dmZXXlmdXBC9+ZN4wyaRDkZQ9Ky3JfNX2LE2q4YwWH9R79s5t9TiK5QIYSZ6u+3Df59Yi4fhAdkhSdNtReb2p50DTkSVsYsIFe9zVoVMq3xlPMPU1+BF9gjrBYBxKEnkSF/QdYMsr2qhdy0gylizEse8gqHJdYLV9DSUYIMXNAHF4GgiJXLSufa6/3SwXFzNXYNK/hAsQguyj9NEJUkC1h4s+Cm39HV4hiSclV6g3EYmZeTCgfdAsLa1G9v4WXhgubeLvoPSypnr7b9G0/qm0oAetWVjfnMga17T8LRvQ8werbEDTKxOvTouwGwoitL4PU3URTeNBVCwz41ULkmx1RV6HiWZFbAiu1oR36a3xRlrsiHeSDfhQvIBPKUVd8XOlUi0xhKfK8eHx0IBEA== 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 Thu, 27 Jul 2023 at 12:10, Nadav Amit wrote: > > Interesting. I wonder if you considered adding to READ_ONCE() something > like: > > asm volatile("" : "+g" (x) ); > > So later loads (such as baz = *ptr) would reload the updated value. 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. Linus