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[209.85.208.52]) by smtp.gmail.com with ESMTPSA id ce21-20020a170906b25500b009920e9a3a73sm1882619ejb.115.2023.08.04.15.49.57 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 04 Aug 2023 15:49:57 -0700 (PDT) Received: by mail-ed1-f52.google.com with SMTP id 4fb4d7f45d1cf-52307552b03so3365821a12.0 for ; Fri, 04 Aug 2023 15:49:57 -0700 (PDT) X-Received: by 2002:a05:6402:514:b0:521:d75d:ef69 with SMTP id m20-20020a056402051400b00521d75def69mr2790287edv.31.1691189397521; Fri, 04 Aug 2023 15:49:57 -0700 (PDT) MIME-Version: 1.0 References: <20230708191212.4147700-1-surenb@google.com> <20230708191212.4147700-3-surenb@google.com> <20230804214620.btgwhsszsd7rh6nf@f> In-Reply-To: <20230804214620.btgwhsszsd7rh6nf@f> From: Linus Torvalds Date: Fri, 4 Aug 2023 15:49:40 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v2 3/3] fork: lock VMAs of the parent process when forking To: Mateusz Guzik Cc: Suren Baghdasaryan , akpm@linux-foundation.org, regressions@leemhuis.info, bagasdotme@gmail.com, jacobly.alt@gmail.com, willy@infradead.org, liam.howlett@oracle.com, david@redhat.com, peterx@redhat.com, ldufour@linux.ibm.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org, gregkh@linuxfoundation.org, regressions@lists.linux.dev, Jiri Slaby , =?UTF-8?Q?Holger_Hoffst=C3=A4tte?= , stable@vger.kernel.org Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 99ADDA000D X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: q81w33fzkd7mnzgu6dqxnej3ifdrefb9 X-HE-Tag: 1691189401-599774 X-HE-Meta: U2FsdGVkX19su6YJtYGoV2buLEK6UsemssmGnaSOxGI7L5jzAcJIy7W9uo3D6y18VxsT+RuaMQ4LZaDgNBAJ4p+P4/oGmzFiZvZi98UthrSyuAg3EX/LDzIqW/n1ZTHF9QbwiL6yARuyjWj8ldVOwhl2GPcWO5LhqI0rb55Y++5BOtC9bA9abW0sQW7Qd7WhCeZ1/5YYItn3dmxdQPOPqo6xQkZcr3KxqTMsJeiCNx4D6AfXyzAzLApVnOU1XPe/l845EpMOJw4DyvZOOTbkNkEdkU5Yyh2f4FKw03jK2HcolmtWWPWSoLM43hW+HXH06ZkY4RtGtaQRFC9Pqqeom6g0uM2l/cpZ7tKksPGVU+XKLvqGWURuANpRovxmonuWWJgrYkl0tPeG2I/f6hZMef/mh3fg6B13CBL3CD0qUUoI5iEmfQeGxZBFDWeYmvsv+QcchIwX7xHatusKikcdNDdIzpajYBnXYQFYSIQU8RMvJSwD1C/6JvZ+Pa8ePEBt5z9R2Mvd9KLstsvqGTRdeORvgU1X5xMfnxpP12r1wGJqsv2E2ED8ZnFGTasHGc5GYYIt1DI1vA8H28VJOZ/faFIpewXIbxf5hlWKf8uN2tyH8tiVVaW0YVLKM8Po6zHoz7vBtWj1zximH4e14R1M111eH5PWRTPe1+mq8X+Wa/qMzQ/eCuRAX9UwMft1vQO24YF808jhv0i+gP2/RFlsl/FeQtw5kmMqO8MFMVxIldZN21DCqAnEORQuxTR2if85QMJeIr8zep/UN1iU9Gy9ZdAlePObsiVsKtTE6nyFP/fy4HqMOcuT1toJ0nngnXnDZAJ6FxxRyQem7cKL9W3h52dwUalPQktYjabuFsWFw7GawLQ2IxlaE7fi2OPb70XdQI2tpRe8VNM5qzWZSRIosGB+hn/woKPnegUn2OO5xR7iAJOFxp1exA7pHeIcbD/RHzrfybq7DvWURVYqv6h GBH2HKTG 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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 Fri, 4 Aug 2023 at 14:46, Mateusz Guzik wrote: > > I don't see it mentioned in the discussion, so at a risk of ruffling > feathers or looking really bad I'm going to ask: is the locking of any > use if the forking process is single-threaded? T Sadly, we've always been able to access the mm from other processes, so the locking is - I think - unavoidable. And some of those "access from other processes" aren't even uncommon or special. It's things like "ps" etc, that do it just to see the process name and arguments. Linus