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[209.85.167.48]) by smtp.gmail.com with ESMTPSA id s14-20020a19770e000000b005188ea5d2b5sm4232478lfc.303.2024.04.29.08.38.45 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 29 Apr 2024 08:38:45 -0700 (PDT) Received: by mail-lf1-f48.google.com with SMTP id 2adb3069b0e04-5176f217b7bso7946288e87.0 for ; Mon, 29 Apr 2024 08:38:45 -0700 (PDT) X-Forwarded-Encrypted: i=1; AJvYcCXYVeQuBW+axr4igMRrJgAbqWZi8+Y+s1uNZX/g55pw3Rp4dTp0hDwPKSkRcgpDoxNw9BsVNQg39kkm/pLOdCfBOJjIv/HlpBCO3OXU X-Received: by 2002:a19:5f5d:0:b0:512:e02f:9fa7 with SMTP id a29-20020a195f5d000000b00512e02f9fa7mr8210499lfj.1.1714405125069; Mon, 29 Apr 2024 08:38:45 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20230424004431.GG3390869@ZenIV> <8e21256a-736e-4c2d-1ff4-723775bcac46@I-love.SAKURA.ne.jp> <2fca7932-5030-32c3-dd61-48dd78e58e11@I-love.SAKURA.ne.jp> <20230425160344.GS3390869@ZenIV> <1b405689-ea0a-6696-6709-d372ce72d68c@I-love.SAKURA.ne.jp> <5cebade5-0aa9-506c-c817-7bcf098eba89@I-love.SAKURA.ne.jp> <2023053005-alongside-unvisited-d9af@gregkh> <8edbd558-a05f-c775-4d0c-09367e688682@I-love.SAKURA.ne.jp> <2023053048-saved-undated-9adf@gregkh> <18a58415-4aa9-4cba-97d2-b70384407313@I-love.SAKURA.ne.jp> In-Reply-To: From: Linus Torvalds Date: Mon, 29 Apr 2024 08:38:28 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v3] tty: tty_io: remove hung_up_tty_fops To: Marco Elver Cc: Tetsuo Handa , Greg Kroah-Hartman , Dmitry Vyukov , syzbot , linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, Nathan Chancellor , Arnd Bergmann , Al Viro , Jiri Slaby , "Paul E. McKenney" Content-Type: text/plain; charset="UTF-8" On Mon, 29 Apr 2024 at 06:56, Marco Elver wrote: > > A WRITE_ONCE() / READ_ONCE() pair would do it here. What should we use instead? Why would we annotate a "any other code generation is insane" issues at all? When we do chained pointer loads in file->f_op->op() and we say "I don't care what value I get for the middle one", I don't see the value in annotating that at all. There is no compiler that will sanely and validly do a pointer chain load by *anything* but a load. And it doesn't matter to us if it then spills and reloads, it will *STILL* be a load. We're not talking about "extract different bits in separate operations". We're talking about following one pointer that can point to two separate static values. Reality matters. A *lot* more than some "C standard" that we already have ignored for decades because it's not strong enough. Linus