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[209.85.218.48]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5e4c3b4a734sm175885a12.4.2025.02.26.15.19.05 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 26 Feb 2025 15:19:06 -0800 (PST) Received: by mail-ej1-f48.google.com with SMTP id a640c23a62f3a-abb75200275so42832866b.3 for ; Wed, 26 Feb 2025 15:19:05 -0800 (PST) X-Forwarded-Encrypted: i=1; AJvYcCVX81pWqWDXzZSuDtvEAS/rryAxhBoZxIgc68zEDDt2jXjIy9qKhLlqttlP/fPKHmuJY8H8fCq6@lists.linux.dev X-Received: by 2002:a17:907:72d1:b0:abb:e7de:f2a6 with SMTP id a640c23a62f3a-abc09e35401mr2910896766b.53.1740611944724; Wed, 26 Feb 2025 15:19:04 -0800 (PST) Precedence: bulk X-Mailing-List: ksummit@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <6pwjvkejyw2wjxobu6ffeyolkk2fppuuvyrzqpigchqzhclnhm@v5zhfpmirk2c> <5d7363b0-785c-4101-8047-27cb7afb0364@ralfj.de> <20250226162655.65ba4b51@gandalf.local.home> <20250226165619.64998576@gandalf.local.home> <20250226171321.714f3b75@gandalf.local.home> <20250226173534.44b42190@gandalf.local.home> In-Reply-To: <20250226173534.44b42190@gandalf.local.home> From: Linus Torvalds Date: Wed, 26 Feb 2025 15:18:48 -0800 X-Gmail-Original-Message-ID: X-Gm-Features: AQ5f1JoJL1av6p0bHCUuCTiHUulziFdE8-qs-EcbEYZ32grw4GEJZn_MqtGet6I Message-ID: Subject: Re: C aggregate passing (Rust kernel policy) To: Steven Rostedt Cc: Martin Uecker , Ralf Jung , "Paul E. McKenney" , Alice Ryhl , Ventura Jack , Kent Overstreet , Gary Guo , airlied@gmail.com, boqun.feng@gmail.com, david.laight.linux@gmail.com, ej@inai.de, gregkh@linuxfoundation.org, hch@infradead.org, hpa@zytor.com, ksummit@lists.linux.dev, linux-kernel@vger.kernel.org, miguel.ojeda.sandonis@gmail.com, rust-for-linux@vger.kernel.org Content-Type: text/plain; charset="UTF-8" On Wed, 26 Feb 2025 at 14:34, Steven Rostedt wrote: > > Correct, but if the variable had some other protection, like a lock held > when this function was called, it is fine to do and the compiler may > optimize it or not and still have the same result. Sure. But locking isn't always there. And shouldn't always be there. Lots of lockless algorithms exist, and some of them are very simple indeed ("I set a flag, you read a flag, you get one or the other value") Linus