linux-kernel - Re: C aggregate passing (Rust kernel policy)

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Message-ID: <20250226162655.65ba4b51@gandalf.local.home>
Date: Wed, 26 Feb 2025 16:26:55 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Martin Uecker <uecker@...raz.at>, Ralf Jung <post@...fj.de>, "Paul E.
 McKenney" <paulmck@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>, Ventura
 Jack <venturajack85@...il.com>, Kent Overstreet
 <kent.overstreet@...ux.dev>, Gary Guo <gary@...yguo.net>,
 airlied@...il.com, boqun.feng@...il.com, david.laight.linux@...il.com,
 ej@...i.de, gregkh@...uxfoundation.org, hch@...radead.org, hpa@...or.com,
 ksummit@...ts.linux.dev, linux-kernel@...r.kernel.org,
 miguel.ojeda.sandonis@...il.com, rust-for-linux@...r.kernel.org
Subject: Re: C aggregate passing (Rust kernel policy)

On Wed, 26 Feb 2025 13:14:30 -0800
Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> Similarly, if the source code has a single read, the compiler had
> better not turn that into two reads (because of some register pressure
> issue). That would *ALSO* be a bug, because of the whole TOCTOU issue
> (ie the source code may have had one single access, done sanity
> testing on the value before using it, and if the compiler turned it
> all into "read+sanity test" and "read+use", the compiler is
> introducing behavioral differences).

As a bystander here, I just want to ask, do you mean basically to treat all
reads as READ_ONCE() and all writes as WRITE_ONCE()?

-- Steve