From: Peter Zijlstra <peterz@infradead.org>
To: Boqun Feng <boqun.feng@gmail.com>
Cc: "Andreas Hindborg" <a.hindborg@kernel.org>,
"Alice Ryhl" <aliceryhl@google.com>,
"Gary Guo" <gary@garyguo.net>, "Will Deacon" <will@kernel.org>,
"Paul E. McKenney" <paulmck@kernel.org>,
"Richard Henderson" <richard.henderson@linaro.org>,
"Matt Turner" <mattst88@gmail.com>,
"Magnus Lindholm" <linmag7@gmail.com>,
"Catalin Marinas" <catalin.marinas@arm.com>,
"Miguel Ojeda" <ojeda@kernel.org>,
"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
"Benno Lossin" <lossin@kernel.org>,
"Trevor Gross" <tmgross@umich.edu>,
"Danilo Krummrich" <dakr@kernel.org>,
"Mark Rutland" <mark.rutland@arm.com>,
"FUJITA Tomonori" <fujita.tomonori@gmail.com>,
"Frederic Weisbecker" <frederic@kernel.org>,
"Lyude Paul" <lyude@redhat.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Anna-Maria Behnsen" <anna-maria@linutronix.de>,
"John Stultz" <jstultz@google.com>,
"Stephen Boyd" <sboyd@kernel.org>,
"Alexander Viro" <viro@zeniv.linux.org.uk>,
"Christian Brauner" <brauner@kernel.org>,
"Jan Kara" <jack@suse.cz>,
linux-kernel@vger.kernel.org, linux-alpha@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
rust-for-linux@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 0/5] Add READ_ONCE and WRITE_ONCE to Rust
Date: Tue, 6 Jan 2026 15:56:22 +0100 [thread overview]
Message-ID: <20260106145622.GB3707837@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <aV0JkZdrZn97-d7d@tardis-2.local>
On Tue, Jan 06, 2026 at 09:09:37PM +0800, Boqun Feng wrote:
> Some C code believes a plain write to a properly aligned location is
> atomic (see KCSAN_ASSUME_PLAIN_WRITES_ATOMIC, and no, this doesn't mean
> it's recommended to assume such), and I guess that's the case for
> hrtimer, if it's not much a trouble you can replace the plain write with
> WRITE_ONCE() on C side ;-)
GCC used to provide this guarantee, some of the older code was written
on that. GCC no longer provides that guarantee (there are known cases
where it breaks and all that) and newer code should not rely on this.
All such places *SHOULD* be updated to use READ_ONCE/WRITE_ONCE.
next prev parent reply other threads:[~2026-01-06 14:56 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-31 12:22 Alice Ryhl
2025-12-31 12:22 ` [PATCH 1/5] arch: add CONFIG_ARCH_USE_CUSTOM_READ_ONCE for arm64/alpha Alice Ryhl
2025-12-31 12:22 ` [PATCH 2/5] rust: sync: add READ_ONCE and WRITE_ONCE Alice Ryhl
2026-01-06 12:29 ` Andreas Hindborg
2026-01-06 12:53 ` Boqun Feng
2025-12-31 12:22 ` [PATCH 3/5] rust: sync: support using bool with READ_ONCE Alice Ryhl
2025-12-31 15:25 ` Gary Guo
2026-01-06 12:43 ` Peter Zijlstra
2026-01-06 12:51 ` Alice Ryhl
2026-01-06 18:12 ` Gary Guo
2026-01-07 8:33 ` Peter Zijlstra
2026-01-07 18:12 ` Gary Guo
2025-12-31 12:22 ` [PATCH 4/5] rust: hrtimer: use READ_ONCE instead of read_volatile Alice Ryhl
2026-01-01 2:11 ` FUJITA Tomonori
2026-01-01 4:00 ` FUJITA Tomonori
2026-01-06 12:37 ` Andreas Hindborg
2026-01-06 13:28 ` FUJITA Tomonori
2026-01-07 10:11 ` Andreas Hindborg
2026-01-07 11:22 ` FUJITA Tomonori
2026-01-07 18:21 ` Andreas Hindborg
2026-01-09 2:10 ` FUJITA Tomonori
2026-01-09 10:42 ` Andreas Hindborg
2026-01-07 11:51 ` Boqun Feng
2026-01-07 12:48 ` Andreas Hindborg
2026-01-06 15:23 ` Gary Guo
2026-01-06 18:43 ` Alice Ryhl
2026-01-07 0:47 ` John Hubbard
2026-01-07 1:08 ` Boqun Feng
2026-01-07 2:59 ` John Hubbard
2026-01-07 1:18 ` Boqun Feng
2025-12-31 12:22 ` [PATCH 5/5] rust: fs: " Alice Ryhl
2026-01-21 0:47 ` Boqun Feng
2025-12-31 15:12 ` [PATCH 0/5] Add READ_ONCE and WRITE_ONCE to Rust Gary Guo
2026-01-01 0:53 ` Alice Ryhl
2026-01-01 1:13 ` Boqun Feng
2026-01-06 12:41 ` Andreas Hindborg
2026-01-06 13:09 ` Boqun Feng
2026-01-06 14:56 ` Peter Zijlstra [this message]
2026-01-06 18:18 ` Paul E. McKenney
2026-01-06 19:28 ` Marco Elver
2026-01-09 2:09 ` Paul E. McKenney
2026-01-09 12:00 ` Marco Elver
2026-01-07 8:43 ` Peter Zijlstra
2026-01-07 19:17 ` Paul E. McKenney
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