linux-kernel - Re: [PATCH 4/5] rust: sync: atomic: Add Atomic<*mut T> support

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Message-ID: <aWz04Tb7SSDQls8T@tardis-2.local>
Date: Sun, 18 Jan 2026 22:57:37 +0800
From: Boqun Feng <boqun.feng@...il.com>
To: Dirk Behme <dirk.behme@...il.com>
Cc: rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
	rcu@...r.kernel.org, Miguel Ojeda <ojeda@...nel.org>,
	Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <lossin@...nel.org>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
	Danilo Krummrich <dakr@...nel.org>, Will Deacon <will@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Mark Rutland <mark.rutland@....com>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Frederic Weisbecker <frederic@...nel.org>,
	Neeraj Upadhyay <neeraj.upadhyay@...nel.org>,
	Joel Fernandes <joelagnelf@...dia.com>,
	Josh Triplett <josh@...htriplett.org>,
	Uladzislau Rezki <urezki@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Zqiang <qiang.zhang@...ux.dev>,
	FUJITA Tomonori <fujita.tomonori@...il.com>
Subject: Re: [PATCH 4/5] rust: sync: atomic: Add Atomic<*mut T> support

On Sun, Jan 18, 2026 at 09:38:36AM +0100, Dirk Behme wrote:
[...]
> >  
> > +// The current helpers of load/store uses `{WRITE,READ}_ONCE()` hence the atomicity is only
> 
> uses -> use ?
> 

Will fix, thank you!

> > +// guaranteed against read-modify-write operations if the architecture supports native atomic RmW.
> > +#[cfg(CONFIG_ARCH_SUPPORTS_ATOMIC_RMW)]
> > +impl AtomicImpl for *const c_void {
> > +    type Delta = isize;
> > +}
> 
> Are all users of this guarded with CONFIG_ARCH_SUPPORTS_ATOMIC_RMW as
> well? Or do we want (need?) to cover the

No, the users don't need to guard with CONFIG_ARCH_SUPPORTS_ATOMIC_RMW,
the purpose of this #[cfg] is to avoid surprise that when
CONFIG_ARCH_SUPPORTS_ATOMIC_RMW=n arch supports Rust, when that happens,
we need to add the support to the helpers of i8/i16/ptr.

> non-CONFIG_ARCH_SUPPORTS_ATOMIC_RMW cases where someone tries to use

Note that these arches are very rare, so we might not have any problem
for a while.

Regards,
Boqun

> this as well?
> 
> Best regards
> 
> Dirk
> 
> 
>