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

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Message-ID: <aWz2oZqMaQHQWe-e@tardis-2.local>
Date: Sun, 18 Jan 2026 23:05:05 +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 10:57:37PM +0800, Boqun Feng wrote:
> 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.
> 

Hmm... I guess at this moment, I probably should do

#[cfg(not(CONFIG_ARCH_SUPPORTS_ATOMIC_RMW))]
static_assert!(false,
               "Support of architectures that don't have native atomic needs to implement helpers in atomic_ext.c");

I can add a patch in the next version if it looks good to everyone.

Regards,
Boqun

> > 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
> > 
> > 
> >