linux-kernel - Re: [PATCH 2/2] rust: sync: atomic: Add atomic operation helpers over raw pointers

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Message-ID: <aW-HLUWC3C9HZIGX@tardis-2.local>
Date: Tue, 20 Jan 2026 21:46:21 +0800
From: Boqun Feng <boqun.feng@...il.com>
To: Gary Guo <gary@...yguo.net>
Cc: linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, kasan-dev@...glegroups.com,
	Will Deacon <will@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Mark Rutland <mark.rutland@....com>,
	Miguel Ojeda <ojeda@...nel.org>,
	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>,
	Elle Rhumsaa <elle@...thered-steel.dev>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Marco Elver <elver@...gle.com>,
	FUJITA Tomonori <fujita.tomonori@...il.com>
Subject: Re: [PATCH 2/2] rust: sync: atomic: Add atomic operation helpers
 over raw pointers

On Tue, Jan 20, 2026 at 01:25:58PM +0000, Gary Guo wrote:
> On Tue Jan 20, 2026 at 11:52 AM GMT, Boqun Feng wrote:
> > In order to synchronize with C or external, atomic operations over raw
> 
> The sentence feels incomplete. Maybe "external memory"? Also "atomic operations
> over raw pointers" isn't a full setence.
> 

Ah, my bad, should be "atomic operations over raw pointers are needed",

> > pointers, althought previously there is always an `Atomic::from_ptr()`
> 
> You mean "already an"?
> 

To me, it's kinda similar, but let's use "already"

> > to provide a `&Atomic<T>`. However it's more convenient to have helpers
> > that directly perform atomic operations on raw pointers. Hence a few are
> > added, which are basically a `Atomic::from_ptr().op()` wrapper.
> >
> > Note: for naming, since `atomic_xchg()` and `atomic_cmpxchg()` has a
> > conflict naming to 32bit C atomic xchg/cmpxchg, hence they are just
> > named as `xchg()` and `cmpxchg()`. For `atomic_load()` and
> > `atomic_store()`, their 32bit C counterparts are `atomic_read()` and
> > `atomic_set()`, so keep the `atomic_` prefix.
> 
> I still have reservation on if this is actually needed. Directly reading from C
> should be rare enough that `Atomic::from_ptr().op()` isn't a big issue. To me,
> `Atomic::from_ptr` has the meaning of "we know this is a field that needs atomic
> access, but bindgen can't directly generate a `Atomic<T>`", and it will
> encourage one to check if this is actually true, while `atomic_op` doesn't feel
> the same.
> 

These are valid points, but personally I feel it's hard to prevent
people to add these themselves ;)

> That said, if it's decided that this is indeed needed, then
> 
> Reviewed-by: Gary Guo <gary@...yguo.net>
> 

Thank you.

> with the grammar in the commit message fixed.
> 

The new commit log now:

In order to synchronize with C or external memory, atomic operations
over raw pointers are need. Although there is already an
`Atomic::from_ptr()` to provide a `&Atomic<T>`, it's more convenient to
have helpers that directly perform atomic operations on raw pointers.
Hence a few are added, which are basically an `Atomic::from_ptr().op()`
wrapper.

Note: for naming, since `atomic_xchg()` and `atomic_cmpxchg()` have a
conflict naming to 32bit C atomic xchg/cmpxchg, hence the helpers are
just named as `xchg()` and `cmpxchg()`. For `atomic_load()` and
`atomic_store()`, their 32bit C counterparts are `atomic_read()` and
`atomic_set()`, so keep the `atomic_` prefix.


Regards,
Boqun