From: Boqun Feng <boqun.feng@gmail.com>
To: Benno Lossin <lossin@kernel.org>
Cc: linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org,
lkmm@lists.linux.dev, linux-arch@vger.kernel.org,
"Miguel Ojeda" <ojeda@kernel.org>,
"Alex Gaynor" <alex.gaynor@gmail.com>,
"Gary Guo" <gary@garyguo.net>,
"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
"Andreas Hindborg" <a.hindborg@kernel.org>,
"Alice Ryhl" <aliceryhl@google.com>,
"Trevor Gross" <tmgross@umich.edu>,
"Danilo Krummrich" <dakr@kernel.org>,
"Will Deacon" <will@kernel.org>,
"Peter Zijlstra" <peterz@infradead.org>,
"Mark Rutland" <mark.rutland@arm.com>,
"Wedson Almeida Filho" <wedsonaf@gmail.com>,
"Viresh Kumar" <viresh.kumar@linaro.org>,
"Lyude Paul" <lyude@redhat.com>, "Ingo Molnar" <mingo@kernel.org>,
"Mitchell Levy" <levymitchell0@gmail.com>,
"Paul E. McKenney" <paulmck@kernel.org>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Linus Torvalds" <torvalds@linux-foundation.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Alan Stern" <stern@rowland.harvard.edu>
Subject: Re: [PATCH v6 4/9] rust: sync: atomic: Add generic atomics
Date: Fri, 11 Jul 2025 14:25:20 -0700 [thread overview]
Message-ID: <aHGBQLSzOq6RsqKt@tardis-2.local> (raw)
In-Reply-To: <DB9FX5XAK4JJ.3GTCC6Z5EHARV@kernel.org>
On Fri, Jul 11, 2025 at 08:34:07PM +0200, Benno Lossin wrote:
[...]
> >
> > So all your disagreement is about the "extra safety requirement" part?
> > How about I drop that:
> >
> > /// Returns a pointer to the underlying atomic `T`.
> > pub const fn as_ptr(&self) -> *mut T {
> > self.0.get()
> > }
>
> Yes that's what I had in mind.
>
> > ? I tried to add something additional information:
> >
> > /// Note that non-atomic reads and writes via the returned pointer may
> > /// cause data races if racing with atomic reads and writes per [LKMM].
> >
> > but that seems redundant, because as you said, data races are UB anyway.
>
> Yeah... I don't think the stdlib docs are too useful on this function:
>
> Doing non-atomic reads and writes on the resulting integer can be a data
> race. This method is mostly useful for FFI, where the function signature
> may use *mut i32 instead of &AtomicI32.
>
> Returning an *mut pointer from a shared reference to this atomic is safe
> because the atomic types work with interior mutability. All
> modifications of an atomic change the value through a shared reference,
> and can do so safely as long as they use atomic operations. Any use of
> the returned raw pointer requires an unsafe block and still has to
> uphold the same restriction: operations on it must be atomic.
>
> You can mention the use of this function for FFI. People might then be
> discouraged from using it for other things where it doesn't make sense.
>
I'm going to keep it simple at the beginning (i.e. using the one-line
doc comment above). I added it in an issue so that we can revisit it
later:
https://github.com/Rust-for-Linux/linux/issues/1180
For your other feebacks on patch #4, I think they are reasonable and I'm
going to apply them, except I may need an extra review on the doc
comment of Atomic<T> when I have it. Thanks!
Regards,
Boqun
> ---
> Cheers,
> Benno
next prev parent reply other threads:[~2025-07-11 21:25 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-07-10 6:00 [PATCH v6 0/9] LKMM generic atomics in Rust Boqun Feng
2025-07-10 6:00 ` [PATCH v6 1/9] rust: Introduce atomic API helpers Boqun Feng
2025-07-10 6:00 ` [PATCH v6 2/9] rust: sync: Add basic atomic operation mapping framework Boqun Feng
2025-07-10 11:04 ` Benno Lossin
2025-07-10 15:12 ` Boqun Feng
2025-07-10 15:46 ` Benno Lossin
2025-07-10 16:16 ` Boqun Feng
2025-07-10 19:21 ` Benno Lossin
2025-07-10 20:29 ` Boqun Feng
2025-07-11 8:15 ` Benno Lossin
2025-07-10 6:00 ` [PATCH v6 3/9] rust: sync: atomic: Add ordering annotation types Boqun Feng
2025-07-10 11:08 ` Benno Lossin
2025-07-10 12:00 ` Andreas Hindborg
2025-07-10 14:42 ` Boqun Feng
2025-07-10 15:05 ` Benno Lossin
2025-07-10 15:57 ` Boqun Feng
2025-07-10 19:19 ` Benno Lossin
2025-07-10 18:32 ` Miguel Ojeda
2025-07-10 19:06 ` Miguel Ojeda
2025-07-10 6:00 ` [PATCH v6 4/9] rust: sync: atomic: Add generic atomics Boqun Feng
2025-07-11 8:03 ` Benno Lossin
2025-07-11 13:22 ` Boqun Feng
2025-07-11 13:34 ` Benno Lossin
2025-07-11 13:51 ` Boqun Feng
2025-07-11 18:34 ` Benno Lossin
2025-07-11 21:25 ` Boqun Feng [this message]
2025-07-11 13:58 ` Boqun Feng
2025-07-11 18:35 ` Benno Lossin
2025-07-14 7:08 ` Boqun Feng
2025-07-13 19:51 ` Boqun Feng
2025-07-10 6:00 ` [PATCH v6 5/9] rust: sync: atomic: Add atomic {cmp,}xchg operations Boqun Feng
2025-07-11 8:42 ` Benno Lossin
2025-07-10 6:00 ` [PATCH v6 6/9] rust: sync: atomic: Add the framework of arithmetic operations Boqun Feng
2025-07-11 8:53 ` Benno Lossin
2025-07-11 14:39 ` Boqun Feng
2025-07-11 17:41 ` Boqun Feng
2025-07-11 19:07 ` Benno Lossin
2025-07-11 18:55 ` Benno Lossin
2025-07-11 19:51 ` Boqun Feng
2025-07-11 21:03 ` Benno Lossin
2025-07-11 21:22 ` Boqun Feng
2025-07-14 4:20 ` Boqun Feng
2025-07-10 6:00 ` [PATCH v6 7/9] rust: sync: atomic: Add Atomic<u{32,64}> Boqun Feng
2025-07-11 8:54 ` Benno Lossin
2025-07-10 6:00 ` [PATCH v6 8/9] rust: sync: Add memory barriers Boqun Feng
2025-07-11 8:57 ` Benno Lossin
2025-07-11 13:32 ` Boqun Feng
2025-07-11 18:57 ` Benno Lossin
2025-07-11 19:26 ` Boqun Feng
2025-07-11 21:04 ` Benno Lossin
2025-07-11 21:34 ` Boqun Feng
2025-07-11 18:20 ` Boqun Feng
2025-07-14 15:42 ` Ralf Jung
2025-07-15 15:21 ` Boqun Feng
2025-07-15 15:35 ` Ralf Jung
2025-07-15 15:56 ` Boqun Feng
2025-07-16 19:42 ` Ralf Jung
2025-07-10 6:00 ` [PATCH v6 9/9] rust: sync: atomic: Add Atomic<{usize,isize}> Boqun Feng
2025-07-11 9:00 ` Benno Lossin
2025-07-11 13:45 ` Miguel Ojeda
2025-07-11 14:07 ` Boqun Feng
2025-07-11 14:40 ` Miguel Ojeda
2025-07-11 15:46 ` Boqun Feng
2025-07-11 18:35 ` Miguel Ojeda
2025-07-11 19:05 ` Benno Lossin
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