Received-SPF: pass (google.com: domain of linux-kernel+bounces-215037-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.48.161 as permitted sender) client-ip=147.75.48.161;
Feedback-ID: iad51458e:Fastmail
Date: Fri, 14 Jun 2024 07:33:41 -0700
From: Boqun Feng <boqun.feng@gmail.com>
To: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Cc: Gary Guo <gary@garyguo.net>, rust-for-linux@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
	llvm@lists.linux.dev, Miguel Ojeda <ojeda@kernel.org>,
	Alex Gaynor <alex.gaynor@gmail.com>,
	Wedson Almeida Filho <wedsonaf@gmail.com>,
	=?iso-8859-1?Q?Bj=F6rn?= Roy Baron <bjorn3_gh@protonmail.com>,
	Benno Lossin <benno.lossin@proton.me>,
	Andreas Hindborg <a.hindborg@samsung.com>,
	Alice Ryhl <aliceryhl@google.com>,
	Alan Stern <stern@rowland.harvard.edu>,
	Andrea Parri <parri.andrea@gmail.com>,	Will Deacon <will@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Nicholas Piggin <npiggin@gmail.com>,	David Howells <dhowells@redhat.com>,
	Jade Alglave <j.alglave@ucl.ac.uk>,	Luc Maranget <luc.maranget@inria.fr>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Akira Yokosawa <akiyks@gmail.com>,	Daniel Lustig <dlustig@nvidia.com>,
	Joel Fernandes <joel@joelfernandes.org>,
	Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,	kent.overstreet@gmail.com,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>, elver@google.com,
	Mark Rutland <mark.rutland@arm.com>,
	Thomas Gleixner <tglx@linutronix.de>,	Ingo Molnar <mingo@redhat.com>,
 Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
	"H. Peter Anvin" <hpa@zytor.com>,
	Catalin Marinas <catalin.marinas@arm.com>,	torvalds@linux-foundation.org,
 linux-arm-kernel@lists.infradead.org,	linux-fsdevel@vger.kernel.org,
 Trevor Gross <tmgross@umich.edu>,	dakr@redhat.com
Subject: Re: [RFC 2/2] rust: sync: Add atomic support
Message-ID: <ZmxUxaIwHWnB42h-@Boquns-Mac-mini.home>
References: <20240612223025.1158537-1-boqun.feng@gmail.com>
 <20240612223025.1158537-3-boqun.feng@gmail.com>
 <20240613144432.77711a3a@eugeo>
 <ZmseosxVQXdsQjNB@boqun-archlinux>
 <CANiq72myhoCCWs7j0eZuxfoYMbTez7cPa795T57+gz2Dpd+xAw@mail.gmail.com>
 <ZmtC7h7v1t6XJ6EI@boqun-archlinux>
 <CANiq72=JdqTRPiUfT=-YMTTN+bHeAe2Pba8nERxU3cN8Q-BEOw@mail.gmail.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <CANiq72=JdqTRPiUfT=-YMTTN+bHeAe2Pba8nERxU3cN8Q-BEOw@mail.gmail.com>

On Fri, Jun 14, 2024 at 11:59:58AM +0200, Miguel Ojeda wrote:
> On Thu, Jun 13, 2024 at 9:05 PM Boqun Feng <boqun.feng@gmail.com> wrote:
> >
> > Does this make sense?
> 
> Implementation-wise, if you think it is simpler or more clear/elegant
> to have the extra lower level layer, then that sounds fine.
> 
> However, I was mainly talking about what we would eventually expose to
> users, i.e. do we want to provide `Atomic<T>` to begin with? If yes,

The truth is I don't know ;-) I don't have much data on which one is
better. Personally, I think AtomicI32 and AtomicI64 make the users have
to think about size, alignment, etc, and I think that's important for
atomic users and people who review their code, because before one uses
atomics, one should ask themselves: why don't I use a lock? Atomics
provide the ablities to do low level stuffs and when doing low level
stuffs, you want to be more explicit than ergonomic.

That said, I keep an open mind on `Atomic<T>`, maybe it will show its
value at last. But right now, I'm not convinced personally.

> then we could make the lower layer private already.
> 
> We can defer that extra layer/work if needed even if we go for
> `Atomic<T>`, but it would be nice to understand if we have consensus
> for an eventual user-facing API, or if someone has any other opinion
> or concerns on one vs. the other.
> 

Yes, that'll be great. I'd love to see others' inputs!

Regards,
Boqun

> Cheers,
> Miguel