From: Boqun Feng <boqun@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Greg KH" <gregkh@linuxfoundation.org>,
"Andreas Hindborg" <a.hindborg@kernel.org>,
"Alice Ryhl" <aliceryhl@google.com>,
"Lorenzo Stoakes" <lorenzo.stoakes@oracle.com>,
"Liam R. Howlett" <Liam.Howlett@oracle.com>,
"Miguel Ojeda" <ojeda@kernel.org>,
"Boqun Feng" <boqun.feng@gmail.com>,
"Gary Guo" <gary@garyguo.net>,
"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
"Benno Lossin" <lossin@kernel.org>,
"Trevor Gross" <tmgross@umich.edu>,
"Danilo Krummrich" <dakr@kernel.org>,
"Will Deacon" <will@kernel.org>,
"Mark Rutland" <mark.rutland@arm.com>,
linux-mm@kvack.org, rust-for-linux@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] rust: page: add byte-wise atomic memory copy methods
Date: Tue, 17 Feb 2026 07:52:46 -0800 [thread overview]
Message-ID: <aZSOzjdntYOB-DxZ@tardis.local> (raw)
In-Reply-To: <20260217091348.GT1395266@noisy.programming.kicks-ass.net>
On Tue, Feb 17, 2026 at 10:13:48AM +0100, Peter Zijlstra wrote:
> On Fri, Feb 13, 2026 at 08:19:17AM -0800, Boqun Feng wrote:
> > Well, in standard C, technically memcpy() has the same problem as Rust's
> > `core::ptr::copy()` and `core::ptr::copy_nonoverlapping()`, i.e. they
> > are vulnerable to data races. Our in-kernel memcpy() on the other hand
> > doesn't have this problem. Why? Because it's volatile byte-wise atomic
> > per the implementation.
>
> Look at arch/x86/lib/memcpy_64.S, plenty of movq variants there. Not
> byte-wise. Also, not a single atomic operation in sight.
>
Sigh, byte-wise means you at least need to byte-wise atomic, if movq is
atomic at 32bit or 64 bit level in x86, then it's fine implementation
for byte wise. Or you are saying on x86 it can tear at byte level?
Regards,
Boqun
next prev parent reply other threads:[~2026-02-17 15:52 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-12 14:51 Andreas Hindborg
2026-02-12 16:41 ` Boqun Feng
2026-02-12 17:10 ` Andreas Hindborg
2026-02-12 17:23 ` Andreas Hindborg
2026-02-13 9:55 ` Peter Zijlstra
2026-02-13 12:18 ` Greg KH
2026-02-13 12:58 ` Andreas Hindborg
2026-02-13 13:20 ` Greg KH
2026-02-13 14:13 ` Andreas Hindborg
2026-02-13 14:26 ` Peter Zijlstra
2026-02-13 15:34 ` Greg KH
2026-02-13 15:45 ` Boqun Feng
2026-02-13 15:58 ` Greg KH
2026-02-13 16:19 ` Boqun Feng
2026-02-17 9:13 ` Peter Zijlstra
2026-02-17 9:33 ` Alice Ryhl
2026-02-17 9:45 ` Peter Zijlstra
2026-02-17 10:01 ` Alice Ryhl
2026-02-17 10:25 ` Peter Zijlstra
2026-02-17 10:47 ` Alice Ryhl
2026-02-17 11:09 ` Peter Zijlstra
2026-02-17 11:51 ` Alice Ryhl
2026-02-17 12:09 ` Peter Zijlstra
2026-02-17 13:00 ` Peter Zijlstra
2026-02-17 13:54 ` Danilo Krummrich
2026-02-17 15:50 ` Peter Zijlstra
2026-02-17 16:10 ` Danilo Krummrich
2026-02-17 13:09 ` Alice Ryhl
2026-02-17 15:48 ` Peter Zijlstra
2026-02-17 23:39 ` Gary Guo
2026-02-18 8:37 ` Peter Zijlstra
2026-02-18 9:31 ` Alice Ryhl
2026-02-18 10:09 ` Peter Zijlstra
2026-02-17 13:56 ` Andreas Hindborg
2026-02-17 16:04 ` Peter Zijlstra
2026-02-17 18:43 ` Andreas Hindborg
2026-02-17 20:32 ` Jens Axboe
2026-02-17 15:52 ` Boqun Feng [this message]
2026-02-17 9:17 ` Peter Zijlstra
2026-02-17 9:23 ` Peter Zijlstra
2026-02-17 9:37 ` Alice Ryhl
2026-02-17 10:01 ` Peter Zijlstra
2026-02-17 9:33 ` Peter Zijlstra
2026-02-14 0:07 ` Gary Guo
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