From: "D. Jeff Dionne" <djeffdionne@gmail.com>
To: paulmck@kernel.org
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
elver@google.com, akpm@linux-foundation.org, tglx@linutronix.de,
peterz@infradead.org, dianders@chromium.org, pmladek@suse.com,
arnd@arndb.de, torvalds@linux-foundation.org,
kernel-team@meta.com, Andi Shyti <andi.shyti@linux.intel.com>,
Palmer Dabbelt <palmer@rivosinc.com>,
Masami Hiramatsu <mhiramat@kernel.org>,
linux-sh@vger.kernel.org
Subject: Re: [PATCH v2 cmpxchg 12/13] sh: Emulate one-byte cmpxchg
Date: Thu, 2 May 2024 14:42:38 +0900 [thread overview]
Message-ID: <23A87C03-EB55-49A1-BB55-B6136117F0B6@gmail.com> (raw)
In-Reply-To: <b7ae0feb-d401-43ee-8d5f-ce62ca224638@paulmck-laptop>
On May 2, 2024, at 14:07, Paul E. McKenney <paulmck@kernel.org> wrote:
> That would be 8-bit xchg() rather than 8-byte cmpxchg(), correct?
>
> Or am I missing something subtle here that makes sh also support one-byte
> (8-bit) cmpxchg()?
The native SH atomic operation is test and set TAS.B. J2 adds a compare and swap CAS.L instruction, carefully chosen for patent free prior art (s360, IIRC).
The (relatively expensive) encoding space we allocated for CAS.L does not contain size bits.
Not all SH4 patents had expired when J2 was under development, but now have (watch this space). Not sure (me myself) if there are more atomic operations in sh4.
Cheers,
J
>
> Thanx, Paul
next prev parent reply other threads:[~2024-05-02 5:42 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <b67e79d4-06cb-4a45-a906-b9e0fbae22c5@paulmck-laptop>
2024-05-01 23:01 ` [PATCH v2 cmpxchg 12/13] sh: Emulate one-byte cmpxchg Paul E. McKenney
2024-05-02 4:52 ` John Paul Adrian Glaubitz
2024-05-02 5:06 ` Paul E. McKenney
2024-05-02 5:11 ` John Paul Adrian Glaubitz
2024-05-02 13:33 ` Paul E. McKenney
2024-05-02 20:53 ` Al Viro
2024-05-02 21:01 ` alpha cmpxchg.h (was Re: [PATCH v2 cmpxchg 12/13] sh: Emulate one-byte cmpxchg) Al Viro
2024-05-02 22:16 ` Linus Torvalds
2024-05-02 21:18 ` [PATCH v2 cmpxchg 12/13] sh: Emulate one-byte cmpxchg Paul E. McKenney
2024-05-02 22:07 ` Al Viro
2024-05-02 23:12 ` Paul E. McKenney
2024-05-02 23:24 ` Al Viro
2024-05-02 23:45 ` Paul E. McKenney
2024-05-02 23:32 ` Linus Torvalds
2024-05-03 0:16 ` Paul E. McKenney
2024-05-02 21:50 ` Arnd Bergmann
2024-05-02 5:42 ` D. Jeff Dionne [this message]
2024-05-02 11:30 ` Arnd Bergmann
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=23A87C03-EB55-49A1-BB55-B6136117F0B6@gmail.com \
--to=djeffdionne@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=andi.shyti@linux.intel.com \
--cc=arnd@arndb.de \
--cc=dianders@chromium.org \
--cc=elver@google.com \
--cc=glaubitz@physik.fu-berlin.de \
--cc=kernel-team@meta.com \
--cc=linux-arch@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-sh@vger.kernel.org \
--cc=mhiramat@kernel.org \
--cc=palmer@rivosinc.com \
--cc=paulmck@kernel.org \
--cc=peterz@infradead.org \
--cc=pmladek@suse.com \
--cc=tglx@linutronix.de \
--cc=torvalds@linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).