From: David Laight <David.Laight@ACULAB.COM>
To: 'Arnd Bergmann' <arnd@kernel.org>, Will Deacon <will@kernel.org>,
"Peter Zijlstra" <peterz@infradead.org>,
Arnd Bergmann <arnd@arndb.de>, Matt Evans <mev@rivosinc.com>
Cc: Boqun Feng <boqun.feng@gmail.com>,
Mark Rutland <mark.rutland@arm.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>
Subject: RE: [PATCH] asm-generic: avoid __generic_cmpxchg_local warnings
Date: Thu, 2 Mar 2023 16:40:00 +0000 [thread overview]
Message-ID: <60996fd3604b403ab67e8f73854264ee@AcuMS.aculab.com> (raw)
In-Reply-To: <20230302090032.3740505-1-arnd@kernel.org>
...
> I had another look at why the cast is even needed for atomic_cmpxchg(),
> and as Matt describes the problem here is that atomic_t contains a
> signed 'int', but cmpxchg() takes an 'unsigned long' argument, and
> converting between the two leads to a 64-bit sign-extension of
> negative 32-bit atomics.
How about:
signed_var + 0u + 0ull;
Converts 32bit signed to 64bit unsigned without sign extension.
Compiler will throw it all away if not needed.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
prev parent reply other threads:[~2023-03-02 16:40 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-02 9:00 Arnd Bergmann
2023-03-02 16:40 ` David Laight [this message]
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=60996fd3604b403ab67e8f73854264ee@AcuMS.aculab.com \
--to=david.laight@aculab.com \
--cc=arnd@arndb.de \
--cc=arnd@kernel.org \
--cc=boqun.feng@gmail.com \
--cc=linux-arch@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mark.rutland@arm.com \
--cc=mev@rivosinc.com \
--cc=peterz@infradead.org \
--cc=will@kernel.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
all inboxes | Powered by JetHome®