All of lore.kernel.org
 help / color / mirror / Atom feed
From: Will Deacon <will@kernel.org>
To: Rui Wang <wangrui@loongson.cn>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>, Arnd Bergmann <arnd@arndb.de>,
	Waiman Long <longman@redhat.com>,
	Boqun Feng <boqun.feng@gmail.com>, Guo Ren <guoren@kernel.org>,
	linux-arch@vger.kernel.org, hev <r@hev.cc>,
	Xuefeng Li <lixuefeng@loongson.cn>,
	Huacai Chen <chenhuacai@gmail.com>,
	Jiaxun Yang <jiaxun.yang@flygoat.com>,
	Huacai Chen <chenhuacai@loongson.cn>
Subject: Re: [RFC PATCH v1 1/5] locking/atomic: Implement atomic_fetch_and_or
Date: Thu, 29 Jul 2021 10:39:23 +0100	[thread overview]
Message-ID: <20210729093923.GD21151@willie-the-truck> (raw)
In-Reply-To: <20210728114822.1243-1-wangrui@loongson.cn>

On Wed, Jul 28, 2021 at 07:48:22PM +0800, Rui Wang wrote:
> From: wangrui <wangrui@loongson.cn>
> 
> This patch introduce a new atomic primitive 'and_or', It may be have three
> types of implemeations:
> 
>  * The generic implementation is based on arch_cmpxchg.
>  * The hardware supports atomic 'and_or' of single instruction.

Do any architectures actually support this instruction?

On arm64, we can clear arbitrary bits and we can set arbitrary bits, but we
can't combine the two in a fashion which provides atomicity and
forward-progress guarantees.

Please can you explain how this new primitive will be used, in case there's
an alternative way of doing it which maps better to what CPUs can actually
do?

Cheers,

Will

  parent reply	other threads:[~2021-07-29  9:39 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-28 11:48 [RFC PATCH v1 1/5] locking/atomic: Implement atomic_fetch_and_or Rui Wang
2021-07-28 12:14 ` Boqun Feng
2021-07-28 14:12   ` Hev
2021-07-28 12:58 ` Peter Zijlstra
2021-07-28 13:00   ` Peter Zijlstra
2021-07-28 13:16   ` Peter Zijlstra
2021-07-28 13:21     ` Peter Zijlstra
2021-07-29  1:58       ` hev
2021-07-29  8:23         ` Peter Zijlstra
2021-07-29  8:37           ` hev
2021-07-29  9:39 ` Will Deacon [this message]
2021-07-29 10:18   ` hev
2021-07-29 12:52     ` Will Deacon
2021-07-30 18:40     ` Waiman Long
2021-07-31  1:46       ` hev
2021-08-05 13:20       ` Huacai Chen
2021-08-09 11:37 ` Geert Uytterhoeven

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=20210729093923.GD21151@willie-the-truck \
    --to=will@kernel.org \
    --cc=arnd@arndb.de \
    --cc=boqun.feng@gmail.com \
    --cc=chenhuacai@gmail.com \
    --cc=chenhuacai@loongson.cn \
    --cc=guoren@kernel.org \
    --cc=jiaxun.yang@flygoat.com \
    --cc=linux-arch@vger.kernel.org \
    --cc=lixuefeng@loongson.cn \
    --cc=longman@redhat.com \
    --cc=mingo@redhat.com \
    --cc=peterz@infradead.org \
    --cc=r@hev.cc \
    --cc=wangrui@loongson.cn \
    /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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.