stable.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Tejun Heo <tj@kernel.org>
To: Aleksa Sarai <cyphar@cyphar.com>
Cc: Li Zefan <lizefan@huawei.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
	stable@vger.kernel.org
Subject: Re: [PATCH] cgroup: pids: use {READ,WRITE}_ONCE for pids->limit operations
Date: Wed, 16 Oct 2019 08:54:07 -0700	[thread overview]
Message-ID: <20191016155407.GP18794@devbig004.ftw2.facebook.com> (raw)
In-Reply-To: <20191016153520.zet5mn5xsygig4xc@yavin.dot.cyphar.com>

On Thu, Oct 17, 2019 at 02:35:20AM +1100, Aleksa Sarai wrote:
> > Sure, I will switch it to use atomic64_read() and atomic64_set() instead
> > if that's what you'd prefer. Though I will mention that on quite a few
> > architectures atomic64_read() is defined as:
> > 
> >   #define atomic64_read(v)        READ_ONCE((v)->counter)
> 
> Though I guess that's because on those architectures it turns out that
> READ_ONCE is properly atomic?

Oh yeah, on archs where 64bit accesses are atomic, READ_ONCE() /
WRITE_ONCE() would work here.  If the limit variable were ulong
instead of an explicit 64bit variable, RW ONCE would work too as ulong
accesses are atomic on all archs IIRC.

Thanks.

-- 
tejun

      reply	other threads:[~2019-10-16 15:54 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-12  1:05 [PATCH] cgroup: pids: use {READ,WRITE}_ONCE for pids->limit operations Aleksa Sarai
2019-10-14 15:41 ` Tejun Heo
2019-10-14 15:59   ` Aleksa Sarai
2019-10-14 16:33     ` Tejun Heo
2019-10-16  8:32       ` Aleksa Sarai
2019-10-16 14:27         ` Tejun Heo
2019-10-16 15:29           ` Aleksa Sarai
2019-10-16 15:32             ` Tejun Heo
2019-10-16 15:35             ` Aleksa Sarai
2019-10-16 15:54               ` Tejun Heo [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=20191016155407.GP18794@devbig004.ftw2.facebook.com \
    --to=tj@kernel.org \
    --cc=cgroups@vger.kernel.org \
    --cc=cyphar@cyphar.com \
    --cc=hannes@cmpxchg.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=lizefan@huawei.com \
    --cc=stable@vger.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;
as well as URLs for NNTP newsgroup(s).