All of lore.kernel.org
 help / color / mirror / Atom feed
From: Andrea Parri <andrea.parri@amarulasolutions.com>
To: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>
Cc: linux-kernel@vger.kernel.org
Subject: [Question] atomic_fetch_andnot() in nohz_idle_balance()
Date: Wed, 21 Nov 2018 23:34:53 +0100	[thread overview]
Message-ID: <20181121223453.GA4016@andrea> (raw)

Hi,

The comment for the atomic_fetch_andnot() in nohz_idle_balance() says:

  "barrier, pairs with nohz_balance_enter_idle(), ensures ..."

which, well, does sound a note of warning... ;-)

I see that nohz_balance_enter_idle() has an smp_mb__after_atomic() but
the comment for the latter suggests that this barrier is pairing with
the smp_mb() in _nohz_idle_balance().

So, what is the intended pairing barrier for the atomic_fetch_andnot()?
what (which memory accesses) do you want "to order" here?

Thanks,
  Andrea

             reply	other threads:[~2018-11-21 22:35 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-21 22:34 Andrea Parri [this message]
2018-11-26  9:30 ` [Question] atomic_fetch_andnot() in nohz_idle_balance() Peter Zijlstra
2018-11-26 11:37   ` Vincent Guittot
2018-11-26 20:44     ` Andrea Parri
2018-11-27  9:01       ` Vincent Guittot
2018-11-27 10:59         ` Andrea Parri

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=20181121223453.GA4016@andrea \
    --to=andrea.parri@amarulasolutions.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=peterz@infradead.org \
    --cc=vincent.guittot@linaro.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 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.