From: David Howells <dhowells@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: dhowells@redhat.com,
Andrea Parri <andrea.parri@amarulasolutions.com>,
linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
Alan Stern <stern@rowland.harvard.edu>,
Will Deacon <will.deacon@arm.com>,
Boqun Feng <boqun.feng@gmail.com>,
Nicholas Piggin <npiggin@gmail.com>,
Jade Alglave <j.alglave@ucl.ac.uk>,
Luc Maranget <luc.maranget@inria.fr>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Akira Yokosawa <akiyks@gmail.com>,
Daniel Lustig <dlustig@nvidia.com>,
Jonathan Corbet <corbet@lwn.net>, Ingo Molnar <mingo@redhat.com>,
Randy Dunlap <rdunlap@infradead.org>
Subject: Re: [PATCH] doc: Update wake_up() & co. memory-barrier guarantees
Date: Mon, 25 Jun 2018 13:12:45 +0100 [thread overview]
Message-ID: <2779.1529928765@warthog.procyon.org.uk> (raw)
In-Reply-To: <20180625095031.GX2494@hirez.programming.kicks-ass.net>
Peter Zijlstra <peterz@infradead.org> wrote:
> So yes, I suppose we're entirely suck with the full memory barrier
> semantics like that. But I still find it easier to think of it like a
> RELEASE that pairs with the ACQUIRE of waking up, such that the task
> is guaranteed to observe it's own wake condition.
>
> And maybe that is the thing I'm missing here. These comments only state
> that it does in fact imply a full memory barrier, but do not explain
> why, should it?
I think because RELEASE and ACQUIRE concepts didn't really exist in Linux at
the time I wrote the doc, so the choices were read/readdep, write or full.
Since this document defines the *minimum* you can expect rather than what the
kernel actually gives you, I think it probably makes sense to switch to
RELEASE and ACQUIRE here.
David
next prev parent reply other threads:[~2018-06-25 12:12 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-25 9:17 [PATCH] doc: Update wake_up() & co. memory-barrier guarantees Andrea Parri
2018-06-25 9:50 ` Peter Zijlstra
2018-06-25 10:56 ` Andrea Parri
2018-06-25 12:31 ` Peter Zijlstra
2018-06-25 13:16 ` Andrea Parri
2018-06-25 14:18 ` Peter Zijlstra
2018-06-25 14:56 ` Andrea Parri
2018-06-25 15:44 ` Daniel Lustig
2018-06-25 16:38 ` Peter Zijlstra
2018-06-25 16:37 ` Peter Zijlstra
2018-06-26 10:09 ` Andrea Parri
2018-06-26 15:30 ` Peter Zijlstra
2018-06-27 14:15 ` Andrea Parri
2018-06-25 12:12 ` David Howells [this message]
2018-06-25 12:28 ` Andrea Parri
2018-06-25 13:00 ` Peter Zijlstra
2018-06-25 16:56 ` Alan Stern
2018-06-26 10:11 ` Andrea Parri
2018-06-26 13:49 ` Alan Stern
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