linux-kernel - Re: [PATCH memory-barriers.txt 2/7] documentation: Fix missed renaming: s/lock/acquire

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Message-ID: <20160413142917.GB3614@linux.vnet.ibm.com>
Date:	Wed, 13 Apr 2016 07:29:17 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel@...r.kernel.org, mingo@...nel.org,
	jiangshanlai@...il.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
	josh@...htriplett.org, tglx@...utronix.de, rostedt@...dmis.org,
	dhowells@...hat.com, edumazet@...gle.com, dvhart@...ux.intel.com,
	fweisbec@...il.com, oleg@...hat.com, bobby.prani@...il.com,
	SeongJae Park <sj38.park@...il.com>
Subject: Re: [PATCH memory-barriers.txt 2/7] documentation: Fix missed
 renaming: s/lock/acquire

On Wed, Apr 13, 2016 at 02:46:51PM +0200, Peter Zijlstra wrote:
> On Tue, Apr 12, 2016 at 08:52:50AM -0700, Paul E. McKenney wrote:
> > From: SeongJae Park <sj38.park@...il.com>
> > 
> > Terms `lock` and `unlock` have changed to `acquire` / `release` by
> > commit 2e4f5382d12a441b5cccfdde00308df15c2ce300 ("locking/doc: Rename
> > LOCK/UNLOCK to ACQUIRE/RELEASE").  However, the commit missed to change
> > the table of content.  This commit changes the missed parts.
> > Also, section name `Acquiring functions` is not appropriate for the
> > section because the section is saying about lock in actual.  This commit
> > changes the name to more appropriate name, `Lock acquisition functions`.
> 
> True, because of this ppc thing :/
> 
> If we get PPC to switch to RCsc locks, there actually is a difference
> again.

On that, I must defer to Michael Ellerman.

> Given the current state I'm not sure how much we should care, but
> there's a fundamental difference between things like load-acquire and
> acquiring a lock, in that the lock-acquire must also very much imply a
> store.

Agreed, even given PPC's current lock implementation, load-acquire
and lock-acquire are at best similar, not identical.  That said, one
strong similarity is the effect on ordering.

> In any case, these are jet-lagged ramblings, feel free to ignore :-)

I think we went in opposite directions.  I was in UK last week.  ;-)

							Thanx, Paul