linux-kernel - Re: [PATCH 1/5] asm-generic: Add _{relaxed|acquire|release}() variants for inc/dec atomics

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Message-ID: <20151006090152.GA10492@arm.com>
Date:	Tue, 6 Oct 2015 10:01:52 +0100
From:	Will Deacon <will.deacon@....com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Davidlohr Bueso <dave@...olabs.net>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Paul E.McKenney" <paulmck@...ux.vnet.ibm.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH 1/5] asm-generic: Add _{relaxed|acquire|release}()
 variants for inc/dec atomics

On Mon, Oct 05, 2015 at 09:48:24PM +0200, Peter Zijlstra wrote:
> On Mon, Oct 05, 2015 at 06:32:43PM +0100, Will Deacon wrote:
> > On Thu, Oct 01, 2015 at 07:39:10AM +0100, Peter Zijlstra wrote:
> > > On Wed, Sep 30, 2015 at 01:03:11PM -0700, Davidlohr Bueso wrote:
> > > > Similar to what we have for regular add/sub calls. For now, no actual arch
> > > > implements them, so everyone falls back to the default atomics... iow,
> > > > nothing changes. These will be used in future primitives.
> > > > 
> > > 
> > > Maybe also do an aargh64 patch for this?
> > 
> > I can follow up with that, since I'm about 60% through adding the
> > relaxed/acquire/release versions of all the other primitives. It's a fair
> > amount of work thanks to the new atomic instructions making me do everything
> > twice... (that and I've been on holiday this past week!)
> 
> Right, what I meant was arm (I thought argh64 was the one with _relaxed
> bits in, but my memories tricked me, it was ARM).
> 
> If you add new _relaxed ops, we'd better convert all archs that support
> _relaxed, which would be ARM (for now).

Right, yeah, arch/arm/ will need updating along with this series. Should
be straightforward to implement them in terms of atomic_{add,sub}_*.

Will
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