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

From: Will Deacon <will.deacon@arm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>,
	Ingo Molnar <mingo@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	"Paul E.McKenney" <paulmck@linux.vnet.ibm.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Davidlohr Bueso <dbueso@suse.de>
Subject: Re: [PATCH 1/5] asm-generic: Add _{relaxed|acquire|release}() variants for inc/dec atomics
Date: Tue, 6 Oct 2015 10:01:52 +0100	[thread overview]
Message-ID: <20151006090152.GA10492@arm.com> (raw)
In-Reply-To: <20151005194824.GF3816@twins.programming.kicks-ass.net>

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