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Date: Thu, 30 Jan 2014 19:05:33 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Will Deacon <will.deacon@arm.com>
Cc: Waiman Long <Waiman.Long@hp.com>, Thomas Gleixner <tglx@linutronix.de>,
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        Andrew Morton <akpm@linux-foundation.org>,
        Michel Lespinasse <walken@google.com>,
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        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
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        Scott J Norton <scott.norton@hp.com>,
        "will@willdeacon.co.uk" <will@willdeacon.co.uk>
Subject: Re: [PATCH v11 0/4] Introducing a queue read/write lock
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On Thu, Jan 30, 2014 at 05:52:12PM +0000, Will Deacon wrote:
> It would be nice if these were default implementations of the unlock, then
> architectures just implement atomic_sub_release how they like.

Yes, I suppose that makes sense. Last time I proposed the primitive
nobody yelled at me, so I suppose that means people agree :-)

> One thing worth mentioning: I have a fairly invasive set of changes pending
> for arch/arm64/include/asm/atomic.h, so if you do decide to go with this,
> I'm more than happy to take the sub_release part via the arm64 tree. I guess
> it depends on when this is likely to get merged.

I suppose it depends on when I get enough courage to do: vim
arch/*/include/asm/atomic*.h :-)

There's a few other cleanups I want to do, like today I found
atomic_{set,clear}_mask() instead of the more natural atomic_{or,and}()
functions.

I also think we can get rid of the {inc,dec} variants of
smp_mb__{before,after}_atomic() since these barriers should be the same
for _all_ atomic ops that do not already imply full mb semantics, and
they're certainly the same for all current inc/dec.

If tomorrow is another slow day and I get through enough of the review
backlog I might just give it a go.

Anyway, I'll base them on your arm64 changes, I know where to find
those.