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Date: Wed, 16 Mar 2016 09:04:37 +0100
From: Ingo Molnar <mingo@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
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        Thomas Gleixner <tglx@linutronix.de>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v2] atomic: Fix bugs in 'fetch_or()' and rename it to
 'xchg_or()'
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* Peter Zijlstra <peterz@infradead.org> wrote:

> On Tue, Mar 15, 2016 at 01:21:45PM +0100, Ingo Molnar wrote:
> >  - Renaming fetch_or() to xchg_or(), recognizing that the semantics
> >    are xchg()-alike.
> 
> Let me add another argument for why I don't like the "exchange/swap
> (and) add" naming.
> 
> Exchange (and swap) replace one value for another, like:
> 
> 	old = xchg(ptr, val);
> 
> Whatever was there, gets replaced by the independent value in @val.
> Straight up replacement.
> 
> However with something like xchg_or, you don't do a direct replacement
> with an unrelated value. Instead you modify the pre-existing value. So
> there really isn't an exchange at all.
> 
> So "fetch (and) or" really describes the operation better. You load
> (fetch) the value and then modify it, in an indivisible (aka atomic)
> fashion.

Ok!

Could we at least somehow sneak the notion of 'atomicity' into it?

	fetch_or()
	fetch_and()
	fetch_not()

vs.

	fetch_atomic_or()
	fetch_atomic_and()
	fetch_atomic_not()

vs.

	atomic_fetch_or()
	atomic_fetch_and()
	atomic_fetch_not()

?

Thanks,

	Ingo