linux-kernel - Re: [RFC][PATCH 23/24] atomic: Collapse all atomic_{set,clear}

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Date:	Fri, 10 Jul 2015 09:13:58 +0000
From:	Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Peter Zijlstra <peterz@...radead.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux-Arch <linux-arch@...r.kernel.org>,
	Richard Henderson <rth@...ddle.net>,
	"Russell King" <linux@....linux.org.uk>,
	Will Deacon <will.deacon@....com>,
	Håvard Skinnemoen <hskinnemoen@...il.com>,
	Miao Steven <realmz6@...il.com>,
	David Howells <dhowells@...hat.com>,
	Richard Kuo <rkuo@...eaurora.org>,
	Tony Luck <tony.luck@...el.com>,
	James Hogan <james.hogan@...tec.com>,
	Ralf Baechle <ralf@...ux-mips.org>,
	"James E.J. Bottomley" <jejb@...isc-linux.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	"David S. Miller" <davem@...emloft.net>,
	Chris Metcalf <cmetcalf@...hip.com>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [RFC][PATCH 23/24] atomic: Collapse all atomic_{set,clear}_mask
 definitions

On Friday 10 July 2015 02:40 PM, Geert Uytterhoeven wrote:
> Hi Peter,
>
> On Thu, Jul 9, 2015 at 7:29 PM, Peter Zijlstra <peterz@...radead.org> wrote:
>> > --- a/include/linux/atomic.h
>> > +++ b/include/linux/atomic.h
>> > @@ -28,6 +28,23 @@ static inline int atomic_add_unless(atom
>> >  #define atomic_inc_not_zero(v)         atomic_add_unless((v), 1, 0)
>> >  #endif
>> >
>> > +#ifndef atomic_nand
>> > +static inline void atomic_nand(int i, atomic_t *v)
>> > +{
>> > +       atomic_and(~i, v);
> That sounds like a misnomer...
>
> Your NAND is "A & ~B", while my[*] NAND is "~(A & B)"?
>
> [*] https://en.wikipedia.org/wiki/NAND_logic
>
> What about atomic_clear()? (Is atomic_bic() too ARM-centric?)
>

ARM + ARC centric :-)

We have the BIC instruction as well which does the same: A & ~B

-Vineet
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