linux-kernel - Re: [RFC][PATCH 10/31] locking,hexagon: Implement atomic_fetch

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Message-ID: <20160423021658.GX3430@twins.programming.kicks-ass.net>
Date:	Sat, 23 Apr 2016 04:16:58 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	torvalds@...ux-foundation.org, mingo@...nel.org,
	tglx@...utronix.de, will.deacon@....com,
	paulmck@...ux.vnet.ibm.com, boqun.feng@...il.com,
	waiman.long@....com, fweisbec@...il.com
Cc:	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	rth@...ddle.net, vgupta@...opsys.com, linux@....linux.org.uk,
	egtvedt@...fundet.no, realmz6@...il.com,
	ysato@...rs.sourceforge.jp, rkuo@...eaurora.org,
	tony.luck@...el.com, geert@...ux-m68k.org, james.hogan@...tec.com,
	ralf@...ux-mips.org, dhowells@...hat.com, jejb@...isc-linux.org,
	mpe@...erman.id.au, schwidefsky@...ibm.com, dalias@...c.org,
	davem@...emloft.net, cmetcalf@...lanox.com, jcmvbkbc@...il.com,
	arnd@...db.de, dbueso@...e.de, fengguang.wu@...el.com
Subject: Re: [RFC][PATCH 10/31] locking,hexagon: Implement
 atomic_fetch_{add,sub,and,or,xor}()

On Fri, Apr 22, 2016 at 11:04:23AM +0200, Peter Zijlstra wrote:
> +#define ATOMIC_FETCH_OP(op)						\
> +static inline int atomic_fetch_##op(int i, atomic_t *v)			\
> +{									\
> +	int output, val;						\
> +									\
> +	__asm__ __volatile__ (						\
> +		"1:	%0 = memw_locked(%2);\n"			\
> +		"	%1 = "#op "(%0,%3);\n"				\
> +		"	memw_locked(%2,P3)=%0;\n"			\

I'm thinking that wants to be:

			memw_locked(%2,P3)=%1;

> +		"	if !P3 jump 1b;\n"				\
> +		: "=&r" (output), "=&r" (val)				\
> +		: "r" (&v->counter), "r" (i)				\
> +		: "memory", "p3"					\
> +	);								\
> +	return output;							\
> +}