linux-kernel - Re: [PATCH v2 1/7] atomics: add acquire/release/relaxed variants of some atomic operations

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Date:	Fri, 17 Jul 2015 10:40:14 +0100
From:	Will Deacon <will.deacon@....com>
To:	Waiman Long <waiman.long@...com>
Cc:	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	"peterz@...radead.org" <peterz@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"paulmck@...ux.vnet.ibm.com" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH v2 1/7] atomics: add acquire/release/relaxed variants of
 some atomic operations

Hi Waiman,

On Fri, Jul 17, 2015 at 01:07:28AM +0100, Waiman Long wrote:
> On 07/16/2015 11:32 AM, Will Deacon wrote:
> > +#ifndef atomic64_add_return_relaxed
> > +#define  atomic64_add_return_relaxed	atomic64_add_return
> > +#define  atomic64_add_return_acquire	atomic64_add_return
> > +#define  atomic64_add_return_release	atomic64_add_return
> > +
> > +#else /* atomic64_add_return_relaxed */
> > +
> > +#ifndef atomic64_add_return_acquire
> > +#define  atomic64_add_return_acquire(...)				\
> > +	__atomic_op_acquire(long long, atomic64_add_return, __VA_ARGS__)
> > +#endif
> > +
> > +#ifndef atomic64_add_return_release
> > +#define  atomic64_add_return_release(...)				\
> > +	__atomic_op_release(long long, atomic64_add_return, __VA_ARGS__)
> > +#endif
> > +
> > +#ifndef atomic64_add_return
> > +#define  atomic64_add_return(...)					\
> > +	__atomic_op_fence(long long, atomic64_add_return, __VA_ARGS__)
> > +#endif
> > +#endif /* atomic64_add_return_relaxed */
> > +
> 
> I have a minor nit. The atomic_add_return block is repeated with 
> "s/atomic_add_return/.../". Perhaps some more comments to delineate the 
> blocks more visibly will make this patch easier to read.

Yeah, I agree that it's pretty hard going, but I don't have any great
suggestions to solve that. I could add an extra blank line + comment
before the start of each section, if you like? Example snippet below.

Will

--->8

[...]
#endif /* atomic_sub_return_relaxed */


/* atomic_xchg_relaxed */
#ifndef atomic_xchg_relaxed
#define  atomic_xchg_relaxed		atomic_xchg
#define  atomic_xchg_acquire		atomic_xchg
#define  atomic_xchg_release		atomic_xchg

#else /* atomic_xchg_relaxed */

#ifndef atomic_xchg_acquire
#define  atomic_xchg_acquire(...)					\
	__atomic_op_acquire(int, atomic_xchg, __VA_ARGS__)
#endif

#ifndef atomic_xchg_release
#define  atomic_xchg_release(...)					\
	__atomic_op_release(int, atomic_xchg, __VA_ARGS__)
#endif

#ifndef atomic_xchg
#define  atomic_xchg(...)						\
	__atomic_op_fence(int, atomic_xchg, __VA_ARGS__)
#endif
#endif /* atomic_xchg_relaxed */


/* atomic_cmpxchg_relaxed */
[...]
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