linux-kernel - Re: [RFC][PATCH 5/7] jump_label: atomic

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Date:	Fri, 15 Oct 2010 16:01:39 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Ingo Molnar <mingo@...e.hu>, Jason Baron <jbaron@...hat.com>,
	linux-kernel@...r.kernel.org, David Miller <davem@...emloft.net>,
	Mike Galbraith <efault@....de>
Subject: Re: [RFC][PATCH 5/7] jump_label: atomic_t interface

On Thu, Oct 14, 2010 at 10:34:09PM +0200, Peter Zijlstra wrote:
> Add an interface to allow usage of jump_labels with atomic counters
> 
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> ---
>  include/linux/jump_label_ref.h |   44 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 44 insertions(+)
> 
> Index: linux-2.6/include/linux/jump_label_ref.h
> ===================================================================
> --- /dev/null
> +++ linux-2.6/include/linux/jump_label_ref.h
> @@ -0,0 +1,44 @@
> +#ifndef _LINUX_JUMP_LABEL_REF_H
> +#define _LINUX_JUMP_LABEL_REF_H
> +
> +#include <linux/jump_label.h>
> +#include <asm/atomic.h>
> +
> +#ifdef HAVE_JUMP_LABEL
> +
> +static inline void jump_label_inc(atomic_t *key)
> +{
> +	if (atomic_add_return(1, key) == 1)
> +		jump_label_enable(key);
> +}
> +
> +static inline void jump_label_dec(atomic_t *key)
> +{
> +	if (atomic_dec_and_test(key))
> +		jump_label_disable(key);
> +}



Nice. I was trying to find a more self-explanatory name,
like jump_label_get/put or jump_label_inc_enable/jump_label_dec_disable.

But in fact the current name looks good eventually.

Acked-by: Frederic Weisbecker <fweisbec@...il.com>




> +#else /* !HAVE_JUMP_LABEL */
> +
> +static inline void jump_label_inc(atomic_t *key)
> +{
> +	atomic_inc(key);
> +}
> +
> +static inline void jump_label_dec(atomic_t *key)
> +{
> +	atomic_dec(key);
> +}
> +
> +#undef JUMP_LABEL
> +#define JUMP_LABEL(key, label)						\
> +do {									\
> +	if (unlikely(__builtin_choose_expr(				\
> +	      __builtin_types_compatible_p(typeof(key), atomic_t *),	\
> +	      atomic_read((atomic_t *)(key)), *(key))))			\
> +		goto label;						\
> +} while (0)
> +
> +#endif /* HAVE_JUMP_LABEL */
> +
> +#endif /* _LINUX_JUMP_LABEL_REF_H */
> 
> 

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