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Message-ID: <25e057c00901150559t14fd3becn5cea005895dacdc4@mail.gmail.com>
Date: Thu, 15 Jan 2009 14:59:35 +0100
From: "roel kluin" <roel.kluin@gmail.com>
To: "Tejun Heo" <tj@kernel.org>
Subject: Re: [patch] add optimized generic percpu accessors
Cc: "Ingo Molnar" <mingo@elte.hu>, "H. Peter Anvin" <hpa@zytor.com>,
       "Brian Gerst" <brgerst@gmail.com>, ebiederm@xmission.com,
       cl@linux-foundation.org, rusty@rustcorp.com.au, travis@sgi.com,
       linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
       steiner@sgi.com, hugh@veritas.com
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	 <20090114093834.GA19799@elte.hu> <496F0F50.6070200@kernel.org>
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> +#ifndef percpu_read
> +# define percpu_read(var)                                              \
> +  ({                                                                   \
> +       typeof(per_cpu_var(var)) __tmp_var__;                           \
> +       __tmp_var__ = get_cpu_var(var);                                 \
> +       put_cpu_var(var);                                               \
> +       __tmp_var__;                                                    \
> +  })
> +#endif

I'm sorry for your eyes, but since var occurs twice, isn't it better to do:

# define percpu_read(var)                                              \
  ({                                                                   \
       typeof(var) __pcpu_read_var__ = var;
               \
       typeof(per_cpu_var(__pcpu_read_var__)) __tmp_var__;                    \
       __tmp_var__ = get_cpu_var(__pcpu_read_var__);                           \
       put_cpu_var(__pcpu_read_var__);                                         \
       __tmp_var__;                                                    \
  })

> +
> +#define __percpu_generic_to_op(var, val, op)                           \
> +do {                                                                   \
> +       get_cpu_var(var) op val;                                        \
> +       put_cpu_var(var);                                               \
> +} while (0)

and:

#define __percpu_generic_to_op(var, val, op)                           \
do {                                                                   \
       typeof(var) __pcpu_gto_var__ = var;
              \
       get_cpu_var(__pcpu_gto_var__) op val;
             \
       put_cpu_var(__pcpu_gto_var__);
             \
} while (0)
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