linux-kernel - Re: [PATCH] Code clean up for percpu

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Date:	Tue, 11 Oct 2011 09:13:14 -0500 (CDT)
From:	Christoph Lameter <cl@...two.org>
To:	"Alex,Shi" <alex.shi@...el.com>
cc:	"tj@...nel.org" <tj@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"eric.dumazet@...il.com" <eric.dumazet@...il.com>,
	"Huang, Ying" <ying.huang@...el.com>
Subject: Re: [PATCH] Code clean up for percpu_xxx() functions

On Tue, 11 Oct 2011, Alex,Shi wrote:

> percpu_read() used in asm/percpu.h yet. Anyway, I removed definitions
> here and do a work around for the function as following:
>
> @@ -551,7 +544,11 @@ static __always_inline int x86_this_cpu_constant_test_bit(unsigned int nr,
>  {
>         unsigned long __percpu *a = (unsigned long *)addr + nr / BITS_PER_LONG;
>
> -       return ((1UL << (nr % BITS_PER_LONG)) & percpu_read(*a)) != 0;
> +#ifdef CONFIG_X86_64
> +       return ((1UL << (nr % BITS_PER_LONG)) & this_cpu_read_8(*a)) != 0;
> +#else
> +       return ((1UL << (nr % BITS_PER_LONG)) & this_cpu_read_4(*a)) != 0;
> +#endif

OK that looks okay.

> Signed-off-by: Alex Shi <alex.shi@...el.com>

Is this a revised patch? I do not see a use of the __this_cpu_xx ops.

> -#define percpu_write(var, val)		percpu_to_op("mov", var, val)
> -#define percpu_add(var, val)		percpu_add_op(var, val)
> -#define percpu_sub(var, val)		percpu_add_op(var, -(val))
> -#define percpu_and(var, val)		percpu_to_op("and", var, val)
> -#define percpu_or(var, val)		percpu_to_op("or", var, val)
> -#define percpu_xor(var, val)		percpu_to_op("xor", var, val)
> -#define percpu_inc(var)		percpu_unary_op("inc", var)
> +#define this_cpu_read_stable(var)	percpu_from_op("mov", var, "p" (&(var)))
> +#define this_cpu_inc(var)		percpu_unary_op("inc", var)

Why redefine this_cpu_inc? include/linux/percpu.h already defines it.

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