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Date: Fri, 25 Feb 2011 13:25:57 -0500
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Christoph Lameter <cl@...ux.com>
Cc: Tejun Heo <tj@...nel.org>, akpm@...ux-foundation.org,
Pekka Enberg <penberg@...helsinki.fi>,
linux-kernel@...r.kernel.org,
Eric Dumazet <eric.dumazet@...il.com>,
"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [cpuops cmpxchg double V3 3/5] Generic support for
this_cpu_cmpxchg_double
* Christoph Lameter (cl@...ux.com) wrote:
> Introduce this_cpu_cmpxchg_double. this_cpu_cmpxchg_double() allows the
> comparision between two consecutive words and replaces them if there is
comparison
/nitpick again ;)
Mathieu
> a match.
>
> bool this_cpu_cmpxchg_double(pcp1, pcp2,
> old_word1, old_word2, new_word1, new_word2)
>
> this_cpu_cmpxchg_double does not return the old value (difficult since
> there are two words) but a boolean indicating if the operation was
> successful.
>
> The first percpu variable must be double word aligned!
>
> Signed-off-by: Christoph Lameter <cl@...ux.com>
>
> ---
> include/linux/percpu.h | 130 +++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 130 insertions(+)
>
> Index: linux-2.6/include/linux/percpu.h
> ===================================================================
> --- linux-2.6.orig/include/linux/percpu.h 2011-01-10 10:22:35.000000000 -0600
> +++ linux-2.6/include/linux/percpu.h 2011-01-10 10:26:43.000000000 -0600
> @@ -255,6 +255,29 @@ extern void __bad_size_call_parameter(vo
> pscr2_ret__; \
> })
>
> +/*
> + * Special handling for cmpxchg_double. cmpxchg_double is passed two
> + * percpu variables. The first has to be aligned to a double word
> + * boundary and the second has to follow directly thereafter.
> + */
> +#define __pcpu_double_call_return_int(stem, pcp1, pcp2, ...) \
> +({ \
> + int ret__; \
> + __verify_pcpu_ptr(&pcp1); \
> + VM_BUG_ON((unsigned long)(&pcp1) % (2 * sizeof(pcp1))); \
> + VM_BUG_ON((unsigned long)(&pcp2) != (unsigned long)(&pcp1) + sizeof(pcp1));\
> + VM_BUG_ON(sizeof(pcp1) != sizeof(pcp2)); \
> + switch(sizeof(pcp1)) { \
> + case 1: ret__ = stem##1(pcp1, pcp2, __VA_ARGS__);break; \
> + case 2: ret__ = stem##2(pcp1, pcp2, __VA_ARGS__);break; \
> + case 4: ret__ = stem##4(pcp1, pcp2, __VA_ARGS__);break; \
> + case 8: ret__ = stem##8(pcp1, pcp2, __VA_ARGS__);break; \
> + default: \
> + __bad_size_call_parameter();break; \
> + } \
> + ret__; \
> +})
> +
> #define __pcpu_size_call(stem, variable, ...) \
> do { \
> __verify_pcpu_ptr(&(variable)); \
> @@ -318,6 +341,80 @@ do { \
> # define this_cpu_read(pcp) __pcpu_size_call_return(this_cpu_read_, (pcp))
> #endif
>
> +/*
> + * cmpxchg_double replaces two adjacent scalars at once. The first two
> + * parameters are per cpu variables which have to be of the same size.
> + * A truth value is returned to indicate success or
> + * failure (since a double register result is difficult to handle).
> + * There is very limited hardware support for these operations. So only certain
> + * sizes may work.
> + */
> +#define __this_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2) \
> +({ \
> + int __ret = 0; \
> + if (__this_cpu_read(pcp1) == (oval1) && \
> + __this_cpu_read(pcp2) == (oval2)) { \
> + __this_cpu_write(pcp1, (nval1)); \
> + __this_cpu_write(pcp2, (nval2)); \
> + __ret = 1; \
> + } \
> + (__ret); \
> +})
> +
> +#ifndef __this_cpu_cmpxchg_double
> +# ifndef __this_cpu_cmpxchg_double_1
> +# define __this_cpu_cmpxchg_double_1(pcp1, pcp2, oval1, oval2, nval1, nval2) \
> + __this_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
> +# endif
> +# ifndef __this_cpu_cmpxchg_double_2
> +# define __this_cpu_cmpxchg_double_2(pcp1, pcp2, oval1, oval2, nval1, nval2) \
> + __this_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
> +# endif
> +# ifndef __this_cpu_cmpxchg_double_4
> +# define __this_cpu_cmpxchg_double_4(pcp1, pcp2, oval1, oval2, nval1, nval2) \
> + __this_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
> +# endif
> +# ifndef __this_cpu_cmpxchg_double_8
> +# define __this_cpu_cmpxchg_double_8(pcp1, pcp2, oval1, oval2, nval1, nval2) \
> + __this_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
> +# endif
> +# define __this_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2) \
> + __pcpu_double_call_return_int(__this_cpu_cmpxchg_double_, (pcp1), (pcp2) \
> + oval1, oval2, nval1, nval2)
> +#endif
> +
> +#define _this_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2) \
> +({ \
> + int ret__; \
> + preempt_disable(); \
> + ret__ = __this_cpu_generic_cmpxchg_double(pcp1, pcp2, \
> + oval1, oval2, nval1, nval2); \
> + preempt_enable(); \
> + ret__; \
> +})
> +
> +#ifndef this_cpu_cmpxchg_double
> +# ifndef this_cpu_cmpxchg_double_1
> +# define this_cpu_cmpxchg_double_1(pcp1, pcp2, oval1, oval2, nval1, nval2) \
> + _this_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
> +# endif
> +# ifndef this_cpu_cmpxchg_double_2
> +# define this_cpu_cmpxchg_double_2(pcp1, pcp2, oval1, oval2, nval1, nval2) \
> + _this_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
> +# endif
> +# ifndef this_cpu_cmpxchg_double_4
> +# define this_cpu_cmpxchg_double_4(pcp1, pcp2, oval1, oval2, nval1, nval2) \
> + _this_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
> +# endif
> +# ifndef this_cpu_cmpxchg_double_8
> +# define this_cpu_cmpxchg_double_8(pcp1, pcp2, oval1, oval2, nval1, nval2) \
> + _this_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
> +# endif
> +# define this_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2) \
> + __pcpu_double_call_return_int(this_cpu_cmpxchg_double_, (pcp1), (pcp2), \
> + oval1, oval2, nval1, nval2)
> +#endif
> +
> #define _this_cpu_generic_to_op(pcp, val, op) \
> do { \
> preempt_disable(); \
> @@ -823,4 +920,37 @@ do { \
> __pcpu_size_call_return2(irqsafe_cpu_cmpxchg_, (pcp), oval, nval)
> #endif
>
> +#define irqsafe_generic_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2) \
> +({ \
> + int ret__; \
> + unsigned long flags; \
> + local_irq_save(flags); \
> + ret__ = __this_cpu_generic_cmpxchg_double(pcp1, pcp2, \
> + oval1, oval2, nval1, nval2); \
> + local_irq_restore(flags); \
> + ret__; \
> +})
> +
> +#ifndef irqsafe_cpu_cmpxchg_double
> +# ifndef irqsafe_cpu_cmpxchg_double_1
> +# define irqsafe_cpu_cmpxchg_double_1(pcp1, pcp2, oval1, oval2, nval1, nval2) \
> + irqsafe_generic_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
> +# endif
> +# ifndef irqsafe_cpu_cmpxchg_double_2
> +# define irqsafe_cpu_cmpxchg_double_2(pcp1, pcp2, oval1, oval2, nval1, nval2) \
> + irqsafe_generic_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
> +# endif
> +# ifndef irqsafe_cpu_cmpxchg_double_4
> +# define irqsafe_cpu_cmpxchg_double_4(pcp1, pcp2, oval1, oval2, nval1, nval2) \
> + irqsafe_generic_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
> +# endif
> +# ifndef irqsafe_cpu_cmpxchg_double_8
> +# define irqsafe_cpu_cmpxchg_double_8(pcp1, pcp2, oval1, oval2, nval1, nval2) \
> + irqsafe_generic_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2)
> +# endif
> +# define irqsafe_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2) \
> + __pcpu_double_call_return_int(irqsafe_cpu_cmpxchg_double_, (pcp1), (pcp2), \
> + oval1, oval2, nval1, nval2)
> +#endif
> +
> #endif /* __LINUX_PERCPU_H */
>
--
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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