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percpu: Generic support for this_cpu_cmpxchg_double()
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Introduce this_cpu_cmpxchg_double().  this_cpu_cmpxchg_double() allows
the comparison between two consecutive words and replaces them if
there is 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!

-tj: Updated to return bool instead of int, converted size check to
     BUILD_BUG_ON() instead of VM_BUG_ON() and other cosmetic changes.

Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Christoph Lameter authored and Tejun Heo committed Feb 28, 2011
1 parent 0f06c06 commit 7c33433
Showing 1 changed file with 128 additions and 0 deletions.
128 changes: 128 additions & 0 deletions include/linux/percpu.h
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Original file line number Diff line number Diff line change
Expand Up @@ -255,6 +255,30 @@ extern void __bad_size_call_parameter(void);
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_bool(stem, pcp1, pcp2, ...) \
({ \
bool pdcrb_ret__; \
__verify_pcpu_ptr(&pcp1); \
BUILD_BUG_ON(sizeof(pcp1) != sizeof(pcp2)); \
VM_BUG_ON((unsigned long)(&pcp1) % (2 * sizeof(pcp1))); \
VM_BUG_ON((unsigned long)(&pcp2) != \
(unsigned long)(&pcp1) + sizeof(pcp1)); \
switch(sizeof(pcp1)) { \
case 1: pdcrb_ret__ = stem##1(pcp1, pcp2, __VA_ARGS__); break; \
case 2: pdcrb_ret__ = stem##2(pcp1, pcp2, __VA_ARGS__); break; \
case 4: pdcrb_ret__ = stem##4(pcp1, pcp2, __VA_ARGS__); break; \
case 8: pdcrb_ret__ = stem##8(pcp1, pcp2, __VA_ARGS__); break; \
default: \
__bad_size_call_parameter(); break; \
} \
pdcrb_ret__; \
})

#define __pcpu_size_call(stem, variable, ...) \
do { \
__verify_pcpu_ptr(&(variable)); \
Expand Down Expand Up @@ -500,6 +524,45 @@ do { \
__pcpu_size_call_return2(this_cpu_cmpxchg_, pcp, oval, nval)
#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__; \
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_bool(this_cpu_cmpxchg_double_, (pcp1), (pcp2), (oval1), (oval2), (nval1), (nval2))
#endif

/*
* Generic percpu operations that do not require preemption handling.
* Either we do not care about races or the caller has the
Expand Down Expand Up @@ -703,6 +766,39 @@ do { \
__pcpu_size_call_return2(__this_cpu_cmpxchg_, pcp, oval, nval)
#endif

#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_bool(__this_cpu_cmpxchg_double_, (pcp1), (pcp2), (oval1), (oval2), (nval1), (nval2))
#endif

/*
* IRQ safe versions of the per cpu RMW operations. Note that these operations
* are *not* safe against modification of the same variable from another
Expand Down Expand Up @@ -823,4 +919,36 @@ 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 */

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