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Release 4.12 include/linux/percpu-defs.h

Directory: include/linux
/*
 * linux/percpu-defs.h - basic definitions for percpu areas
 *
 * DO NOT INCLUDE DIRECTLY OUTSIDE PERCPU IMPLEMENTATION PROPER.
 *
 * This file is separate from linux/percpu.h to avoid cyclic inclusion
 * dependency from arch header files.  Only to be included from
 * asm/percpu.h.
 *
 * This file includes macros necessary to declare percpu sections and
 * variables, and definitions of percpu accessors and operations.  It
 * should provide enough percpu features to arch header files even when
 * they can only include asm/percpu.h to avoid cyclic inclusion dependency.
 */

#ifndef _LINUX_PERCPU_DEFS_H

#define _LINUX_PERCPU_DEFS_H

#ifdef CONFIG_SMP

#ifdef MODULE

#define PER_CPU_SHARED_ALIGNED_SECTION ""

#define PER_CPU_ALIGNED_SECTION ""
#else

#define PER_CPU_SHARED_ALIGNED_SECTION "..shared_aligned"

#define PER_CPU_ALIGNED_SECTION "..shared_aligned"
#endif

#define PER_CPU_FIRST_SECTION "..first"

#else


#define PER_CPU_SHARED_ALIGNED_SECTION ""

#define PER_CPU_ALIGNED_SECTION "..shared_aligned"

#define PER_CPU_FIRST_SECTION ""

#endif

/*
 * Base implementations of per-CPU variable declarations and definitions, where
 * the section in which the variable is to be placed is provided by the
 * 'sec' argument.  This may be used to affect the parameters governing the
 * variable's storage.
 *
 * NOTE!  The sections for the DECLARE and for the DEFINE must match, lest
 * linkage errors occur due the compiler generating the wrong code to access
 * that section.
 */

#define __PCPU_ATTRS(sec)						\
	__percpu __attribute__((section(PER_CPU_BASE_SECTION sec)))     \
        PER_CPU_ATTRIBUTES


#define __PCPU_DUMMY_ATTRS						\
	__attribute__((section(".discard"), unused))

/*
 * s390 and alpha modules require percpu variables to be defined as
 * weak to force the compiler to generate GOT based external
 * references for them.  This is necessary because percpu sections
 * will be located outside of the usually addressable area.
 *
 * This definition puts the following two extra restrictions when
 * defining percpu variables.
 *
 * 1. The symbol must be globally unique, even the static ones.
 * 2. Static percpu variables cannot be defined inside a function.
 *
 * Archs which need weak percpu definitions should define
 * ARCH_NEEDS_WEAK_PER_CPU in asm/percpu.h when necessary.
 *
 * To ensure that the generic code observes the above two
 * restrictions, if CONFIG_DEBUG_FORCE_WEAK_PER_CPU is set weak
 * definition is used for all cases.
 */
#if defined(ARCH_NEEDS_WEAK_PER_CPU) || defined(CONFIG_DEBUG_FORCE_WEAK_PER_CPU)
/*
 * __pcpu_scope_* dummy variable is used to enforce scope.  It
 * receives the static modifier when it's used in front of
 * DEFINE_PER_CPU() and will trigger build failure if
 * DECLARE_PER_CPU() is used for the same variable.
 *
 * __pcpu_unique_* dummy variable is used to enforce symbol uniqueness
 * such that hidden weak symbol collision, which will cause unrelated
 * variables to share the same address, can be detected during build.
 */

#define DECLARE_PER_CPU_SECTION(type, name, sec)			\
	extern __PCPU_DUMMY_ATTRS char __pcpu_scope_##name;             \
        extern __PCPU_ATTRS(sec) __typeof__(type) name


#define DEFINE_PER_CPU_SECTION(type, name, sec)				\
	__PCPU_DUMMY_ATTRS char __pcpu_scope_##name;                    \
        extern __PCPU_DUMMY_ATTRS char __pcpu_unique_##name;            \
        __PCPU_DUMMY_ATTRS char __pcpu_unique_##name;                   \
        extern __PCPU_ATTRS(sec) __typeof__(type) name;                 \
        __PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES __weak                 \
        __typeof__(type) name
#else
/*
 * Normal declaration and definition macros.
 */

#define DECLARE_PER_CPU_SECTION(type, name, sec)			\
	extern __PCPU_ATTRS(sec) __typeof__(type) name


#define DEFINE_PER_CPU_SECTION(type, name, sec)				\
	__PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES                        \
        __typeof__(type) name
#endif

/*
 * Variant on the per-CPU variable declaration/definition theme used for
 * ordinary per-CPU variables.
 */

#define DECLARE_PER_CPU(type, name)					\
	DECLARE_PER_CPU_SECTION(type, name, "")


#define DEFINE_PER_CPU(type, name)					\
	DEFINE_PER_CPU_SECTION(type, name, "")

/*
 * Declaration/definition used for per-CPU variables that must come first in
 * the set of variables.
 */

#define DECLARE_PER_CPU_FIRST(type, name)				\
	DECLARE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)


#define DEFINE_PER_CPU_FIRST(type, name)				\
	DEFINE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)

/*
 * Declaration/definition used for per-CPU variables that must be cacheline
 * aligned under SMP conditions so that, whilst a particular instance of the
 * data corresponds to a particular CPU, inefficiencies due to direct access by
 * other CPUs are reduced by preventing the data from unnecessarily spanning
 * cachelines.
 *
 * An example of this would be statistical data, where each CPU's set of data
 * is updated by that CPU alone, but the data from across all CPUs is collated
 * by a CPU processing a read from a proc file.
 */

#define DECLARE_PER_CPU_SHARED_ALIGNED(type, name)			\
	DECLARE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
        ____cacheline_aligned_in_smp


#define DEFINE_PER_CPU_SHARED_ALIGNED(type, name)			\
	DEFINE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
        ____cacheline_aligned_in_smp


#define DECLARE_PER_CPU_ALIGNED(type, name)				\
	DECLARE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION)    \
        ____cacheline_aligned


#define DEFINE_PER_CPU_ALIGNED(type, name)				\
	DEFINE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION)     \
        ____cacheline_aligned

/*
 * Declaration/definition used for per-CPU variables that must be page aligned.
 */

#define DECLARE_PER_CPU_PAGE_ALIGNED(type, name)			\
	DECLARE_PER_CPU_SECTION(type, name, "..page_aligned")           \
        __aligned(PAGE_SIZE)


#define DEFINE_PER_CPU_PAGE_ALIGNED(type, name)				\
	DEFINE_PER_CPU_SECTION(type, name, "..page_aligned")            \
        __aligned(PAGE_SIZE)

/*
 * Declaration/definition used for per-CPU variables that must be read mostly.
 */

#define DECLARE_PER_CPU_READ_MOSTLY(type, name)			\
	DECLARE_PER_CPU_SECTION(type, name, "..read_mostly")


#define DEFINE_PER_CPU_READ_MOSTLY(type, name)				\
	DEFINE_PER_CPU_SECTION(type, name, "..read_mostly")

/*
 * Intermodule exports for per-CPU variables.  sparse forgets about
 * address space across EXPORT_SYMBOL(), change EXPORT_SYMBOL() to
 * noop if __CHECKER__.
 */
#ifndef __CHECKER__

#define EXPORT_PER_CPU_SYMBOL(var) EXPORT_SYMBOL(var)

#define EXPORT_PER_CPU_SYMBOL_GPL(var) EXPORT_SYMBOL_GPL(var)
#else

#define EXPORT_PER_CPU_SYMBOL(var)

#define EXPORT_PER_CPU_SYMBOL_GPL(var)
#endif

/*
 * Accessors and operations.
 */
#ifndef __ASSEMBLY__

/*
 * __verify_pcpu_ptr() verifies @ptr is a percpu pointer without evaluating
 * @ptr and is invoked once before a percpu area is accessed by all
 * accessors and operations.  This is performed in the generic part of
 * percpu and arch overrides don't need to worry about it; however, if an
 * arch wants to implement an arch-specific percpu accessor or operation,
 * it may use __verify_pcpu_ptr() to verify the parameters.
 *
 * + 0 is required in order to convert the pointer type from a
 * potential array type to a pointer to a single item of the array.
 */

#define __verify_pcpu_ptr(ptr)						\
do {                                                                    \
        const void __percpu *__vpp_verify = (typeof((ptr) + 0))NULL;    \
        (void)__vpp_verify;                                             \
} while (0)

#ifdef CONFIG_SMP

/*
 * Add an offset to a pointer but keep the pointer as-is.  Use RELOC_HIDE()
 * to prevent the compiler from making incorrect assumptions about the
 * pointer value.  The weird cast keeps both GCC and sparse happy.
 */

#define SHIFT_PERCPU_PTR(__p, __offset)					\
	RELOC_HIDE((typeof(*(__p)) __kernel __force *)(__p), (__offset))


#define per_cpu_ptr(ptr, cpu)						\
({                                                                      \
        __verify_pcpu_ptr(ptr);                                         \
        SHIFT_PERCPU_PTR((ptr), per_cpu_offset((cpu)));                 \
})


#define raw_cpu_ptr(ptr)						\
({                                                                      \
        __verify_pcpu_ptr(ptr);                                         \
        arch_raw_cpu_ptr(ptr);                                          \
})

#ifdef CONFIG_DEBUG_PREEMPT

#define this_cpu_ptr(ptr)						\
({                                                                      \
        __verify_pcpu_ptr(ptr);                                         \
        SHIFT_PERCPU_PTR(ptr, my_cpu_offset);                           \
})
#else

#define this_cpu_ptr(ptr) raw_cpu_ptr(ptr)
#endif

#else	/* CONFIG_SMP */


#define VERIFY_PERCPU_PTR(__p)						\
({                                                                      \
        __verify_pcpu_ptr(__p);                                         \
        (typeof(*(__p)) __kernel __force *)(__p);                       \
})


#define per_cpu_ptr(ptr, cpu)	({ (void)(cpu); VERIFY_PERCPU_PTR(ptr); })

#define raw_cpu_ptr(ptr)	per_cpu_ptr(ptr, 0)

#define this_cpu_ptr(ptr)	raw_cpu_ptr(ptr)

#endif	/* CONFIG_SMP */


#define per_cpu(var, cpu)	(*per_cpu_ptr(&(var), cpu))

/*
 * Must be an lvalue. Since @var must be a simple identifier,
 * we force a syntax error here if it isn't.
 */

#define get_cpu_var(var)						\
(*({                                                                    \
        preempt_disable();                                              \
        this_cpu_ptr(&var);                                             \
}))

/*
 * The weird & is necessary because sparse considers (void)(var) to be
 * a direct dereference of percpu variable (var).
 */

#define put_cpu_var(var)						\
do {                                                                    \
        (void)&(var);                                                   \
        preempt_enable();                                               \
} while (0)


#define get_cpu_ptr(var)						\
({                                                                      \
        preempt_disable();                                              \
        this_cpu_ptr(var);                                              \
})


#define put_cpu_ptr(var)						\
do {                                                                    \
        (void)(var);                                                    \
        preempt_enable();                                               \
} while (0)

/*
 * Branching function to split up a function into a set of functions that
 * are called for different scalar sizes of the objects handled.
 */

extern void __bad_size_call_parameter(void);

#ifdef CONFIG_DEBUG_PREEMPT
extern void __this_cpu_preempt_check(const char *op);
#else

static inline void __this_cpu_preempt_check(const char *op) { }

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#endif #define __pcpu_size_call_return(stem, variable) \ ({ \ typeof(variable) pscr_ret__; \ __verify_pcpu_ptr(&(variable)); \ switch(sizeof(variable)) { \ case 1: pscr_ret__ = stem##1(variable); break; \ case 2: pscr_ret__ = stem##2(variable); break; \ case 4: pscr_ret__ = stem##4(variable); break; \ case 8: pscr_ret__ = stem##8(variable); break; \ default: \ __bad_size_call_parameter(); break; \ } \ pscr_ret__; \ }) #define __pcpu_size_call_return2(stem, variable, ...) \ ({ \ typeof(variable) pscr2_ret__; \ __verify_pcpu_ptr(&(variable)); \ switch(sizeof(variable)) { \ case 1: pscr2_ret__ = stem##1(variable, __VA_ARGS__); break; \ case 2: pscr2_ret__ = stem##2(variable, __VA_ARGS__); break; \ case 4: pscr2_ret__ = stem##4(variable, __VA_ARGS__); break; \ case 8: pscr2_ret__ = stem##8(variable, __VA_ARGS__); break; \ default: \ __bad_size_call_parameter(); break; \ } \ 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. * We enforce this on all architectures even if they don't support * a double cmpxchg instruction, since it's a cheap requirement, and it * avoids breaking the requirement for architectures with the instruction. */ #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)); \ switch(sizeof(variable)) { \ case 1: stem##1(variable, __VA_ARGS__);break; \ case 2: stem##2(variable, __VA_ARGS__);break; \ case 4: stem##4(variable, __VA_ARGS__);break; \ case 8: stem##8(variable, __VA_ARGS__);break; \ default: \ __bad_size_call_parameter();break; \ } \ } while (0) /* * this_cpu operations (C) 2008-2013 Christoph Lameter <cl@linux.com> * * Optimized manipulation for memory allocated through the per cpu * allocator or for addresses of per cpu variables. * * These operation guarantee exclusivity of access for other operations * on the *same* processor. The assumption is that per cpu data is only * accessed by a single processor instance (the current one). * * The arch code can provide optimized implementation by defining macros * for certain scalar sizes. F.e. provide this_cpu_add_2() to provide per * cpu atomic operations for 2 byte sized RMW actions. If arch code does * not provide operations for a scalar size then the fallback in the * generic code will be used. * * 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. */ /* * Operations for contexts where we do not want to do any checks for * preemptions. Unless strictly necessary, always use [__]this_cpu_*() * instead. * * If there is no other protection through preempt disable and/or disabling * interupts then one of these RMW operations can show unexpected behavior * because the execution thread was rescheduled on another processor or an * interrupt occurred and the same percpu variable was modified from the * interrupt context. */ #define raw_cpu_read(pcp) __pcpu_size_call_return(raw_cpu_read_, pcp) #define raw_cpu_write(pcp, val) __pcpu_size_call(raw_cpu_write_, pcp, val) #define raw_cpu_add(pcp, val) __pcpu_size_call(raw_cpu_add_, pcp, val) #define raw_cpu_and(pcp, val) __pcpu_size_call(raw_cpu_and_, pcp, val) #define raw_cpu_or(pcp, val) __pcpu_size_call(raw_cpu_or_, pcp, val) #define raw_cpu_add_return(pcp, val) __pcpu_size_call_return2(raw_cpu_add_return_, pcp, val) #define raw_cpu_xchg(pcp, nval) __pcpu_size_call_return2(raw_cpu_xchg_, pcp, nval) #define raw_cpu_cmpxchg(pcp, oval, nval) \ __pcpu_size_call_return2(raw_cpu_cmpxchg_, pcp, oval, nval) #define raw_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2) \ __pcpu_double_call_return_bool(raw_cpu_cmpxchg_double_, pcp1, pcp2, oval1, oval2, nval1, nval2) #define raw_cpu_sub(pcp, val) raw_cpu_add(pcp, -(val)) #define raw_cpu_inc(pcp) raw_cpu_add(pcp, 1) #define raw_cpu_dec(pcp) raw_cpu_sub(pcp, 1) #define raw_cpu_sub_return(pcp, val) raw_cpu_add_return(pcp, -(typeof(pcp))(val)) #define raw_cpu_inc_return(pcp) raw_cpu_add_return(pcp, 1) #define raw_cpu_dec_return(pcp) raw_cpu_add_return(pcp, -1) /* * Operations for contexts that are safe from preemption/interrupts. These * operations verify that preemption is disabled. */ #define __this_cpu_read(pcp) \ ({ \ __this_cpu_preempt_check("read"); \ raw_cpu_read(pcp); \ }) #define __this_cpu_write(pcp, val) \ ({ \ __this_cpu_preempt_check("write"); \ raw_cpu_write(pcp, val); \ }) #define __this_cpu_add(pcp, val) \ ({ \ __this_cpu_preempt_check("add"); \ raw_cpu_add(pcp, val); \ }) #define __this_cpu_and(pcp, val) \ ({ \ __this_cpu_preempt_check("and"); \ raw_cpu_and(pcp, val); \ }) #define __this_cpu_or(pcp, val) \ ({ \ __this_cpu_preempt_check("or"); \ raw_cpu_or(pcp, val); \ }) #define __this_cpu_add_return(pcp, val) \ ({ \ __this_cpu_preempt_check("add_return"); \ raw_cpu_add_return(pcp, val); \ }) #define __this_cpu_xchg(pcp, nval) \ ({ \ __this_cpu_preempt_check("xchg"); \ raw_cpu_xchg(pcp, nval); \ }) #define __this_cpu_cmpxchg(pcp, oval, nval) \ ({ \ __this_cpu_preempt_check("cmpxchg"); \ raw_cpu_cmpxchg(pcp, oval, nval); \ }) #define __this_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2) \ ({ __this_cpu_preempt_check("cmpxchg_double"); \ raw_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2); \ }) #define __this_cpu_sub(pcp, val) __this_cpu_add(pcp, -(typeof(pcp))(val)) #define __this_cpu_inc(pcp) __this_cpu_add(pcp, 1) #define __this_cpu_dec(pcp) __this_cpu_sub(pcp, 1) #define __this_cpu_sub_return(pcp, val) __this_cpu_add_return(pcp, -(typeof(pcp))(val)) #define __this_cpu_inc_return(pcp) __this_cpu_add_return(pcp, 1) #define __this_cpu_dec_return(pcp) __this_cpu_add_return(pcp, -1) /* * Operations with implied preemption/interrupt protection. These * operations can be used without worrying about preemption or interrupt. */ #define this_cpu_read(pcp) __pcpu_size_call_return(this_cpu_read_, pcp) #define this_cpu_write(pcp, val) __pcpu_size_call(this_cpu_write_, pcp, val) #define this_cpu_add(pcp, val) __pcpu_size_call(this_cpu_add_, pcp, val) #define this_cpu_and(pcp, val) __pcpu_size_call(this_cpu_and_, pcp, val) #define this_cpu_or(pcp, val) __pcpu_size_call(this_cpu_or_, pcp, val) #define this_cpu_add_return(pcp, val) __pcpu_size_call_return2(this_cpu_add_return_, pcp, val) #define this_cpu_xchg(pcp, nval) __pcpu_size_call_return2(this_cpu_xchg_, pcp, nval) #define this_cpu_cmpxchg(pcp, oval, nval) \ __pcpu_size_call_return2(this_cpu_cmpxchg_, pcp, oval, nval) #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) #define this_cpu_sub(pcp, val) this_cpu_add(pcp, -(typeof(pcp))(val)) #define this_cpu_inc(pcp) this_cpu_add(pcp, 1) #define this_cpu_dec(pcp) this_cpu_sub(pcp, 1) #define this_cpu_sub_return(pcp, val) this_cpu_add_return(pcp, -(typeof(pcp))(val)) #define this_cpu_inc_return(pcp) this_cpu_add_return(pcp, 1) #define this_cpu_dec_return(pcp) this_cpu_add_return(pcp, -1) #endif /* __ASSEMBLY__ */ #endif /* _LINUX_PERCPU_DEFS_H */

Overall Contributors

PersonTokensPropCommitsCommitProp
Tejun Heo78081.93%1161.11%
David Howells12312.92%15.56%
Jeremy Fitzhardinge202.10%15.56%
David Shaohua Li192.00%15.56%
Rusty Russell60.63%211.11%
Denys Vlasenko20.21%15.56%
Zhengyu He20.21%15.56%
Total952100.00%18100.00%
Directory: include/linux
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