Release 4.7 include/linux/percpu-defs.h
/*
* 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 */
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