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linux-next/include/linux/percpu-defs.h
Linus Torvalds f2a84170ed Merge branch 'for-3.17' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu 
Pull percpu updates from Tejun Heo:

 - Major reorganization of percpu header files which I think makes
   things a lot more readable and logical than before.

 - percpu-refcount is updated so that it requires explicit destruction
   and can be reinitialized if necessary.  This was pulled into the
   block tree to replace the custom percpu refcnting implemented in
   blk-mq.

 - In the process, percpu and percpu-refcount got cleaned up a bit

* 'for-3.17' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu: (21 commits)
  percpu-refcount: implement percpu_ref_reinit() and percpu_ref_is_zero()
  percpu-refcount: require percpu_ref to be exited explicitly
  percpu-refcount: use unsigned long for pcpu_count pointer
  percpu-refcount: add helpers for ->percpu_count accesses
  percpu-refcount: one bit is enough for REF_STATUS
  percpu-refcount, aio: use percpu_ref_cancel_init() in ioctx_alloc()
  workqueue: stronger test in process_one_work()
  workqueue: clear POOL_DISASSOCIATED in rebind_workers()
  percpu: Use ALIGN macro instead of hand coding alignment calculation
  percpu: invoke __verify_pcpu_ptr() from the generic part of accessors and operations
  percpu: preffity percpu header files
  percpu: use raw_cpu_*() to define __this_cpu_*()
  percpu: reorder macros in percpu header files
  percpu: move {raw|this}_cpu_*() definitions to include/linux/percpu-defs.h
  percpu: move generic {raw|this}_cpu_*_N() definitions to include/asm-generic/percpu.h
  percpu: only allow sized arch overrides for {raw|this}_cpu_*() ops
  percpu: reorganize include/linux/percpu-defs.h
  percpu: move accessors from include/linux/percpu.h to percpu-defs.h
  percpu: include/asm-generic/percpu.h should contain only arch-overridable parts
  percpu: introduce arch_raw_cpu_ptr()
  ...
2014-08-04 10:09:27 -07:00

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/*
* 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))
#define __raw_get_cpu_var(var) (*raw_cpu_ptr(&(var)))
#define __get_cpu_var(var) (*this_cpu_ptr(&(var)))
/* keep until we have removed all uses of __this_cpu_ptr */
#define __this_cpu_ptr(ptr) raw_cpu_ptr(ptr)
/*
* 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) { }
#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 protection. These operations can be
* used without worrying about preemption. Note that interrupts may still
* occur while an operation is in progress and if the interrupt modifies
* the variable too then RMW actions may not be reliable.
*/
#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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