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Diffstat (limited to 'include/linux/percpu-defs.h')
| -rw-r--r-- | include/linux/percpu-defs.h | 516 |
1 files changed, 516 insertions, 0 deletions
diff --git a/include/linux/percpu-defs.h b/include/linux/percpu-defs.h new file mode 100644 index 000000000..57f3a1c55 --- /dev/null +++ b/include/linux/percpu-defs.h @@ -0,0 +1,516 @@ +/* + * 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) { } +#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 */ |