1 #ifndef _LINUX_PERCPU_DEFS_H 2 #define _LINUX_PERCPU_DEFS_H 3 4 /* 5 * Base implementations of per-CPU variable declarations and definitions, where 6 * the section in which the variable is to be placed is provided by the 7 * 'sec' argument. This may be used to affect the parameters governing the 8 * variable's storage. 9 * 10 * NOTE! The sections for the DECLARE and for the DEFINE must match, lest 11 * linkage errors occur due the compiler generating the wrong code to access 12 * that section. 13 */ 14 #define __PCPU_ATTRS(sec) \ 15 __percpu __attribute__((section(PER_CPU_BASE_SECTION sec))) \ 16 PER_CPU_ATTRIBUTES 17 18 #define __PCPU_DUMMY_ATTRS \ 19 __attribute__((section(".discard"), unused)) 20 21 /* 22 * Macro which verifies @ptr is a percpu pointer without evaluating 23 * @ptr. This is to be used in percpu accessors to verify that the 24 * input parameter is a percpu pointer. 25 * 26 * + 0 is required in order to convert the pointer type from a 27 * potential array type to a pointer to a single item of the array. 28 */ 29 #define __verify_pcpu_ptr(ptr) do { \ 30 const void __percpu *__vpp_verify = (typeof((ptr) + 0))NULL; \ 31 (void)__vpp_verify; \ 32 } while (0) 33 34 /* 35 * s390 and alpha modules require percpu variables to be defined as 36 * weak to force the compiler to generate GOT based external 37 * references for them. This is necessary because percpu sections 38 * will be located outside of the usually addressable area. 39 * 40 * This definition puts the following two extra restrictions when 41 * defining percpu variables. 42 * 43 * 1. The symbol must be globally unique, even the static ones. 44 * 2. Static percpu variables cannot be defined inside a function. 45 * 46 * Archs which need weak percpu definitions should define 47 * ARCH_NEEDS_WEAK_PER_CPU in asm/percpu.h when necessary. 48 * 49 * To ensure that the generic code observes the above two 50 * restrictions, if CONFIG_DEBUG_FORCE_WEAK_PER_CPU is set weak 51 * definition is used for all cases. 52 */ 53 #if defined(ARCH_NEEDS_WEAK_PER_CPU) || defined(CONFIG_DEBUG_FORCE_WEAK_PER_CPU) 54 /* 55 * __pcpu_scope_* dummy variable is used to enforce scope. It 56 * receives the static modifier when it's used in front of 57 * DEFINE_PER_CPU() and will trigger build failure if 58 * DECLARE_PER_CPU() is used for the same variable. 59 * 60 * __pcpu_unique_* dummy variable is used to enforce symbol uniqueness 61 * such that hidden weak symbol collision, which will cause unrelated 62 * variables to share the same address, can be detected during build. 63 */ 64 #define DECLARE_PER_CPU_SECTION(type, name, sec) \ 65 extern __PCPU_DUMMY_ATTRS char __pcpu_scope_##name; \ 66 extern __PCPU_ATTRS(sec) __typeof__(type) name 67 68 #define DEFINE_PER_CPU_SECTION(type, name, sec) \ 69 __PCPU_DUMMY_ATTRS char __pcpu_scope_##name; \ 70 extern __PCPU_DUMMY_ATTRS char __pcpu_unique_##name; \ 71 __PCPU_DUMMY_ATTRS char __pcpu_unique_##name; \ 72 __PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES __weak \ 73 __typeof__(type) name 74 #else 75 /* 76 * Normal declaration and definition macros. 77 */ 78 #define DECLARE_PER_CPU_SECTION(type, name, sec) \ 79 extern __PCPU_ATTRS(sec) __typeof__(type) name 80 81 #define DEFINE_PER_CPU_SECTION(type, name, sec) \ 82 __PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES \ 83 __typeof__(type) name 84 #endif 85 86 /* 87 * Variant on the per-CPU variable declaration/definition theme used for 88 * ordinary per-CPU variables. 89 */ 90 #define DECLARE_PER_CPU(type, name) \ 91 DECLARE_PER_CPU_SECTION(type, name, "") 92 93 #define DEFINE_PER_CPU(type, name) \ 94 DEFINE_PER_CPU_SECTION(type, name, "") 95 96 /* 97 * Declaration/definition used for per-CPU variables that must come first in 98 * the set of variables. 99 */ 100 #define DECLARE_PER_CPU_FIRST(type, name) \ 101 DECLARE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION) 102 103 #define DEFINE_PER_CPU_FIRST(type, name) \ 104 DEFINE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION) 105 106 /* 107 * Declaration/definition used for per-CPU variables that must be cacheline 108 * aligned under SMP conditions so that, whilst a particular instance of the 109 * data corresponds to a particular CPU, inefficiencies due to direct access by 110 * other CPUs are reduced by preventing the data from unnecessarily spanning 111 * cachelines. 112 * 113 * An example of this would be statistical data, where each CPU's set of data 114 * is updated by that CPU alone, but the data from across all CPUs is collated 115 * by a CPU processing a read from a proc file. 116 */ 117 #define DECLARE_PER_CPU_SHARED_ALIGNED(type, name) \ 118 DECLARE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \ 119 ____cacheline_aligned_in_smp 120 121 #define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \ 122 DEFINE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \ 123 ____cacheline_aligned_in_smp 124 125 #define DECLARE_PER_CPU_ALIGNED(type, name) \ 126 DECLARE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION) \ 127 ____cacheline_aligned 128 129 #define DEFINE_PER_CPU_ALIGNED(type, name) \ 130 DEFINE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION) \ 131 ____cacheline_aligned 132 133 /* 134 * Declaration/definition used for per-CPU variables that must be page aligned. 135 */ 136 #define DECLARE_PER_CPU_PAGE_ALIGNED(type, name) \ 137 DECLARE_PER_CPU_SECTION(type, name, "..page_aligned") \ 138 __aligned(PAGE_SIZE) 139 140 #define DEFINE_PER_CPU_PAGE_ALIGNED(type, name) \ 141 DEFINE_PER_CPU_SECTION(type, name, "..page_aligned") \ 142 __aligned(PAGE_SIZE) 143 144 /* 145 * Declaration/definition used for per-CPU variables that must be read mostly. 146 */ 147 #define DECLARE_PER_CPU_READ_MOSTLY(type, name) \ 148 DECLARE_PER_CPU_SECTION(type, name, "..readmostly") 149 150 #define DEFINE_PER_CPU_READ_MOSTLY(type, name) \ 151 DEFINE_PER_CPU_SECTION(type, name, "..readmostly") 152 153 /* 154 * Intermodule exports for per-CPU variables. sparse forgets about 155 * address space across EXPORT_SYMBOL(), change EXPORT_SYMBOL() to 156 * noop if __CHECKER__. 157 */ 158 #ifndef __CHECKER__ 159 #define EXPORT_PER_CPU_SYMBOL(var) EXPORT_SYMBOL(var) 160 #define EXPORT_PER_CPU_SYMBOL_GPL(var) EXPORT_SYMBOL_GPL(var) 161 #else 162 #define EXPORT_PER_CPU_SYMBOL(var) 163 #define EXPORT_PER_CPU_SYMBOL_GPL(var) 164 #endif 165 166 #endif /* _LINUX_PERCPU_DEFS_H */ 167