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 #define __verify_pcpu_ptr(ptr) do { \ 27 const void __percpu *__vpp_verify = (typeof(ptr))NULL; \ 28 (void)__vpp_verify; \ 29 } while (0) 30 31 /* 32 * s390 and alpha modules require percpu variables to be defined as 33 * weak to force the compiler to generate GOT based external 34 * references for them. This is necessary because percpu sections 35 * will be located outside of the usually addressable area. 36 * 37 * This definition puts the following two extra restrictions when 38 * defining percpu variables. 39 * 40 * 1. The symbol must be globally unique, even the static ones. 41 * 2. Static percpu variables cannot be defined inside a function. 42 * 43 * Archs which need weak percpu definitions should define 44 * ARCH_NEEDS_WEAK_PER_CPU in asm/percpu.h when necessary. 45 * 46 * To ensure that the generic code observes the above two 47 * restrictions, if CONFIG_DEBUG_FORCE_WEAK_PER_CPU is set weak 48 * definition is used for all cases. 49 */ 50 #if defined(ARCH_NEEDS_WEAK_PER_CPU) || defined(CONFIG_DEBUG_FORCE_WEAK_PER_CPU) 51 /* 52 * __pcpu_scope_* dummy variable is used to enforce scope. It 53 * receives the static modifier when it's used in front of 54 * DEFINE_PER_CPU() and will trigger build failure if 55 * DECLARE_PER_CPU() is used for the same variable. 56 * 57 * __pcpu_unique_* dummy variable is used to enforce symbol uniqueness 58 * such that hidden weak symbol collision, which will cause unrelated 59 * variables to share the same address, can be detected during build. 60 */ 61 #define DECLARE_PER_CPU_SECTION(type, name, sec) \ 62 extern __PCPU_DUMMY_ATTRS char __pcpu_scope_##name; \ 63 extern __PCPU_ATTRS(sec) __typeof__(type) name 64 65 #define DEFINE_PER_CPU_SECTION(type, name, sec) \ 66 __PCPU_DUMMY_ATTRS char __pcpu_scope_##name; \ 67 extern __PCPU_DUMMY_ATTRS char __pcpu_unique_##name; \ 68 __PCPU_DUMMY_ATTRS char __pcpu_unique_##name; \ 69 __PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES __weak \ 70 __typeof__(type) name 71 #else 72 /* 73 * Normal declaration and definition macros. 74 */ 75 #define DECLARE_PER_CPU_SECTION(type, name, sec) \ 76 extern __PCPU_ATTRS(sec) __typeof__(type) name 77 78 #define DEFINE_PER_CPU_SECTION(type, name, sec) \ 79 __PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES \ 80 __typeof__(type) name 81 #endif 82 83 /* 84 * Variant on the per-CPU variable declaration/definition theme used for 85 * ordinary per-CPU variables. 86 */ 87 #define DECLARE_PER_CPU(type, name) \ 88 DECLARE_PER_CPU_SECTION(type, name, "") 89 90 #define DEFINE_PER_CPU(type, name) \ 91 DEFINE_PER_CPU_SECTION(type, name, "") 92 93 /* 94 * Declaration/definition used for per-CPU variables that must come first in 95 * the set of variables. 96 */ 97 #define DECLARE_PER_CPU_FIRST(type, name) \ 98 DECLARE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION) 99 100 #define DEFINE_PER_CPU_FIRST(type, name) \ 101 DEFINE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION) 102 103 /* 104 * Declaration/definition used for per-CPU variables that must be cacheline 105 * aligned under SMP conditions so that, whilst a particular instance of the 106 * data corresponds to a particular CPU, inefficiencies due to direct access by 107 * other CPUs are reduced by preventing the data from unnecessarily spanning 108 * cachelines. 109 * 110 * An example of this would be statistical data, where each CPU's set of data 111 * is updated by that CPU alone, but the data from across all CPUs is collated 112 * by a CPU processing a read from a proc file. 113 */ 114 #define DECLARE_PER_CPU_SHARED_ALIGNED(type, name) \ 115 DECLARE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \ 116 ____cacheline_aligned_in_smp 117 118 #define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \ 119 DEFINE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \ 120 ____cacheline_aligned_in_smp 121 122 #define DECLARE_PER_CPU_ALIGNED(type, name) \ 123 DECLARE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION) \ 124 ____cacheline_aligned 125 126 #define DEFINE_PER_CPU_ALIGNED(type, name) \ 127 DEFINE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION) \ 128 ____cacheline_aligned 129 130 /* 131 * Declaration/definition used for per-CPU variables that must be page aligned. 132 */ 133 #define DECLARE_PER_CPU_PAGE_ALIGNED(type, name) \ 134 DECLARE_PER_CPU_SECTION(type, name, "..page_aligned") \ 135 __aligned(PAGE_SIZE) 136 137 #define DEFINE_PER_CPU_PAGE_ALIGNED(type, name) \ 138 DEFINE_PER_CPU_SECTION(type, name, "..page_aligned") \ 139 __aligned(PAGE_SIZE) 140 141 /* 142 * Declaration/definition used for per-CPU variables that must be read mostly. 143 */ 144 #define DECLARE_PER_CPU_READ_MOSTLY(type, name) \ 145 DECLARE_PER_CPU_SECTION(type, name, "..readmostly") 146 147 #define DEFINE_PER_CPU_READ_MOSTLY(type, name) \ 148 DEFINE_PER_CPU_SECTION(type, name, "..readmostly") 149 150 /* 151 * Intermodule exports for per-CPU variables. sparse forgets about 152 * address space across EXPORT_SYMBOL(), change EXPORT_SYMBOL() to 153 * noop if __CHECKER__. 154 */ 155 #ifndef __CHECKER__ 156 #define EXPORT_PER_CPU_SYMBOL(var) EXPORT_SYMBOL(var) 157 #define EXPORT_PER_CPU_SYMBOL_GPL(var) EXPORT_SYMBOL_GPL(var) 158 #else 159 #define EXPORT_PER_CPU_SYMBOL(var) 160 #define EXPORT_PER_CPU_SYMBOL_GPL(var) 161 #endif 162 163 #endif /* _LINUX_PERCPU_DEFS_H */ 164