1/* 2 * linux/percpu-defs.h - basic definitions for percpu areas 3 * 4 * DO NOT INCLUDE DIRECTLY OUTSIDE PERCPU IMPLEMENTATION PROPER. 5 * 6 * This file is separate from linux/percpu.h to avoid cyclic inclusion 7 * dependency from arch header files. Only to be included from 8 * asm/percpu.h. 9 * 10 * This file includes macros necessary to declare percpu sections and 11 * variables, and definitions of percpu accessors and operations. It 12 * should provide enough percpu features to arch header files even when 13 * they can only include asm/percpu.h to avoid cyclic inclusion dependency. 14 */ 15 16#ifndef _LINUX_PERCPU_DEFS_H 17#define _LINUX_PERCPU_DEFS_H 18 19#ifdef CONFIG_SMP 20 21#ifdef MODULE 22#define PER_CPU_SHARED_ALIGNED_SECTION "" 23#define PER_CPU_ALIGNED_SECTION "" 24#else 25#define PER_CPU_SHARED_ALIGNED_SECTION "..shared_aligned" 26#define PER_CPU_ALIGNED_SECTION "..shared_aligned" 27#endif 28#define PER_CPU_FIRST_SECTION "..first" 29 30#else 31 32#define PER_CPU_SHARED_ALIGNED_SECTION "" 33#define PER_CPU_ALIGNED_SECTION "..shared_aligned" 34#define PER_CPU_FIRST_SECTION "" 35 36#endif 37 38/* 39 * Base implementations of per-CPU variable declarations and definitions, where 40 * the section in which the variable is to be placed is provided by the 41 * 'sec' argument. This may be used to affect the parameters governing the 42 * variable's storage. 43 * 44 * NOTE! The sections for the DECLARE and for the DEFINE must match, lest 45 * linkage errors occur due the compiler generating the wrong code to access 46 * that section. 47 */ 48#define __PCPU_ATTRS(sec) \ 49 __percpu __attribute__((section(PER_CPU_BASE_SECTION sec))) \ 50 PER_CPU_ATTRIBUTES 51 52#define __PCPU_DUMMY_ATTRS \ 53 __attribute__((section(".discard"), unused)) 54 55/* 56 * s390 and alpha modules require percpu variables to be defined as 57 * weak to force the compiler to generate GOT based external 58 * references for them. This is necessary because percpu sections 59 * will be located outside of the usually addressable area. 60 * 61 * This definition puts the following two extra restrictions when 62 * defining percpu variables. 63 * 64 * 1. The symbol must be globally unique, even the static ones. 65 * 2. Static percpu variables cannot be defined inside a function. 66 * 67 * Archs which need weak percpu definitions should define 68 * ARCH_NEEDS_WEAK_PER_CPU in asm/percpu.h when necessary. 69 * 70 * To ensure that the generic code observes the above two 71 * restrictions, if CONFIG_DEBUG_FORCE_WEAK_PER_CPU is set weak 72 * definition is used for all cases. 73 */ 74#if defined(ARCH_NEEDS_WEAK_PER_CPU) || defined(CONFIG_DEBUG_FORCE_WEAK_PER_CPU) 75/* 76 * __pcpu_scope_* dummy variable is used to enforce scope. It 77 * receives the static modifier when it's used in front of 78 * DEFINE_PER_CPU() and will trigger build failure if 79 * DECLARE_PER_CPU() is used for the same variable. 80 * 81 * __pcpu_unique_* dummy variable is used to enforce symbol uniqueness 82 * such that hidden weak symbol collision, which will cause unrelated 83 * variables to share the same address, can be detected during build. 84 */ 85#define DECLARE_PER_CPU_SECTION(type, name, sec) \ 86 extern __PCPU_DUMMY_ATTRS char __pcpu_scope_##name; \ 87 extern __PCPU_ATTRS(sec) __typeof__(type) name 88 89#define DEFINE_PER_CPU_SECTION(type, name, sec) \ 90 __PCPU_DUMMY_ATTRS char __pcpu_scope_##name; \ 91 extern __PCPU_DUMMY_ATTRS char __pcpu_unique_##name; \ 92 __PCPU_DUMMY_ATTRS char __pcpu_unique_##name; \ 93 extern __PCPU_ATTRS(sec) __typeof__(type) name; \ 94 __PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES __weak \ 95 __typeof__(type) name 96#else 97/* 98 * Normal declaration and definition macros. 99 */ 100#define DECLARE_PER_CPU_SECTION(type, name, sec) \ 101 extern __PCPU_ATTRS(sec) __typeof__(type) name 102 103#define DEFINE_PER_CPU_SECTION(type, name, sec) \ 104 __PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES \ 105 __typeof__(type) name 106#endif 107 108/* 109 * Variant on the per-CPU variable declaration/definition theme used for 110 * ordinary per-CPU variables. 111 */ 112#define DECLARE_PER_CPU(type, name) \ 113 DECLARE_PER_CPU_SECTION(type, name, "") 114 115#define DEFINE_PER_CPU(type, name) \ 116 DEFINE_PER_CPU_SECTION(type, name, "") 117 118/* 119 * Declaration/definition used for per-CPU variables that must come first in 120 * the set of variables. 121 */ 122#define DECLARE_PER_CPU_FIRST(type, name) \ 123 DECLARE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION) 124 125#define DEFINE_PER_CPU_FIRST(type, name) \ 126 DEFINE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION) 127 128/* 129 * Declaration/definition used for per-CPU variables that must be cacheline 130 * aligned under SMP conditions so that, whilst a particular instance of the 131 * data corresponds to a particular CPU, inefficiencies due to direct access by 132 * other CPUs are reduced by preventing the data from unnecessarily spanning 133 * cachelines. 134 * 135 * An example of this would be statistical data, where each CPU's set of data 136 * is updated by that CPU alone, but the data from across all CPUs is collated 137 * by a CPU processing a read from a proc file. 138 */ 139#define DECLARE_PER_CPU_SHARED_ALIGNED(type, name) \ 140 DECLARE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \ 141 ____cacheline_aligned_in_smp 142 143#define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \ 144 DEFINE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \ 145 ____cacheline_aligned_in_smp 146 147#define DECLARE_PER_CPU_ALIGNED(type, name) \ 148 DECLARE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION) \ 149 ____cacheline_aligned 150 151#define DEFINE_PER_CPU_ALIGNED(type, name) \ 152 DEFINE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION) \ 153 ____cacheline_aligned 154 155/* 156 * Declaration/definition used for per-CPU variables that must be page aligned. 157 */ 158#define DECLARE_PER_CPU_PAGE_ALIGNED(type, name) \ 159 DECLARE_PER_CPU_SECTION(type, name, "..page_aligned") \ 160 __aligned(PAGE_SIZE) 161 162#define DEFINE_PER_CPU_PAGE_ALIGNED(type, name) \ 163 DEFINE_PER_CPU_SECTION(type, name, "..page_aligned") \ 164 __aligned(PAGE_SIZE) 165 166/* 167 * Declaration/definition used for per-CPU variables that must be read mostly. 168 */ 169#define DECLARE_PER_CPU_READ_MOSTLY(type, name) \ 170 DECLARE_PER_CPU_SECTION(type, name, "..read_mostly") 171 172#define DEFINE_PER_CPU_READ_MOSTLY(type, name) \ 173 DEFINE_PER_CPU_SECTION(type, name, "..read_mostly") 174 175/* 176 * Intermodule exports for per-CPU variables. sparse forgets about 177 * address space across EXPORT_SYMBOL(), change EXPORT_SYMBOL() to 178 * noop if __CHECKER__. 179 */ 180#ifndef __CHECKER__ 181#define EXPORT_PER_CPU_SYMBOL(var) EXPORT_SYMBOL(var) 182#define EXPORT_PER_CPU_SYMBOL_GPL(var) EXPORT_SYMBOL_GPL(var) 183#else 184#define EXPORT_PER_CPU_SYMBOL(var) 185#define EXPORT_PER_CPU_SYMBOL_GPL(var) 186#endif 187 188/* 189 * Accessors and operations. 190 */ 191#ifndef __ASSEMBLY__ 192 193/* 194 * __verify_pcpu_ptr() verifies @ptr is a percpu pointer without evaluating 195 * @ptr and is invoked once before a percpu area is accessed by all 196 * accessors and operations. This is performed in the generic part of 197 * percpu and arch overrides don't need to worry about it; however, if an 198 * arch wants to implement an arch-specific percpu accessor or operation, 199 * it may use __verify_pcpu_ptr() to verify the parameters. 200 * 201 * + 0 is required in order to convert the pointer type from a 202 * potential array type to a pointer to a single item of the array. 203 */ 204#define __verify_pcpu_ptr(ptr) \ 205do { \ 206 const void __percpu *__vpp_verify = (typeof((ptr) + 0))NULL; \ 207 (void)__vpp_verify; \ 208} while (0) 209 210#ifdef CONFIG_SMP 211 212/* 213 * Add an offset to a pointer but keep the pointer as-is. Use RELOC_HIDE() 214 * to prevent the compiler from making incorrect assumptions about the 215 * pointer value. The weird cast keeps both GCC and sparse happy. 216 */ 217#define SHIFT_PERCPU_PTR(__p, __offset) \ 218 RELOC_HIDE((typeof(*(__p)) __kernel __force *)(__p), (__offset)) 219 220#define per_cpu_ptr(ptr, cpu) \ 221({ \ 222 __verify_pcpu_ptr(ptr); \ 223 SHIFT_PERCPU_PTR((ptr), per_cpu_offset((cpu))); \ 224}) 225 226#define raw_cpu_ptr(ptr) \ 227({ \ 228 __verify_pcpu_ptr(ptr); \ 229 arch_raw_cpu_ptr(ptr); \ 230}) 231 232#ifdef CONFIG_DEBUG_PREEMPT 233#define this_cpu_ptr(ptr) \ 234({ \ 235 __verify_pcpu_ptr(ptr); \ 236 SHIFT_PERCPU_PTR(ptr, my_cpu_offset); \ 237}) 238#else 239#define this_cpu_ptr(ptr) raw_cpu_ptr(ptr) 240#endif 241 242#else /* CONFIG_SMP */ 243 244#define VERIFY_PERCPU_PTR(__p) \ 245({ \ 246 __verify_pcpu_ptr(__p); \ 247 (typeof(*(__p)) __kernel __force *)(__p); \ 248}) 249 250#define per_cpu_ptr(ptr, cpu) ({ (void)(cpu); VERIFY_PERCPU_PTR(ptr); }) 251#define raw_cpu_ptr(ptr) per_cpu_ptr(ptr, 0) 252#define this_cpu_ptr(ptr) raw_cpu_ptr(ptr) 253 254#endif /* CONFIG_SMP */ 255 256#define per_cpu(var, cpu) (*per_cpu_ptr(&(var), cpu)) 257 258/* 259 * Must be an lvalue. Since @var must be a simple identifier, 260 * we force a syntax error here if it isn't. 261 */ 262#define get_cpu_var(var) \ 263(*({ \ 264 preempt_disable(); \ 265 this_cpu_ptr(&var); \ 266})) 267 268/* 269 * The weird & is necessary because sparse considers (void)(var) to be 270 * a direct dereference of percpu variable (var). 271 */ 272#define put_cpu_var(var) \ 273do { \ 274 (void)&(var); \ 275 preempt_enable(); \ 276} while (0) 277 278#define get_cpu_ptr(var) \ 279({ \ 280 preempt_disable(); \ 281 this_cpu_ptr(var); \ 282}) 283 284#define put_cpu_ptr(var) \ 285do { \ 286 (void)(var); \ 287 preempt_enable(); \ 288} while (0) 289 290/* 291 * Branching function to split up a function into a set of functions that 292 * are called for different scalar sizes of the objects handled. 293 */ 294 295extern void __bad_size_call_parameter(void); 296 297#ifdef CONFIG_DEBUG_PREEMPT 298extern void __this_cpu_preempt_check(const char *op); 299#else 300static inline void __this_cpu_preempt_check(const char *op) { } 301#endif 302 303#define __pcpu_size_call_return(stem, variable) \ 304({ \ 305 typeof(variable) pscr_ret__; \ 306 __verify_pcpu_ptr(&(variable)); \ 307 switch(sizeof(variable)) { \ 308 case 1: pscr_ret__ = stem##1(variable); break; \ 309 case 2: pscr_ret__ = stem##2(variable); break; \ 310 case 4: pscr_ret__ = stem##4(variable); break; \ 311 case 8: pscr_ret__ = stem##8(variable); break; \ 312 default: \ 313 __bad_size_call_parameter(); break; \ 314 } \ 315 pscr_ret__; \ 316}) 317 318#define __pcpu_size_call_return2(stem, variable, ...) \ 319({ \ 320 typeof(variable) pscr2_ret__; \ 321 __verify_pcpu_ptr(&(variable)); \ 322 switch(sizeof(variable)) { \ 323 case 1: pscr2_ret__ = stem##1(variable, __VA_ARGS__); break; \ 324 case 2: pscr2_ret__ = stem##2(variable, __VA_ARGS__); break; \ 325 case 4: pscr2_ret__ = stem##4(variable, __VA_ARGS__); break; \ 326 case 8: pscr2_ret__ = stem##8(variable, __VA_ARGS__); break; \ 327 default: \ 328 __bad_size_call_parameter(); break; \ 329 } \ 330 pscr2_ret__; \ 331}) 332 333/* 334 * Special handling for cmpxchg_double. cmpxchg_double is passed two 335 * percpu variables. The first has to be aligned to a double word 336 * boundary and the second has to follow directly thereafter. 337 * We enforce this on all architectures even if they don't support 338 * a double cmpxchg instruction, since it's a cheap requirement, and it 339 * avoids breaking the requirement for architectures with the instruction. 340 */ 341#define __pcpu_double_call_return_bool(stem, pcp1, pcp2, ...) \ 342({ \ 343 bool pdcrb_ret__; \ 344 __verify_pcpu_ptr(&(pcp1)); \ 345 BUILD_BUG_ON(sizeof(pcp1) != sizeof(pcp2)); \ 346 VM_BUG_ON((unsigned long)(&(pcp1)) % (2 * sizeof(pcp1))); \ 347 VM_BUG_ON((unsigned long)(&(pcp2)) != \ 348 (unsigned long)(&(pcp1)) + sizeof(pcp1)); \ 349 switch(sizeof(pcp1)) { \ 350 case 1: pdcrb_ret__ = stem##1(pcp1, pcp2, __VA_ARGS__); break; \ 351 case 2: pdcrb_ret__ = stem##2(pcp1, pcp2, __VA_ARGS__); break; \ 352 case 4: pdcrb_ret__ = stem##4(pcp1, pcp2, __VA_ARGS__); break; \ 353 case 8: pdcrb_ret__ = stem##8(pcp1, pcp2, __VA_ARGS__); break; \ 354 default: \ 355 __bad_size_call_parameter(); break; \ 356 } \ 357 pdcrb_ret__; \ 358}) 359 360#define __pcpu_size_call(stem, variable, ...) \ 361do { \ 362 __verify_pcpu_ptr(&(variable)); \ 363 switch(sizeof(variable)) { \ 364 case 1: stem##1(variable, __VA_ARGS__);break; \ 365 case 2: stem##2(variable, __VA_ARGS__);break; \ 366 case 4: stem##4(variable, __VA_ARGS__);break; \ 367 case 8: stem##8(variable, __VA_ARGS__);break; \ 368 default: \ 369 __bad_size_call_parameter();break; \ 370 } \ 371} while (0) 372 373/* 374 * this_cpu operations (C) 2008-2013 Christoph Lameter <cl@linux.com> 375 * 376 * Optimized manipulation for memory allocated through the per cpu 377 * allocator or for addresses of per cpu variables. 378 * 379 * These operation guarantee exclusivity of access for other operations 380 * on the *same* processor. The assumption is that per cpu data is only 381 * accessed by a single processor instance (the current one). 382 * 383 * The arch code can provide optimized implementation by defining macros 384 * for certain scalar sizes. F.e. provide this_cpu_add_2() to provide per 385 * cpu atomic operations for 2 byte sized RMW actions. If arch code does 386 * not provide operations for a scalar size then the fallback in the 387 * generic code will be used. 388 * 389 * cmpxchg_double replaces two adjacent scalars at once. The first two 390 * parameters are per cpu variables which have to be of the same size. A 391 * truth value is returned to indicate success or failure (since a double 392 * register result is difficult to handle). There is very limited hardware 393 * support for these operations, so only certain sizes may work. 394 */ 395 396/* 397 * Operations for contexts where we do not want to do any checks for 398 * preemptions. Unless strictly necessary, always use [__]this_cpu_*() 399 * instead. 400 * 401 * If there is no other protection through preempt disable and/or disabling 402 * interupts then one of these RMW operations can show unexpected behavior 403 * because the execution thread was rescheduled on another processor or an 404 * interrupt occurred and the same percpu variable was modified from the 405 * interrupt context. 406 */ 407#define raw_cpu_read(pcp) __pcpu_size_call_return(raw_cpu_read_, pcp) 408#define raw_cpu_write(pcp, val) __pcpu_size_call(raw_cpu_write_, pcp, val) 409#define raw_cpu_add(pcp, val) __pcpu_size_call(raw_cpu_add_, pcp, val) 410#define raw_cpu_and(pcp, val) __pcpu_size_call(raw_cpu_and_, pcp, val) 411#define raw_cpu_or(pcp, val) __pcpu_size_call(raw_cpu_or_, pcp, val) 412#define raw_cpu_add_return(pcp, val) __pcpu_size_call_return2(raw_cpu_add_return_, pcp, val) 413#define raw_cpu_xchg(pcp, nval) __pcpu_size_call_return2(raw_cpu_xchg_, pcp, nval) 414#define raw_cpu_cmpxchg(pcp, oval, nval) \ 415 __pcpu_size_call_return2(raw_cpu_cmpxchg_, pcp, oval, nval) 416#define raw_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2) \ 417 __pcpu_double_call_return_bool(raw_cpu_cmpxchg_double_, pcp1, pcp2, oval1, oval2, nval1, nval2) 418 419#define raw_cpu_sub(pcp, val) raw_cpu_add(pcp, -(val)) 420#define raw_cpu_inc(pcp) raw_cpu_add(pcp, 1) 421#define raw_cpu_dec(pcp) raw_cpu_sub(pcp, 1) 422#define raw_cpu_sub_return(pcp, val) raw_cpu_add_return(pcp, -(typeof(pcp))(val)) 423#define raw_cpu_inc_return(pcp) raw_cpu_add_return(pcp, 1) 424#define raw_cpu_dec_return(pcp) raw_cpu_add_return(pcp, -1) 425 426/* 427 * Operations for contexts that are safe from preemption/interrupts. These 428 * operations verify that preemption is disabled. 429 */ 430#define __this_cpu_read(pcp) \ 431({ \ 432 __this_cpu_preempt_check("read"); \ 433 raw_cpu_read(pcp); \ 434}) 435 436#define __this_cpu_write(pcp, val) \ 437({ \ 438 __this_cpu_preempt_check("write"); \ 439 raw_cpu_write(pcp, val); \ 440}) 441 442#define __this_cpu_add(pcp, val) \ 443({ \ 444 __this_cpu_preempt_check("add"); \ 445 raw_cpu_add(pcp, val); \ 446}) 447 448#define __this_cpu_and(pcp, val) \ 449({ \ 450 __this_cpu_preempt_check("and"); \ 451 raw_cpu_and(pcp, val); \ 452}) 453 454#define __this_cpu_or(pcp, val) \ 455({ \ 456 __this_cpu_preempt_check("or"); \ 457 raw_cpu_or(pcp, val); \ 458}) 459 460#define __this_cpu_add_return(pcp, val) \ 461({ \ 462 __this_cpu_preempt_check("add_return"); \ 463 raw_cpu_add_return(pcp, val); \ 464}) 465 466#define __this_cpu_xchg(pcp, nval) \ 467({ \ 468 __this_cpu_preempt_check("xchg"); \ 469 raw_cpu_xchg(pcp, nval); \ 470}) 471 472#define __this_cpu_cmpxchg(pcp, oval, nval) \ 473({ \ 474 __this_cpu_preempt_check("cmpxchg"); \ 475 raw_cpu_cmpxchg(pcp, oval, nval); \ 476}) 477 478#define __this_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2) \ 479({ __this_cpu_preempt_check("cmpxchg_double"); \ 480 raw_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2); \ 481}) 482 483#define __this_cpu_sub(pcp, val) __this_cpu_add(pcp, -(typeof(pcp))(val)) 484#define __this_cpu_inc(pcp) __this_cpu_add(pcp, 1) 485#define __this_cpu_dec(pcp) __this_cpu_sub(pcp, 1) 486#define __this_cpu_sub_return(pcp, val) __this_cpu_add_return(pcp, -(typeof(pcp))(val)) 487#define __this_cpu_inc_return(pcp) __this_cpu_add_return(pcp, 1) 488#define __this_cpu_dec_return(pcp) __this_cpu_add_return(pcp, -1) 489 490/* 491 * Operations with implied preemption protection. These operations can be 492 * used without worrying about preemption. Note that interrupts may still 493 * occur while an operation is in progress and if the interrupt modifies 494 * the variable too then RMW actions may not be reliable. 495 */ 496#define this_cpu_read(pcp) __pcpu_size_call_return(this_cpu_read_, pcp) 497#define this_cpu_write(pcp, val) __pcpu_size_call(this_cpu_write_, pcp, val) 498#define this_cpu_add(pcp, val) __pcpu_size_call(this_cpu_add_, pcp, val) 499#define this_cpu_and(pcp, val) __pcpu_size_call(this_cpu_and_, pcp, val) 500#define this_cpu_or(pcp, val) __pcpu_size_call(this_cpu_or_, pcp, val) 501#define this_cpu_add_return(pcp, val) __pcpu_size_call_return2(this_cpu_add_return_, pcp, val) 502#define this_cpu_xchg(pcp, nval) __pcpu_size_call_return2(this_cpu_xchg_, pcp, nval) 503#define this_cpu_cmpxchg(pcp, oval, nval) \ 504 __pcpu_size_call_return2(this_cpu_cmpxchg_, pcp, oval, nval) 505#define this_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2) \ 506 __pcpu_double_call_return_bool(this_cpu_cmpxchg_double_, pcp1, pcp2, oval1, oval2, nval1, nval2) 507 508#define this_cpu_sub(pcp, val) this_cpu_add(pcp, -(typeof(pcp))(val)) 509#define this_cpu_inc(pcp) this_cpu_add(pcp, 1) 510#define this_cpu_dec(pcp) this_cpu_sub(pcp, 1) 511#define this_cpu_sub_return(pcp, val) this_cpu_add_return(pcp, -(typeof(pcp))(val)) 512#define this_cpu_inc_return(pcp) this_cpu_add_return(pcp, 1) 513#define this_cpu_dec_return(pcp) this_cpu_add_return(pcp, -1) 514 515#endif /* __ASSEMBLY__ */ 516#endif /* _LINUX_PERCPU_DEFS_H */ 517