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, "..readmostly") 171 172 #define DEFINE_PER_CPU_READ_MOSTLY(type, name) \ 173 DEFINE_PER_CPU_SECTION(type, name, "..readmostly") 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) \ 205 do { \ 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 #define __raw_get_cpu_var(var) (*raw_cpu_ptr(&(var))) 258 #define __get_cpu_var(var) (*this_cpu_ptr(&(var))) 259 260 /* keep until we have removed all uses of __this_cpu_ptr */ 261 #define __this_cpu_ptr(ptr) raw_cpu_ptr(ptr) 262 263 /* 264 * Must be an lvalue. Since @var must be a simple identifier, 265 * we force a syntax error here if it isn't. 266 */ 267 #define get_cpu_var(var) \ 268 (*({ \ 269 preempt_disable(); \ 270 this_cpu_ptr(&var); \ 271 })) 272 273 /* 274 * The weird & is necessary because sparse considers (void)(var) to be 275 * a direct dereference of percpu variable (var). 276 */ 277 #define put_cpu_var(var) \ 278 do { \ 279 (void)&(var); \ 280 preempt_enable(); \ 281 } while (0) 282 283 #define get_cpu_ptr(var) \ 284 ({ \ 285 preempt_disable(); \ 286 this_cpu_ptr(var); \ 287 }) 288 289 #define put_cpu_ptr(var) \ 290 do { \ 291 (void)(var); \ 292 preempt_enable(); \ 293 } while (0) 294 295 /* 296 * Branching function to split up a function into a set of functions that 297 * are called for different scalar sizes of the objects handled. 298 */ 299 300 extern void __bad_size_call_parameter(void); 301 302 #ifdef CONFIG_DEBUG_PREEMPT 303 extern void __this_cpu_preempt_check(const char *op); 304 #else 305 static inline void __this_cpu_preempt_check(const char *op) { } 306 #endif 307 308 #define __pcpu_size_call_return(stem, variable) \ 309 ({ \ 310 typeof(variable) pscr_ret__; \ 311 __verify_pcpu_ptr(&(variable)); \ 312 switch(sizeof(variable)) { \ 313 case 1: pscr_ret__ = stem##1(variable); break; \ 314 case 2: pscr_ret__ = stem##2(variable); break; \ 315 case 4: pscr_ret__ = stem##4(variable); break; \ 316 case 8: pscr_ret__ = stem##8(variable); break; \ 317 default: \ 318 __bad_size_call_parameter(); break; \ 319 } \ 320 pscr_ret__; \ 321 }) 322 323 #define __pcpu_size_call_return2(stem, variable, ...) \ 324 ({ \ 325 typeof(variable) pscr2_ret__; \ 326 __verify_pcpu_ptr(&(variable)); \ 327 switch(sizeof(variable)) { \ 328 case 1: pscr2_ret__ = stem##1(variable, __VA_ARGS__); break; \ 329 case 2: pscr2_ret__ = stem##2(variable, __VA_ARGS__); break; \ 330 case 4: pscr2_ret__ = stem##4(variable, __VA_ARGS__); break; \ 331 case 8: pscr2_ret__ = stem##8(variable, __VA_ARGS__); break; \ 332 default: \ 333 __bad_size_call_parameter(); break; \ 334 } \ 335 pscr2_ret__; \ 336 }) 337 338 /* 339 * Special handling for cmpxchg_double. cmpxchg_double is passed two 340 * percpu variables. The first has to be aligned to a double word 341 * boundary and the second has to follow directly thereafter. 342 * We enforce this on all architectures even if they don't support 343 * a double cmpxchg instruction, since it's a cheap requirement, and it 344 * avoids breaking the requirement for architectures with the instruction. 345 */ 346 #define __pcpu_double_call_return_bool(stem, pcp1, pcp2, ...) \ 347 ({ \ 348 bool pdcrb_ret__; \ 349 __verify_pcpu_ptr(&(pcp1)); \ 350 BUILD_BUG_ON(sizeof(pcp1) != sizeof(pcp2)); \ 351 VM_BUG_ON((unsigned long)(&(pcp1)) % (2 * sizeof(pcp1))); \ 352 VM_BUG_ON((unsigned long)(&(pcp2)) != \ 353 (unsigned long)(&(pcp1)) + sizeof(pcp1)); \ 354 switch(sizeof(pcp1)) { \ 355 case 1: pdcrb_ret__ = stem##1(pcp1, pcp2, __VA_ARGS__); break; \ 356 case 2: pdcrb_ret__ = stem##2(pcp1, pcp2, __VA_ARGS__); break; \ 357 case 4: pdcrb_ret__ = stem##4(pcp1, pcp2, __VA_ARGS__); break; \ 358 case 8: pdcrb_ret__ = stem##8(pcp1, pcp2, __VA_ARGS__); break; \ 359 default: \ 360 __bad_size_call_parameter(); break; \ 361 } \ 362 pdcrb_ret__; \ 363 }) 364 365 #define __pcpu_size_call(stem, variable, ...) \ 366 do { \ 367 __verify_pcpu_ptr(&(variable)); \ 368 switch(sizeof(variable)) { \ 369 case 1: stem##1(variable, __VA_ARGS__);break; \ 370 case 2: stem##2(variable, __VA_ARGS__);break; \ 371 case 4: stem##4(variable, __VA_ARGS__);break; \ 372 case 8: stem##8(variable, __VA_ARGS__);break; \ 373 default: \ 374 __bad_size_call_parameter();break; \ 375 } \ 376 } while (0) 377 378 /* 379 * this_cpu operations (C) 2008-2013 Christoph Lameter <[email protected]> 380 * 381 * Optimized manipulation for memory allocated through the per cpu 382 * allocator or for addresses of per cpu variables. 383 * 384 * These operation guarantee exclusivity of access for other operations 385 * on the *same* processor. The assumption is that per cpu data is only 386 * accessed by a single processor instance (the current one). 387 * 388 * The arch code can provide optimized implementation by defining macros 389 * for certain scalar sizes. F.e. provide this_cpu_add_2() to provide per 390 * cpu atomic operations for 2 byte sized RMW actions. If arch code does 391 * not provide operations for a scalar size then the fallback in the 392 * generic code will be used. 393 * 394 * cmpxchg_double replaces two adjacent scalars at once. The first two 395 * parameters are per cpu variables which have to be of the same size. A 396 * truth value is returned to indicate success or failure (since a double 397 * register result is difficult to handle). There is very limited hardware 398 * support for these operations, so only certain sizes may work. 399 */ 400 401 /* 402 * Operations for contexts where we do not want to do any checks for 403 * preemptions. Unless strictly necessary, always use [__]this_cpu_*() 404 * instead. 405 * 406 * If there is no other protection through preempt disable and/or disabling 407 * interupts then one of these RMW operations can show unexpected behavior 408 * because the execution thread was rescheduled on another processor or an 409 * interrupt occurred and the same percpu variable was modified from the 410 * interrupt context. 411 */ 412 #define raw_cpu_read(pcp) __pcpu_size_call_return(raw_cpu_read_, pcp) 413 #define raw_cpu_write(pcp, val) __pcpu_size_call(raw_cpu_write_, pcp, val) 414 #define raw_cpu_add(pcp, val) __pcpu_size_call(raw_cpu_add_, pcp, val) 415 #define raw_cpu_and(pcp, val) __pcpu_size_call(raw_cpu_and_, pcp, val) 416 #define raw_cpu_or(pcp, val) __pcpu_size_call(raw_cpu_or_, pcp, val) 417 #define raw_cpu_add_return(pcp, val) __pcpu_size_call_return2(raw_cpu_add_return_, pcp, val) 418 #define raw_cpu_xchg(pcp, nval) __pcpu_size_call_return2(raw_cpu_xchg_, pcp, nval) 419 #define raw_cpu_cmpxchg(pcp, oval, nval) \ 420 __pcpu_size_call_return2(raw_cpu_cmpxchg_, pcp, oval, nval) 421 #define raw_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2) \ 422 __pcpu_double_call_return_bool(raw_cpu_cmpxchg_double_, pcp1, pcp2, oval1, oval2, nval1, nval2) 423 424 #define raw_cpu_sub(pcp, val) raw_cpu_add(pcp, -(val)) 425 #define raw_cpu_inc(pcp) raw_cpu_add(pcp, 1) 426 #define raw_cpu_dec(pcp) raw_cpu_sub(pcp, 1) 427 #define raw_cpu_sub_return(pcp, val) raw_cpu_add_return(pcp, -(typeof(pcp))(val)) 428 #define raw_cpu_inc_return(pcp) raw_cpu_add_return(pcp, 1) 429 #define raw_cpu_dec_return(pcp) raw_cpu_add_return(pcp, -1) 430 431 /* 432 * Operations for contexts that are safe from preemption/interrupts. These 433 * operations verify that preemption is disabled. 434 */ 435 #define __this_cpu_read(pcp) \ 436 ({ \ 437 __this_cpu_preempt_check("read"); \ 438 raw_cpu_read(pcp); \ 439 }) 440 441 #define __this_cpu_write(pcp, val) \ 442 ({ \ 443 __this_cpu_preempt_check("write"); \ 444 raw_cpu_write(pcp, val); \ 445 }) 446 447 #define __this_cpu_add(pcp, val) \ 448 ({ \ 449 __this_cpu_preempt_check("add"); \ 450 raw_cpu_add(pcp, val); \ 451 }) 452 453 #define __this_cpu_and(pcp, val) \ 454 ({ \ 455 __this_cpu_preempt_check("and"); \ 456 raw_cpu_and(pcp, val); \ 457 }) 458 459 #define __this_cpu_or(pcp, val) \ 460 ({ \ 461 __this_cpu_preempt_check("or"); \ 462 raw_cpu_or(pcp, val); \ 463 }) 464 465 #define __this_cpu_add_return(pcp, val) \ 466 ({ \ 467 __this_cpu_preempt_check("add_return"); \ 468 raw_cpu_add_return(pcp, val); \ 469 }) 470 471 #define __this_cpu_xchg(pcp, nval) \ 472 ({ \ 473 __this_cpu_preempt_check("xchg"); \ 474 raw_cpu_xchg(pcp, nval); \ 475 }) 476 477 #define __this_cpu_cmpxchg(pcp, oval, nval) \ 478 ({ \ 479 __this_cpu_preempt_check("cmpxchg"); \ 480 raw_cpu_cmpxchg(pcp, oval, nval); \ 481 }) 482 483 #define __this_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2) \ 484 ({ __this_cpu_preempt_check("cmpxchg_double"); \ 485 raw_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2); \ 486 }) 487 488 #define __this_cpu_sub(pcp, val) __this_cpu_add(pcp, -(typeof(pcp))(val)) 489 #define __this_cpu_inc(pcp) __this_cpu_add(pcp, 1) 490 #define __this_cpu_dec(pcp) __this_cpu_sub(pcp, 1) 491 #define __this_cpu_sub_return(pcp, val) __this_cpu_add_return(pcp, -(typeof(pcp))(val)) 492 #define __this_cpu_inc_return(pcp) __this_cpu_add_return(pcp, 1) 493 #define __this_cpu_dec_return(pcp) __this_cpu_add_return(pcp, -1) 494 495 /* 496 * Operations with implied preemption protection. These operations can be 497 * used without worrying about preemption. Note that interrupts may still 498 * occur while an operation is in progress and if the interrupt modifies 499 * the variable too then RMW actions may not be reliable. 500 */ 501 #define this_cpu_read(pcp) __pcpu_size_call_return(this_cpu_read_, pcp) 502 #define this_cpu_write(pcp, val) __pcpu_size_call(this_cpu_write_, pcp, val) 503 #define this_cpu_add(pcp, val) __pcpu_size_call(this_cpu_add_, pcp, val) 504 #define this_cpu_and(pcp, val) __pcpu_size_call(this_cpu_and_, pcp, val) 505 #define this_cpu_or(pcp, val) __pcpu_size_call(this_cpu_or_, pcp, val) 506 #define this_cpu_add_return(pcp, val) __pcpu_size_call_return2(this_cpu_add_return_, pcp, val) 507 #define this_cpu_xchg(pcp, nval) __pcpu_size_call_return2(this_cpu_xchg_, pcp, nval) 508 #define this_cpu_cmpxchg(pcp, oval, nval) \ 509 __pcpu_size_call_return2(this_cpu_cmpxchg_, pcp, oval, nval) 510 #define this_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2) \ 511 __pcpu_double_call_return_bool(this_cpu_cmpxchg_double_, pcp1, pcp2, oval1, oval2, nval1, nval2) 512 513 #define this_cpu_sub(pcp, val) this_cpu_add(pcp, -(typeof(pcp))(val)) 514 #define this_cpu_inc(pcp) this_cpu_add(pcp, 1) 515 #define this_cpu_dec(pcp) this_cpu_sub(pcp, 1) 516 #define this_cpu_sub_return(pcp, val) this_cpu_add_return(pcp, -(typeof(pcp))(val)) 517 #define this_cpu_inc_return(pcp) this_cpu_add_return(pcp, 1) 518 #define this_cpu_dec_return(pcp) this_cpu_add_return(pcp, -1) 519 520 #endif /* __ASSEMBLY__ */ 521 #endif /* _LINUX_PERCPU_DEFS_H */ 522