include/linux/percpu-defs.h

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2 /*
   3  * linux/percpu-defs.h - basic definitions for percpu areas
   4  *
   5  * DO NOT INCLUDE DIRECTLY OUTSIDE PERCPU IMPLEMENTATION PROPER.
   6  *
   7  * This file is separate from linux/percpu.h to avoid cyclic inclusion
   8  * dependency from arch header files.  Only to be included from
   9  * asm/percpu.h.
  10  *
  11  * This file includes macros necessary to declare percpu sections and
  12  * variables, and definitions of percpu accessors and operations.  It
  13  * should provide enough percpu features to arch header files even when
  14  * they can only include asm/percpu.h to avoid cyclic inclusion dependency.
  15  */
  16
  17 #ifndef _LINUX_PERCPU_DEFS_H
  18 #define _LINUX_PERCPU_DEFS_H
  19
  20 #ifdef CONFIG_SMP
  21
  22 #ifdef MODULE
  23 #define PER_CPU_SHARED_ALIGNED_SECTION ""
  24 #define PER_CPU_ALIGNED_SECTION ""
  25 #else
  26 #define PER_CPU_SHARED_ALIGNED_SECTION "..shared_aligned"
  27 #define PER_CPU_ALIGNED_SECTION "..shared_aligned"
  28 #endif
  29 #define PER_CPU_FIRST_SECTION "..first"
  30
  31 #else
  32
  33 #define PER_CPU_SHARED_ALIGNED_SECTION ""
  34 #define PER_CPU_ALIGNED_SECTION "..shared_aligned"
  35 #define PER_CPU_FIRST_SECTION ""
  36
  37 #endif
  38
  39 /*
  40  * Base implementations of per-CPU variable declarations and definitions, where
  41  * the section in which the variable is to be placed is provided by the
  42  * 'sec' argument.  This may be used to affect the parameters governing the
  43  * variable's storage.
  44  *
  45  * NOTE!  The sections for the DECLARE and for the DEFINE must match, lest
  46  * linkage errors occur due the compiler generating the wrong code to access
  47  * that section.
  48  */
  49 #define __PCPU_ATTRS(sec)                                               \
  50         __percpu __attribute__((section(PER_CPU_BASE_SECTION sec)))     \
  51         PER_CPU_ATTRIBUTES
  52
  53 #define __PCPU_DUMMY_ATTRS                                              \
  54         __section(".discard") __attribute__((unused))
  55
  56 /*
  57  * s390 and alpha modules require percpu variables to be defined as
  58  * weak to force the compiler to generate GOT based external
  59  * references for them.  This is necessary because percpu sections
  60  * will be located outside of the usually addressable area.
  61  *
  62  * This definition puts the following two extra restrictions when
  63  * defining percpu variables.
  64  *
  65  * 1. The symbol must be globally unique, even the static ones.
  66  * 2. Static percpu variables cannot be defined inside a function.
  67  *
  68  * Archs which need weak percpu definitions should define
  69  * ARCH_NEEDS_WEAK_PER_CPU in asm/percpu.h when necessary.
  70  *
  71  * To ensure that the generic code observes the above two
  72  * restrictions, if CONFIG_DEBUG_FORCE_WEAK_PER_CPU is set weak
  73  * definition is used for all cases.
  74  */
  75 #if defined(ARCH_NEEDS_WEAK_PER_CPU) || defined(CONFIG_DEBUG_FORCE_WEAK_PER_CPU)
  76 /*
  77  * __pcpu_scope_* dummy variable is used to enforce scope.  It
  78  * receives the static modifier when it's used in front of
  79  * DEFINE_PER_CPU() and will trigger build failure if
  80  * DECLARE_PER_CPU() is used for the same variable.
  81  *
  82  * __pcpu_unique_* dummy variable is used to enforce symbol uniqueness
  83  * such that hidden weak symbol collision, which will cause unrelated
  84  * variables to share the same address, can be detected during build.
  85  */
  86 #define DECLARE_PER_CPU_SECTION(type, name, sec)                        \
  87         extern __PCPU_DUMMY_ATTRS char __pcpu_scope_##name;             \
  88         extern __PCPU_ATTRS(sec) __typeof__(type) name
  89
  90 #define DEFINE_PER_CPU_SECTION(type, name, sec)                         \
  91         __PCPU_DUMMY_ATTRS char __pcpu_scope_##name;                    \
  92         extern __PCPU_DUMMY_ATTRS char __pcpu_unique_##name;            \
  93         __PCPU_DUMMY_ATTRS char __pcpu_unique_##name;                   \
  94         extern __PCPU_ATTRS(sec) __typeof__(type) name;                 \
  95         __PCPU_ATTRS(sec) __weak __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) __typeof__(type) name
 105 #endif
 106
 107 /*
 108  * Variant on the per-CPU variable declaration/definition theme used for
 109  * ordinary per-CPU variables.
 110  */
 111 #define DECLARE_PER_CPU(type, name)                                     \
 112         DECLARE_PER_CPU_SECTION(type, name, "")
 113
 114 #define DEFINE_PER_CPU(type, name)                                      \
 115         DEFINE_PER_CPU_SECTION(type, name, "")
 116
 117 /*
 118  * Declaration/definition used for per-CPU variables that must come first in
 119  * the set of variables.
 120  */
 121 #define DECLARE_PER_CPU_FIRST(type, name)                               \
 122         DECLARE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)
 123
 124 #define DEFINE_PER_CPU_FIRST(type, name)                                \
 125         DEFINE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)
 126
 127 /*
 128  * Declaration/definition used for per-CPU variables that must be cacheline
 129  * aligned under SMP conditions so that, whilst a particular instance of the
 130  * data corresponds to a particular CPU, inefficiencies due to direct access by
 131  * other CPUs are reduced by preventing the data from unnecessarily spanning
 132  * cachelines.
 133  *
 134  * An example of this would be statistical data, where each CPU's set of data
 135  * is updated by that CPU alone, but the data from across all CPUs is collated
 136  * by a CPU processing a read from a proc file.
 137  */
 138 #define DECLARE_PER_CPU_SHARED_ALIGNED(type, name)                      \
 139         DECLARE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
 140         ____cacheline_aligned_in_smp
 141
 142 #define DEFINE_PER_CPU_SHARED_ALIGNED(type, name)                       \
 143         DEFINE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
 144         ____cacheline_aligned_in_smp
 145
 146 #define DECLARE_PER_CPU_ALIGNED(type, name)                             \
 147         DECLARE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION)    \
 148         ____cacheline_aligned
 149
 150 #define DEFINE_PER_CPU_ALIGNED(type, name)                              \
 151         DEFINE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION)     \
 152         ____cacheline_aligned
 153
 154 /*
 155  * Declaration/definition used for per-CPU variables that must be page aligned.
 156  */
 157 #define DECLARE_PER_CPU_PAGE_ALIGNED(type, name)                        \
 158         DECLARE_PER_CPU_SECTION(type, name, "..page_aligned")           \
 159         __aligned(PAGE_SIZE)
 160
 161 #define DEFINE_PER_CPU_PAGE_ALIGNED(type, name)                         \
 162         DEFINE_PER_CPU_SECTION(type, name, "..page_aligned")            \
 163         __aligned(PAGE_SIZE)
 164
 165 /*
 166  * Declaration/definition used for per-CPU variables that must be read mostly.
 167  */
 168 #define DECLARE_PER_CPU_READ_MOSTLY(type, name)                 \
 169         DECLARE_PER_CPU_SECTION(type, name, "..read_mostly")
 170
 171 #define DEFINE_PER_CPU_READ_MOSTLY(type, name)                          \
 172         DEFINE_PER_CPU_SECTION(type, name, "..read_mostly")
 173
 174 /*
 175  * Declaration/definition used for per-CPU variables that should be accessed
 176  * as decrypted when memory encryption is enabled in the guest.
 177  */
 178 #ifdef CONFIG_AMD_MEM_ENCRYPT
 179 #define DECLARE_PER_CPU_DECRYPTED(type, name)                           \
 180         DECLARE_PER_CPU_SECTION(type, name, "..decrypted")
 181
 182 #define DEFINE_PER_CPU_DECRYPTED(type, name)                            \
 183         DEFINE_PER_CPU_SECTION(type, name, "..decrypted")
 184 #else
 185 #define DEFINE_PER_CPU_DECRYPTED(type, name)    DEFINE_PER_CPU(type, name)
 186 #endif
 187
 188 /*
 189  * Intermodule exports for per-CPU variables.  sparse forgets about
 190  * address space across EXPORT_SYMBOL(), change EXPORT_SYMBOL() to
 191  * noop if __CHECKER__.
 192  */
 193 #ifndef __CHECKER__
 194 #define EXPORT_PER_CPU_SYMBOL(var) EXPORT_SYMBOL(var)
 195 #define EXPORT_PER_CPU_SYMBOL_GPL(var) EXPORT_SYMBOL_GPL(var)
 196 #else
 197 #define EXPORT_PER_CPU_SYMBOL(var)
 198 #define EXPORT_PER_CPU_SYMBOL_GPL(var)
 199 #endif
 200
 201 /*
 202  * Accessors and operations.
 203  */
 204 #ifndef __ASSEMBLY__
 205
 206 /*
 207  * __verify_pcpu_ptr() verifies @ptr is a percpu pointer without evaluating
 208  * @ptr and is invoked once before a percpu area is accessed by all
 209  * accessors and operations.  This is performed in the generic part of
 210  * percpu and arch overrides don't need to worry about it; however, if an
 211  * arch wants to implement an arch-specific percpu accessor or operation,
 212  * it may use __verify_pcpu_ptr() to verify the parameters.
 213  *
 214  * + 0 is required in order to convert the pointer type from a
 215  * potential array type to a pointer to a single item of the array.
 216  */
 217 #define __verify_pcpu_ptr(ptr)                                          \
 218 do {                                                                    \
 219         const void __percpu *__vpp_verify = (typeof((ptr) + 0))NULL;    \
 220         (void)__vpp_verify;                                             \
 221 } while (0)
 222
 223 #ifdef CONFIG_SMP
 224
 225 /*
 226  * Add an offset to a pointer but keep the pointer as-is.  Use RELOC_HIDE()
 227  * to prevent the compiler from making incorrect assumptions about the
 228  * pointer value.  The weird cast keeps both GCC and sparse happy.
 229  */
 230 #define SHIFT_PERCPU_PTR(__p, __offset)                                 \
 231         RELOC_HIDE((typeof(*(__p)) __kernel __force *)(__p), (__offset))
 232
 233 #define per_cpu_ptr(ptr, cpu)                                           \
 234 ({                                                                      \
 235         __verify_pcpu_ptr(ptr);                                         \
 236         SHIFT_PERCPU_PTR((ptr), per_cpu_offset((cpu)));                 \
 237 })
 238
 239 #define raw_cpu_ptr(ptr)                                                \
 240 ({                                                                      \
 241         __verify_pcpu_ptr(ptr);                                         \
 242         arch_raw_cpu_ptr(ptr);                                          \
 243 })
 244
 245 #ifdef CONFIG_DEBUG_PREEMPT
 246 #define this_cpu_ptr(ptr)                                               \
 247 ({                                                                      \
 248         __verify_pcpu_ptr(ptr);                                         \
 249         SHIFT_PERCPU_PTR(ptr, my_cpu_offset);                           \
 250 })
 251 #else
 252 #define this_cpu_ptr(ptr) raw_cpu_ptr(ptr)
 253 #endif
 254
 255 #else   /* CONFIG_SMP */
 256
 257 #define VERIFY_PERCPU_PTR(__p)                                          \
 258 ({                                                                      \
 259         __verify_pcpu_ptr(__p);                                         \
 260         (typeof(*(__p)) __kernel __force *)(__p);                       \
 261 })
 262
 263 #define per_cpu_ptr(ptr, cpu)   ({ (void)(cpu); VERIFY_PERCPU_PTR(ptr); })
 264 #define raw_cpu_ptr(ptr)        per_cpu_ptr(ptr, 0)
 265 #define this_cpu_ptr(ptr)       raw_cpu_ptr(ptr)
 266
 267 #endif  /* CONFIG_SMP */
 268
 269 #define per_cpu(var, cpu)       (*per_cpu_ptr(&(var), cpu))
 270
 271 /*
 272  * Must be an lvalue. Since @var must be a simple identifier,
 273  * we force a syntax error here if it isn't.
 274  */
 275 #define get_cpu_var(var)                                                \
 276 (*({                                                                    \
 277         preempt_disable();                                              \
 278         this_cpu_ptr(&var);                                             \
 279 }))
 280
 281 /*
 282  * The weird & is necessary because sparse considers (void)(var) to be
 283  * a direct dereference of percpu variable (var).
 284  */
 285 #define put_cpu_var(var)                                                \
 286 do {                                                                    \
 287         (void)&(var);                                                   \
 288         preempt_enable();                                               \
 289 } while (0)
 290
 291 #define get_cpu_ptr(var)                                                \
 292 ({                                                                      \
 293         preempt_disable();                                              \
 294         this_cpu_ptr(var);                                              \
 295 })
 296
 297 #define put_cpu_ptr(var)                                                \
 298 do {                                                                    \
 299         (void)(var);                                                    \
 300         preempt_enable();                                               \
 301 } while (0)
 302
 303 /*
 304  * Branching function to split up a function into a set of functions that
 305  * are called for different scalar sizes of the objects handled.
 306  */
 307
 308 extern void __bad_size_call_parameter(void);
 309
 310 #ifdef CONFIG_DEBUG_PREEMPT
 311 extern void __this_cpu_preempt_check(const char *op);
 312 #else
 313 static __always_inline void __this_cpu_preempt_check(const char *op) { }
 314 #endif
 315
 316 #define __pcpu_size_call_return(stem, variable)                         \
 317 ({                                                                      \
 318         typeof(variable) pscr_ret__;                                    \
 319         __verify_pcpu_ptr(&(variable));                                 \
 320         switch(sizeof(variable)) {                                      \
 321         case 1: pscr_ret__ = stem##1(variable); break;                  \
 322         case 2: pscr_ret__ = stem##2(variable); break;                  \
 323         case 4: pscr_ret__ = stem##4(variable); break;                  \
 324         case 8: pscr_ret__ = stem##8(variable); break;                  \
 325         default:                                                        \
 326                 __bad_size_call_parameter(); break;                     \
 327         }                                                               \
 328         pscr_ret__;                                                     \
 329 })
 330
 331 #define __pcpu_size_call_return2(stem, variable, ...)                   \
 332 ({                                                                      \
 333         typeof(variable) pscr2_ret__;                                   \
 334         __verify_pcpu_ptr(&(variable));                                 \
 335         switch(sizeof(variable)) {                                      \
 336         case 1: pscr2_ret__ = stem##1(variable, __VA_ARGS__); break;    \
 337         case 2: pscr2_ret__ = stem##2(variable, __VA_ARGS__); break;    \
 338         case 4: pscr2_ret__ = stem##4(variable, __VA_ARGS__); break;    \
 339         case 8: pscr2_ret__ = stem##8(variable, __VA_ARGS__); break;    \
 340         default:                                                        \
 341                 __bad_size_call_parameter(); break;                     \
 342         }                                                               \
 343         pscr2_ret__;                                                    \
 344 })
 345
 346 #define __pcpu_size_call_return2bool(stem, variable, ...)               \
 347 ({                                                                      \
 348         bool pscr2_ret__;                                               \
 349         __verify_pcpu_ptr(&(variable));                                 \
 350         switch(sizeof(variable)) {                                      \
 351         case 1: pscr2_ret__ = stem##1(variable, __VA_ARGS__); break;    \
 352         case 2: pscr2_ret__ = stem##2(variable, __VA_ARGS__); break;    \
 353         case 4: pscr2_ret__ = stem##4(variable, __VA_ARGS__); break;    \
 354         case 8: pscr2_ret__ = stem##8(variable, __VA_ARGS__); break;    \
 355         default:                                                        \
 356                 __bad_size_call_parameter(); break;                     \
 357         }                                                               \
 358         pscr2_ret__;                                                    \
 359 })
 360
 361 #define __pcpu_size_call(stem, variable, ...)                           \
 362 do {                                                                    \
 363         __verify_pcpu_ptr(&(variable));                                 \
 364         switch(sizeof(variable)) {                                      \
 365                 case 1: stem##1(variable, __VA_ARGS__);break;           \
 366                 case 2: stem##2(variable, __VA_ARGS__);break;           \
 367                 case 4: stem##4(variable, __VA_ARGS__);break;           \
 368                 case 8: stem##8(variable, __VA_ARGS__);break;           \
 369                 default:                                                \
 370                         __bad_size_call_parameter();break;              \
 371         }                                                               \
 372 } while (0)
 373
 374 /*
 375  * this_cpu operations (C) 2008-2013 Christoph Lameter <[email protected]>
 376  *
 377  * Optimized manipulation for memory allocated through the per cpu
 378  * allocator or for addresses of per cpu variables.
 379  *
 380  * These operation guarantee exclusivity of access for other operations
 381  * on the *same* processor. The assumption is that per cpu data is only
 382  * accessed by a single processor instance (the current one).
 383  *
 384  * The arch code can provide optimized implementation by defining macros
 385  * for certain scalar sizes. F.e. provide this_cpu_add_2() to provide per
 386  * cpu atomic operations for 2 byte sized RMW actions. If arch code does
 387  * not provide operations for a scalar size then the fallback in the
 388  * generic code will be used.
 389  *
 390  * cmpxchg_double replaces two adjacent scalars at once.  The first two
 391  * parameters are per cpu variables which have to be of the same size.  A
 392  * truth value is returned to indicate success or failure (since a double
 393  * register result is difficult to handle).  There is very limited hardware
 394  * support for these operations, so only certain sizes may work.
 395  */
 396
 397 /*
 398  * Operations for contexts where we do not want to do any checks for
 399  * preemptions.  Unless strictly necessary, always use [__]this_cpu_*()
 400  * instead.
 401  *
 402  * If there is no other protection through preempt disable and/or disabling
 403  * interrupts then one of these RMW operations can show unexpected behavior
 404  * because the execution thread was rescheduled on another processor or an
 405  * interrupt occurred and the same percpu variable was modified from the
 406  * interrupt context.
 407  */
 408 #define raw_cpu_read(pcp)               __pcpu_size_call_return(raw_cpu_read_, pcp)
 409 #define raw_cpu_write(pcp, val)         __pcpu_size_call(raw_cpu_write_, pcp, val)
 410 #define raw_cpu_add(pcp, val)           __pcpu_size_call(raw_cpu_add_, pcp, val)
 411 #define raw_cpu_and(pcp, val)           __pcpu_size_call(raw_cpu_and_, pcp, val)
 412 #define raw_cpu_or(pcp, val)            __pcpu_size_call(raw_cpu_or_, pcp, val)
 413 #define raw_cpu_add_return(pcp, val)    __pcpu_size_call_return2(raw_cpu_add_return_, pcp, val)
 414 #define raw_cpu_xchg(pcp, nval)         __pcpu_size_call_return2(raw_cpu_xchg_, pcp, nval)
 415 #define raw_cpu_cmpxchg(pcp, oval, nval) \
 416         __pcpu_size_call_return2(raw_cpu_cmpxchg_, pcp, oval, nval)
 417 #define raw_cpu_try_cmpxchg(pcp, ovalp, nval) \
 418         __pcpu_size_call_return2bool(raw_cpu_try_cmpxchg_, pcp, ovalp, nval)
 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_sub(pcp, val)        __this_cpu_add(pcp, -(typeof(pcp))(val))
 479 #define __this_cpu_inc(pcp)             __this_cpu_add(pcp, 1)
 480 #define __this_cpu_dec(pcp)             __this_cpu_sub(pcp, 1)
 481 #define __this_cpu_sub_return(pcp, val) __this_cpu_add_return(pcp, -(typeof(pcp))(val))
 482 #define __this_cpu_inc_return(pcp)      __this_cpu_add_return(pcp, 1)
 483 #define __this_cpu_dec_return(pcp)      __this_cpu_add_return(pcp, -1)
 484
 485 /*
 486  * Operations with implied preemption/interrupt protection.  These
 487  * operations can be used without worrying about preemption or interrupt.
 488  */
 489 #define this_cpu_read(pcp)              __pcpu_size_call_return(this_cpu_read_, pcp)
 490 #define this_cpu_write(pcp, val)        __pcpu_size_call(this_cpu_write_, pcp, val)
 491 #define this_cpu_add(pcp, val)          __pcpu_size_call(this_cpu_add_, pcp, val)
 492 #define this_cpu_and(pcp, val)          __pcpu_size_call(this_cpu_and_, pcp, val)
 493 #define this_cpu_or(pcp, val)           __pcpu_size_call(this_cpu_or_, pcp, val)
 494 #define this_cpu_add_return(pcp, val)   __pcpu_size_call_return2(this_cpu_add_return_, pcp, val)
 495 #define this_cpu_xchg(pcp, nval)        __pcpu_size_call_return2(this_cpu_xchg_, pcp, nval)
 496 #define this_cpu_cmpxchg(pcp, oval, nval) \
 497         __pcpu_size_call_return2(this_cpu_cmpxchg_, pcp, oval, nval)
 498 #define this_cpu_try_cmpxchg(pcp, ovalp, nval) \
 499         __pcpu_size_call_return2bool(this_cpu_try_cmpxchg_, pcp, ovalp, nval)
 500 #define this_cpu_sub(pcp, val)          this_cpu_add(pcp, -(typeof(pcp))(val))
 501 #define this_cpu_inc(pcp)               this_cpu_add(pcp, 1)
 502 #define this_cpu_dec(pcp)               this_cpu_sub(pcp, 1)
 503 #define this_cpu_sub_return(pcp, val)   this_cpu_add_return(pcp, -(typeof(pcp))(val))
 504 #define this_cpu_inc_return(pcp)        this_cpu_add_return(pcp, 1)
 505 #define this_cpu_dec_return(pcp)        this_cpu_add_return(pcp, -1)
 506
 507 #endif /* __ASSEMBLY__ */
 508 #endif /* _LINUX_PERCPU_DEFS_H */