개념 설명 전체 · v6.18.37 / include/linux/spinlock.h
1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef __LINUX_SPINLOCK_H 3 #define __LINUX_SPINLOCK_H 4 #define __LINUX_INSIDE_SPINLOCK_H 5 6 /* 7 * include/linux/spinlock.h - generic spinlock/rwlock declarations 8 * 9 * here's the role of the various spinlock/rwlock related include files: 10 * 11 * on SMP builds: 12 * 13 * asm/spinlock_types.h: contains the arch_spinlock_t/arch_rwlock_t and the 14 * initializers 15 * 16 * linux/spinlock_types_raw: 17 * The raw types and initializers 18 * linux/spinlock_types.h: 19 * defines the generic type and initializers 20 * 21 * asm/spinlock.h: contains the arch_spin_*()/etc. lowlevel 22 * implementations, mostly inline assembly code 23 * 24 * (also included on UP-debug builds:) 25 * 26 * linux/spinlock_api_smp.h: 27 * contains the prototypes for the _spin_*() APIs. 28 * 29 * linux/spinlock.h: builds the final spin_*() APIs. 30 * 31 * on UP builds: 32 * 33 * linux/spinlock_type_up.h: 34 * contains the generic, simplified UP spinlock type. 35 * (which is an empty structure on non-debug builds) 36 * 37 * linux/spinlock_types_raw: 38 * The raw RT types and initializers 39 * linux/spinlock_types.h: 40 * defines the generic type and initializers 41 * 42 * linux/spinlock_up.h: 43 * contains the arch_spin_*()/etc. version of UP 44 * builds. (which are NOPs on non-debug, non-preempt 45 * builds) 46 * 47 * (included on UP-non-debug builds:) 48 * 49 * linux/spinlock_api_up.h: 50 * builds the _spin_*() APIs. 51 * 52 * linux/spinlock.h: builds the final spin_*() APIs. 53 */ 54 55 #include <linux/typecheck.h> 56 #include <linux/preempt.h> 57 #include <linux/linkage.h> 58 #include <linux/compiler.h> 59 #include <linux/irqflags.h> 60 #include <linux/thread_info.h> 61 #include <linux/stringify.h> 62 #include <linux/bottom_half.h> 63 #include <linux/lockdep.h> 64 #include <linux/cleanup.h> 65 #include <asm/barrier.h> 66 #include <asm/mmiowb.h> 67 68 69 /* 70 * Must define these before including other files, inline functions need them 71 */ 72 #define LOCK_SECTION_NAME ".text..lock."KBUILD_BASENAME 73 74 #define LOCK_SECTION_START(extra) \ 75 ".subsection 1\n\t" \ 76 extra \ 77 ".ifndef " LOCK_SECTION_NAME "\n\t" \ 78 LOCK_SECTION_NAME ":\n\t" \ 79 ".endif\n" 80 81 #define LOCK_SECTION_END \ 82 ".previous\n\t" 83 84 #define __lockfunc __section(".spinlock.text") 85 86 /* 87 * Pull the arch_spinlock_t and arch_rwlock_t definitions: 88 */ 89 #include <linux/spinlock_types.h> 90 91 /* 92 * Pull the arch_spin*() functions/declarations (UP-nondebug doesn't need them): 93 */ 94 #ifdef CONFIG_SMP 95 # include <asm/spinlock.h> 96 #else 97 # include <linux/spinlock_up.h> 98 #endif 99 100 #ifdef CONFIG_DEBUG_SPINLOCK 101 extern void __raw_spin_lock_init(raw_spinlock_t *lock, const char *name, 102 struct lock_class_key *key, short inner); 103 104 # define raw_spin_lock_init(lock) \ 105 do { \ 106 static struct lock_class_key __key; \ 107 \ 108 __raw_spin_lock_init((lock), #lock, &__key, LD_WAIT_SPIN); \ 109 } while (0) 110 111 #else 112 # define raw_spin_lock_init(lock) \ 113 do { *(lock) = __RAW_SPIN_LOCK_UNLOCKED(lock); } while (0) 114 #endif 115 116 #define raw_spin_is_locked(lock) arch_spin_is_locked(&(lock)->raw_lock) 117 118 #ifdef arch_spin_is_contended 119 #define raw_spin_is_contended(lock) arch_spin_is_contended(&(lock)->raw_lock) 120 #else 121 #define raw_spin_is_contended(lock) (((void)(lock), 0)) 122 #endif /*arch_spin_is_contended*/ 123 124 /* 125 * smp_mb__after_spinlock() provides the equivalent of a full memory barrier 126 * between program-order earlier lock acquisitions and program-order later 127 * memory accesses. 128 * 129 * This guarantees that the following two properties hold: 130 * 131 * 1) Given the snippet: 132 * 133 * { X = 0; Y = 0; } 134 * 135 * CPU0 CPU1 136 * 137 * WRITE_ONCE(X, 1); WRITE_ONCE(Y, 1); 138 * spin_lock(S); smp_mb(); 139 * smp_mb__after_spinlock(); r1 = READ_ONCE(X); 140 * r0 = READ_ONCE(Y); 141 * spin_unlock(S); 142 * 143 * it is forbidden that CPU0 does not observe CPU1's store to Y (r0 = 0) 144 * and CPU1 does not observe CPU0's store to X (r1 = 0); see the comments 145 * preceding the call to smp_mb__after_spinlock() in __schedule() and in 146 * try_to_wake_up(). 147 * 148 * 2) Given the snippet: 149 * 150 * { X = 0; Y = 0; } 151 * 152 * CPU0 CPU1 CPU2 153 * 154 * spin_lock(S); spin_lock(S); r1 = READ_ONCE(Y); 155 * WRITE_ONCE(X, 1); smp_mb__after_spinlock(); smp_rmb(); 156 * spin_unlock(S); r0 = READ_ONCE(X); r2 = READ_ONCE(X); 157 * WRITE_ONCE(Y, 1); 158 * spin_unlock(S); 159 * 160 * it is forbidden that CPU0's critical section executes before CPU1's 161 * critical section (r0 = 1), CPU2 observes CPU1's store to Y (r1 = 1) 162 * and CPU2 does not observe CPU0's store to X (r2 = 0); see the comments 163 * preceding the calls to smp_rmb() in try_to_wake_up() for similar 164 * snippets but "projected" onto two CPUs. 165 * 166 * Property (2) upgrades the lock to an RCsc lock. 167 * 168 * Since most load-store architectures implement ACQUIRE with an smp_mb() after 169 * the LL/SC loop, they need no further barriers. Similarly all our TSO 170 * architectures imply an smp_mb() for each atomic instruction and equally don't 171 * need more. 172 * 173 * Architectures that can implement ACQUIRE better need to take care. 174 */ 175 #ifndef smp_mb__after_spinlock 176 #define smp_mb__after_spinlock() kcsan_mb() 177 #endif 178 179 #ifdef CONFIG_DEBUG_SPINLOCK 180 extern void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock); 181 extern int do_raw_spin_trylock(raw_spinlock_t *lock); 182 extern void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock); 183 #else 184 static inline void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock) 185 { 186 __acquire(lock); 187 arch_spin_lock(&lock->raw_lock); 188 mmiowb_spin_lock(); 189 } 190 191 static inline int do_raw_spin_trylock(raw_spinlock_t *lock) 192 { 193 int ret = arch_spin_trylock(&(lock)->raw_lock); 194 195 if (ret) 196 mmiowb_spin_lock(); 197 198 return ret; 199 } 200 201 static inline void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock) 202 { 203 mmiowb_spin_unlock(); 204 arch_spin_unlock(&lock->raw_lock); 205 __release(lock); 206 } 207 #endif 208 209 /* 210 * Define the various spin_lock methods. Note we define these 211 * regardless of whether CONFIG_SMP or CONFIG_PREEMPTION are set. The 212 * various methods are defined as nops in the case they are not 213 * required. 214 */ 215 #define raw_spin_trylock(lock) __cond_lock(lock, _raw_spin_trylock(lock)) 216 217 #define raw_spin_lock(lock) _raw_spin_lock(lock) 218 219 #ifdef CONFIG_DEBUG_LOCK_ALLOC 220 # define raw_spin_lock_nested(lock, subclass) \ 221 _raw_spin_lock_nested(lock, subclass) 222 223 # define raw_spin_lock_nest_lock(lock, nest_lock) \ 224 do { \ 225 typecheck(struct lockdep_map *, &(nest_lock)->dep_map);\ 226 _raw_spin_lock_nest_lock(lock, &(nest_lock)->dep_map); \ 227 } while (0) 228 #else 229 /* 230 * Always evaluate the 'subclass' argument to avoid that the compiler 231 * warns about set-but-not-used variables when building with 232 * CONFIG_DEBUG_LOCK_ALLOC=n and with W=1. 233 */ 234 # define raw_spin_lock_nested(lock, subclass) \ 235 _raw_spin_lock(((void)(subclass), (lock))) 236 # define raw_spin_lock_nest_lock(lock, nest_lock) _raw_spin_lock(lock) 237 #endif 238 239 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) 240 241 #define raw_spin_lock_irqsave(lock, flags) \ 242 do { \ 243 typecheck(unsigned long, flags); \ 244 flags = _raw_spin_lock_irqsave(lock); \ 245 } while (0) 246 247 #ifdef CONFIG_DEBUG_LOCK_ALLOC 248 #define raw_spin_lock_irqsave_nested(lock, flags, subclass) \ 249 do { \ 250 typecheck(unsigned long, flags); \ 251 flags = _raw_spin_lock_irqsave_nested(lock, subclass); \ 252 } while (0) 253 #else 254 #define raw_spin_lock_irqsave_nested(lock, flags, subclass) \ 255 do { \ 256 typecheck(unsigned long, flags); \ 257 flags = _raw_spin_lock_irqsave(lock); \ 258 } while (0) 259 #endif 260 261 #else 262 263 #define raw_spin_lock_irqsave(lock, flags) \ 264 do { \ 265 typecheck(unsigned long, flags); \ 266 _raw_spin_lock_irqsave(lock, flags); \ 267 } while (0) 268 269 #define raw_spin_lock_irqsave_nested(lock, flags, subclass) \ 270 raw_spin_lock_irqsave(lock, flags) 271 272 #endif 273 274 #define raw_spin_lock_irq(lock) _raw_spin_lock_irq(lock) 275 #define raw_spin_lock_bh(lock) _raw_spin_lock_bh(lock) 276 #define raw_spin_unlock(lock) _raw_spin_unlock(lock) 277 #define raw_spin_unlock_irq(lock) _raw_spin_unlock_irq(lock) 278 279 #define raw_spin_unlock_irqrestore(lock, flags) \ 280 do { \ 281 typecheck(unsigned long, flags); \ 282 _raw_spin_unlock_irqrestore(lock, flags); \ 283 } while (0) 284 #define raw_spin_unlock_bh(lock) _raw_spin_unlock_bh(lock) 285 286 #define raw_spin_trylock_bh(lock) \ 287 __cond_lock(lock, _raw_spin_trylock_bh(lock)) 288 289 #define raw_spin_trylock_irq(lock) \ 290 ({ \ 291 local_irq_disable(); \ 292 raw_spin_trylock(lock) ? \ 293 1 : ({ local_irq_enable(); 0; }); \ 294 }) 295 296 #define raw_spin_trylock_irqsave(lock, flags) \ 297 ({ \ 298 local_irq_save(flags); \ 299 raw_spin_trylock(lock) ? \ 300 1 : ({ local_irq_restore(flags); 0; }); \ 301 }) 302 303 #ifndef CONFIG_PREEMPT_RT 304 /* Include rwlock functions for !RT */ 305 #include <linux/rwlock.h> 306 #endif 307 308 /* 309 * Pull the _spin_*()/_read_*()/_write_*() functions/declarations: 310 */ 311 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) 312 # include <linux/spinlock_api_smp.h> 313 #else 314 # include <linux/spinlock_api_up.h> 315 #endif 316 317 /* Non PREEMPT_RT kernel, map to raw spinlocks: */ 318 #ifndef CONFIG_PREEMPT_RT 319 320 /* 321 * Map the spin_lock functions to the raw variants for PREEMPT_RT=n 322 */ 323 324 static __always_inline raw_spinlock_t *spinlock_check(spinlock_t *lock) 325 { 326 return &lock->rlock; 327 } 328 329 #ifdef CONFIG_DEBUG_SPINLOCK 330 331 # define spin_lock_init(lock) \ 332 do { \ 333 static struct lock_class_key __key; \ 334 \ 335 __raw_spin_lock_init(spinlock_check(lock), \ 336 #lock, &__key, LD_WAIT_CONFIG); \ 337 } while (0) 338 339 #else 340 341 # define spin_lock_init(_lock) \ 342 do { \ 343 spinlock_check(_lock); \ 344 *(_lock) = __SPIN_LOCK_UNLOCKED(_lock); \ 345 } while (0) 346 347 #endif 348 349 static __always_inline void spin_lock(spinlock_t *lock) 350 { 351 raw_spin_lock(&lock->rlock); 352 } 353 354 static __always_inline void spin_lock_bh(spinlock_t *lock) 355 { 356 raw_spin_lock_bh(&lock->rlock); 357 } 358 359 static __always_inline int spin_trylock(spinlock_t *lock) 360 { 361 return raw_spin_trylock(&lock->rlock); 362 } 363 364 #define spin_lock_nested(lock, subclass) \ 365 do { \ 366 raw_spin_lock_nested(spinlock_check(lock), subclass); \ 367 } while (0) 368 369 #define spin_lock_nest_lock(lock, nest_lock) \ 370 do { \ 371 raw_spin_lock_nest_lock(spinlock_check(lock), nest_lock); \ 372 } while (0) 373 374 static __always_inline void spin_lock_irq(spinlock_t *lock) 375 { 376 raw_spin_lock_irq(&lock->rlock); 377 } 378 379 #define spin_lock_irqsave(lock, flags) \ 380 do { \ 381 raw_spin_lock_irqsave(spinlock_check(lock), flags); \ 382 } while (0) 383 384 #define spin_lock_irqsave_nested(lock, flags, subclass) \ 385 do { \ 386 raw_spin_lock_irqsave_nested(spinlock_check(lock), flags, subclass); \ 387 } while (0) 388 389 static __always_inline void spin_unlock(spinlock_t *lock) 390 { 391 raw_spin_unlock(&lock->rlock); 392 } 393 394 static __always_inline void spin_unlock_bh(spinlock_t *lock) 395 { 396 raw_spin_unlock_bh(&lock->rlock); 397 } 398 399 static __always_inline void spin_unlock_irq(spinlock_t *lock) 400 { 401 raw_spin_unlock_irq(&lock->rlock); 402 } 403 404 static __always_inline void spin_unlock_irqrestore(spinlock_t *lock, unsigned long flags) 405 { 406 raw_spin_unlock_irqrestore(&lock->rlock, flags); 407 } 408 409 static __always_inline int spin_trylock_bh(spinlock_t *lock) 410 { 411 return raw_spin_trylock_bh(&lock->rlock); 412 } 413 414 static __always_inline int spin_trylock_irq(spinlock_t *lock) 415 { 416 return raw_spin_trylock_irq(&lock->rlock); 417 } 418 419 #define spin_trylock_irqsave(lock, flags) \ 420 ({ \ 421 raw_spin_trylock_irqsave(spinlock_check(lock), flags); \ 422 }) 423 424 /** 425 * spin_is_locked() - Check whether a spinlock is locked. 426 * @lock: Pointer to the spinlock. 427 * 428 * This function is NOT required to provide any memory ordering 429 * guarantees; it could be used for debugging purposes or, when 430 * additional synchronization is needed, accompanied with other 431 * constructs (memory barriers) enforcing the synchronization. 432 * 433 * Returns: 1 if @lock is locked, 0 otherwise. 434 * 435 * Note that the function only tells you that the spinlock is 436 * seen to be locked, not that it is locked on your CPU. 437 * 438 * Further, on CONFIG_SMP=n builds with CONFIG_DEBUG_SPINLOCK=n, 439 * the return value is always 0 (see include/linux/spinlock_up.h). 440 * Therefore you should not rely heavily on the return value. 441 */ 442 static __always_inline int spin_is_locked(spinlock_t *lock) 443 { 444 return raw_spin_is_locked(&lock->rlock); 445 } 446 447 static __always_inline int spin_is_contended(spinlock_t *lock) 448 { 449 return raw_spin_is_contended(&lock->rlock); 450 } 451 452 #define assert_spin_locked(lock) assert_raw_spin_locked(&(lock)->rlock) 453 454 #else /* !CONFIG_PREEMPT_RT */ 455 # include <linux/spinlock_rt.h> 456 #endif /* CONFIG_PREEMPT_RT */ 457 458 /* 459 * Does a critical section need to be broken due to another 460 * task waiting?: (technically does not depend on CONFIG_PREEMPTION, 461 * but a general need for low latency) 462 */ 463 static inline int spin_needbreak(spinlock_t *lock) 464 { 465 if (!preempt_model_preemptible()) 466 return 0; 467 468 return spin_is_contended(lock); 469 } 470 471 /* 472 * Check if a rwlock is contended. 473 * Returns non-zero if there is another task waiting on the rwlock. 474 * Returns zero if the lock is not contended or the system / underlying 475 * rwlock implementation does not support contention detection. 476 * Technically does not depend on CONFIG_PREEMPTION, but a general need 477 * for low latency. 478 */ 479 static inline int rwlock_needbreak(rwlock_t *lock) 480 { 481 if (!preempt_model_preemptible()) 482 return 0; 483 484 return rwlock_is_contended(lock); 485 } 486 487 /* 488 * Pull the atomic_t declaration: 489 * (asm-mips/atomic.h needs above definitions) 490 */ 491 #include <linux/atomic.h> 492 /** 493 * atomic_dec_and_lock - lock on reaching reference count zero 494 * @atomic: the atomic counter 495 * @lock: the spinlock in question 496 * 497 * Decrements @atomic by 1. If the result is 0, returns true and locks 498 * @lock. Returns false for all other cases. 499 */ 500 extern int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock); 501 #define atomic_dec_and_lock(atomic, lock) \ 502 __cond_lock(lock, _atomic_dec_and_lock(atomic, lock)) 503 504 extern int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock, 505 unsigned long *flags); 506 #define atomic_dec_and_lock_irqsave(atomic, lock, flags) \ 507 __cond_lock(lock, _atomic_dec_and_lock_irqsave(atomic, lock, &(flags))) 508 509 extern int _atomic_dec_and_raw_lock(atomic_t *atomic, raw_spinlock_t *lock); 510 #define atomic_dec_and_raw_lock(atomic, lock) \ 511 __cond_lock(lock, _atomic_dec_and_raw_lock(atomic, lock)) 512 513 extern int _atomic_dec_and_raw_lock_irqsave(atomic_t *atomic, raw_spinlock_t *lock, 514 unsigned long *flags); 515 #define atomic_dec_and_raw_lock_irqsave(atomic, lock, flags) \ 516 __cond_lock(lock, _atomic_dec_and_raw_lock_irqsave(atomic, lock, &(flags))) 517 518 int __alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *lock_mask, 519 size_t max_size, unsigned int cpu_mult, 520 gfp_t gfp, const char *name, 521 struct lock_class_key *key); 522 523 #define alloc_bucket_spinlocks(locks, lock_mask, max_size, cpu_mult, gfp) \ 524 ({ \ 525 static struct lock_class_key key; \ 526 int ret; \ 527 \ 528 ret = __alloc_bucket_spinlocks(locks, lock_mask, max_size, \ 529 cpu_mult, gfp, #locks, &key); \ 530 ret; \ 531 }) 532 533 void free_bucket_spinlocks(spinlock_t *locks); 534 535 DEFINE_LOCK_GUARD_1(raw_spinlock, raw_spinlock_t, 536 raw_spin_lock(_T->lock), 537 raw_spin_unlock(_T->lock)) 538 539 DEFINE_LOCK_GUARD_1_COND(raw_spinlock, _try, raw_spin_trylock(_T->lock)) 540 541 DEFINE_LOCK_GUARD_1(raw_spinlock_nested, raw_spinlock_t, 542 raw_spin_lock_nested(_T->lock, SINGLE_DEPTH_NESTING), 543 raw_spin_unlock(_T->lock)) 544 545 DEFINE_LOCK_GUARD_1(raw_spinlock_irq, raw_spinlock_t, 546 raw_spin_lock_irq(_T->lock), 547 raw_spin_unlock_irq(_T->lock)) 548 549 DEFINE_LOCK_GUARD_1_COND(raw_spinlock_irq, _try, raw_spin_trylock_irq(_T->lock)) 550 551 DEFINE_LOCK_GUARD_1(raw_spinlock_bh, raw_spinlock_t, 552 raw_spin_lock_bh(_T->lock), 553 raw_spin_unlock_bh(_T->lock)) 554 555 DEFINE_LOCK_GUARD_1_COND(raw_spinlock_bh, _try, raw_spin_trylock_bh(_T->lock)) 556 557 DEFINE_LOCK_GUARD_1(raw_spinlock_irqsave, raw_spinlock_t, 558 raw_spin_lock_irqsave(_T->lock, _T->flags), 559 raw_spin_unlock_irqrestore(_T->lock, _T->flags), 560 unsigned long flags) 561 562 DEFINE_LOCK_GUARD_1_COND(raw_spinlock_irqsave, _try, 563 raw_spin_trylock_irqsave(_T->lock, _T->flags)) 564 565 DEFINE_LOCK_GUARD_1(spinlock, spinlock_t, 566 spin_lock(_T->lock), 567 spin_unlock(_T->lock)) 568 569 DEFINE_LOCK_GUARD_1_COND(spinlock, _try, spin_trylock(_T->lock)) 570 571 DEFINE_LOCK_GUARD_1(spinlock_irq, spinlock_t, 572 spin_lock_irq(_T->lock), 573 spin_unlock_irq(_T->lock)) 574 575 DEFINE_LOCK_GUARD_1_COND(spinlock_irq, _try, 576 spin_trylock_irq(_T->lock)) 577 578 DEFINE_LOCK_GUARD_1(spinlock_bh, spinlock_t, 579 spin_lock_bh(_T->lock), 580 spin_unlock_bh(_T->lock)) 581 582 DEFINE_LOCK_GUARD_1_COND(spinlock_bh, _try, 583 spin_trylock_bh(_T->lock)) 584 585 DEFINE_LOCK_GUARD_1(spinlock_irqsave, spinlock_t, 586 spin_lock_irqsave(_T->lock, _T->flags), 587 spin_unlock_irqrestore(_T->lock, _T->flags), 588 unsigned long flags) 589 590 DEFINE_LOCK_GUARD_1_COND(spinlock_irqsave, _try, 591 spin_trylock_irqsave(_T->lock, _T->flags)) 592 593 DEFINE_LOCK_GUARD_1(read_lock, rwlock_t, 594 read_lock(_T->lock), 595 read_unlock(_T->lock)) 596 597 DEFINE_LOCK_GUARD_1(read_lock_irq, rwlock_t, 598 read_lock_irq(_T->lock), 599 read_unlock_irq(_T->lock)) 600 601 DEFINE_LOCK_GUARD_1(read_lock_irqsave, rwlock_t, 602 read_lock_irqsave(_T->lock, _T->flags), 603 read_unlock_irqrestore(_T->lock, _T->flags), 604 unsigned long flags) 605 606 DEFINE_LOCK_GUARD_1(write_lock, rwlock_t, 607 write_lock(_T->lock), 608 write_unlock(_T->lock)) 609 610 DEFINE_LOCK_GUARD_1(write_lock_irq, rwlock_t, 611 write_lock_irq(_T->lock), 612 write_unlock_irq(_T->lock)) 613 614 DEFINE_LOCK_GUARD_1(write_lock_irqsave, rwlock_t, 615 write_lock_irqsave(_T->lock, _T->flags), 616 write_unlock_irqrestore(_T->lock, _T->flags), 617 unsigned long flags) 618 619 #undef __LINUX_INSIDE_SPINLOCK_H 620 #endif /* __LINUX_SPINLOCK_H */