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 <asm/barrier.h> 65 #include <asm/mmiowb.h> 66 67 68 /* 69 * Must define these before including other files, inline functions need them 70 */ 71 #define LOCK_SECTION_NAME ".text..lock."KBUILD_BASENAME 72 73 #define LOCK_SECTION_START(extra) \ 74 ".subsection 1\n\t" \ 75 extra \ 76 ".ifndef " LOCK_SECTION_NAME "\n\t" \ 77 LOCK_SECTION_NAME ":\n\t" \ 78 ".endif\n" 79 80 #define LOCK_SECTION_END \ 81 ".previous\n\t" 82 83 #define __lockfunc __section(".spinlock.text") 84 85 /* 86 * Pull the arch_spinlock_t and arch_rwlock_t definitions: 87 */ 88 #include <linux/spinlock_types.h> 89 90 /* 91 * Pull the arch_spin*() functions/declarations (UP-nondebug doesn't need them): 92 */ 93 #ifdef CONFIG_SMP 94 # include <asm/spinlock.h> 95 #else 96 # include <linux/spinlock_up.h> 97 #endif 98 99 #ifdef CONFIG_DEBUG_SPINLOCK 100 extern void __raw_spin_lock_init(raw_spinlock_t *lock, const char *name, 101 struct lock_class_key *key, short inner); 102 103 # define raw_spin_lock_init(lock) \ 104 do { \ 105 static struct lock_class_key __key; \ 106 \ 107 __raw_spin_lock_init((lock), #lock, &__key, LD_WAIT_SPIN); \ 108 } while (0) 109 110 #else 111 # define raw_spin_lock_init(lock) \ 112 do { *(lock) = __RAW_SPIN_LOCK_UNLOCKED(lock); } while (0) 113 #endif 114 115 #define raw_spin_is_locked(lock) arch_spin_is_locked(&(lock)->raw_lock) 116 117 #ifdef arch_spin_is_contended 118 #define raw_spin_is_contended(lock) arch_spin_is_contended(&(lock)->raw_lock) 119 #else 120 #define raw_spin_is_contended(lock) (((void)(lock), 0)) 121 #endif /*arch_spin_is_contended*/ 122 123 /* 124 * smp_mb__after_spinlock() provides the equivalent of a full memory barrier 125 * between program-order earlier lock acquisitions and program-order later 126 * memory accesses. 127 * 128 * This guarantees that the following two properties hold: 129 * 130 * 1) Given the snippet: 131 * 132 * { X = 0; Y = 0; } 133 * 134 * CPU0 CPU1 135 * 136 * WRITE_ONCE(X, 1); WRITE_ONCE(Y, 1); 137 * spin_lock(S); smp_mb(); 138 * smp_mb__after_spinlock(); r1 = READ_ONCE(X); 139 * r0 = READ_ONCE(Y); 140 * spin_unlock(S); 141 * 142 * it is forbidden that CPU0 does not observe CPU1's store to Y (r0 = 0) 143 * and CPU1 does not observe CPU0's store to X (r1 = 0); see the comments 144 * preceding the call to smp_mb__after_spinlock() in __schedule() and in 145 * try_to_wake_up(). 146 * 147 * 2) Given the snippet: 148 * 149 * { X = 0; Y = 0; } 150 * 151 * CPU0 CPU1 CPU2 152 * 153 * spin_lock(S); spin_lock(S); r1 = READ_ONCE(Y); 154 * WRITE_ONCE(X, 1); smp_mb__after_spinlock(); smp_rmb(); 155 * spin_unlock(S); r0 = READ_ONCE(X); r2 = READ_ONCE(X); 156 * WRITE_ONCE(Y, 1); 157 * spin_unlock(S); 158 * 159 * it is forbidden that CPU0's critical section executes before CPU1's 160 * critical section (r0 = 1), CPU2 observes CPU1's store to Y (r1 = 1) 161 * and CPU2 does not observe CPU0's store to X (r2 = 0); see the comments 162 * preceding the calls to smp_rmb() in try_to_wake_up() for similar 163 * snippets but "projected" onto two CPUs. 164 * 165 * Property (2) upgrades the lock to an RCsc lock. 166 * 167 * Since most load-store architectures implement ACQUIRE with an smp_mb() after 168 * the LL/SC loop, they need no further barriers. Similarly all our TSO 169 * architectures imply an smp_mb() for each atomic instruction and equally don't 170 * need more. 171 * 172 * Architectures that can implement ACQUIRE better need to take care. 173 */ 174 #ifndef smp_mb__after_spinlock 175 #define smp_mb__after_spinlock() kcsan_mb() 176 #endif 177 178 #ifdef CONFIG_DEBUG_SPINLOCK 179 extern void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock); 180 extern int do_raw_spin_trylock(raw_spinlock_t *lock); 181 extern void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock); 182 #else 183 static inline void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock) 184 { 185 __acquire(lock); 186 arch_spin_lock(&lock->raw_lock); 187 mmiowb_spin_lock(); 188 } 189 190 static inline int do_raw_spin_trylock(raw_spinlock_t *lock) 191 { 192 int ret = arch_spin_trylock(&(lock)->raw_lock); 193 194 if (ret) 195 mmiowb_spin_lock(); 196 197 return ret; 198 } 199 200 static inline void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock) 201 { 202 mmiowb_spin_unlock(); 203 arch_spin_unlock(&lock->raw_lock); 204 __release(lock); 205 } 206 #endif 207 208 /* 209 * Define the various spin_lock methods. Note we define these 210 * regardless of whether CONFIG_SMP or CONFIG_PREEMPTION are set. The 211 * various methods are defined as nops in the case they are not 212 * required. 213 */ 214 #define raw_spin_trylock(lock) __cond_lock(lock, _raw_spin_trylock(lock)) 215 216 #define raw_spin_lock(lock) _raw_spin_lock(lock) 217 218 #ifdef CONFIG_DEBUG_LOCK_ALLOC 219 # define raw_spin_lock_nested(lock, subclass) \ 220 _raw_spin_lock_nested(lock, subclass) 221 222 # define raw_spin_lock_nest_lock(lock, nest_lock) \ 223 do { \ 224 typecheck(struct lockdep_map *, &(nest_lock)->dep_map);\ 225 _raw_spin_lock_nest_lock(lock, &(nest_lock)->dep_map); \ 226 } while (0) 227 #else 228 /* 229 * Always evaluate the 'subclass' argument to avoid that the compiler 230 * warns about set-but-not-used variables when building with 231 * CONFIG_DEBUG_LOCK_ALLOC=n and with W=1. 232 */ 233 # define raw_spin_lock_nested(lock, subclass) \ 234 _raw_spin_lock(((void)(subclass), (lock))) 235 # define raw_spin_lock_nest_lock(lock, nest_lock) _raw_spin_lock(lock) 236 #endif 237 238 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) 239 240 #define raw_spin_lock_irqsave(lock, flags) \ 241 do { \ 242 typecheck(unsigned long, flags); \ 243 flags = _raw_spin_lock_irqsave(lock); \ 244 } while (0) 245 246 #ifdef CONFIG_DEBUG_LOCK_ALLOC 247 #define raw_spin_lock_irqsave_nested(lock, flags, subclass) \ 248 do { \ 249 typecheck(unsigned long, flags); \ 250 flags = _raw_spin_lock_irqsave_nested(lock, subclass); \ 251 } while (0) 252 #else 253 #define raw_spin_lock_irqsave_nested(lock, flags, subclass) \ 254 do { \ 255 typecheck(unsigned long, flags); \ 256 flags = _raw_spin_lock_irqsave(lock); \ 257 } while (0) 258 #endif 259 260 #else 261 262 #define raw_spin_lock_irqsave(lock, flags) \ 263 do { \ 264 typecheck(unsigned long, flags); \ 265 _raw_spin_lock_irqsave(lock, flags); \ 266 } while (0) 267 268 #define raw_spin_lock_irqsave_nested(lock, flags, subclass) \ 269 raw_spin_lock_irqsave(lock, flags) 270 271 #endif 272 273 #define raw_spin_lock_irq(lock) _raw_spin_lock_irq(lock) 274 #define raw_spin_lock_bh(lock) _raw_spin_lock_bh(lock) 275 #define raw_spin_unlock(lock) _raw_spin_unlock(lock) 276 #define raw_spin_unlock_irq(lock) _raw_spin_unlock_irq(lock) 277 278 #define raw_spin_unlock_irqrestore(lock, flags) \ 279 do { \ 280 typecheck(unsigned long, flags); \ 281 _raw_spin_unlock_irqrestore(lock, flags); \ 282 } while (0) 283 #define raw_spin_unlock_bh(lock) _raw_spin_unlock_bh(lock) 284 285 #define raw_spin_trylock_bh(lock) \ 286 __cond_lock(lock, _raw_spin_trylock_bh(lock)) 287 288 #define raw_spin_trylock_irq(lock) \ 289 ({ \ 290 local_irq_disable(); \ 291 raw_spin_trylock(lock) ? \ 292 1 : ({ local_irq_enable(); 0; }); \ 293 }) 294 295 #define raw_spin_trylock_irqsave(lock, flags) \ 296 ({ \ 297 local_irq_save(flags); \ 298 raw_spin_trylock(lock) ? \ 299 1 : ({ local_irq_restore(flags); 0; }); \ 300 }) 301 302 #ifndef CONFIG_PREEMPT_RT 303 /* Include rwlock functions for !RT */ 304 #include <linux/rwlock.h> 305 #endif 306 307 /* 308 * Pull the _spin_*()/_read_*()/_write_*() functions/declarations: 309 */ 310 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) 311 # include <linux/spinlock_api_smp.h> 312 #else 313 # include <linux/spinlock_api_up.h> 314 #endif 315 316 /* Non PREEMPT_RT kernel, map to raw spinlocks: */ 317 #ifndef CONFIG_PREEMPT_RT 318 319 /* 320 * Map the spin_lock functions to the raw variants for PREEMPT_RT=n 321 */ 322 323 static __always_inline raw_spinlock_t *spinlock_check(spinlock_t *lock) 324 { 325 return &lock->rlock; 326 } 327 328 #ifdef CONFIG_DEBUG_SPINLOCK 329 330 # define spin_lock_init(lock) \ 331 do { \ 332 static struct lock_class_key __key; \ 333 \ 334 __raw_spin_lock_init(spinlock_check(lock), \ 335 #lock, &__key, LD_WAIT_CONFIG); \ 336 } while (0) 337 338 #else 339 340 # define spin_lock_init(_lock) \ 341 do { \ 342 spinlock_check(_lock); \ 343 *(_lock) = __SPIN_LOCK_UNLOCKED(_lock); \ 344 } while (0) 345 346 #endif 347 348 static __always_inline void spin_lock(spinlock_t *lock) 349 { 350 raw_spin_lock(&lock->rlock); 351 } 352 353 static __always_inline void spin_lock_bh(spinlock_t *lock) 354 { 355 raw_spin_lock_bh(&lock->rlock); 356 } 357 358 static __always_inline int spin_trylock(spinlock_t *lock) 359 { 360 return raw_spin_trylock(&lock->rlock); 361 } 362 363 #define spin_lock_nested(lock, subclass) \ 364 do { \ 365 raw_spin_lock_nested(spinlock_check(lock), subclass); \ 366 } while (0) 367 368 #define spin_lock_nest_lock(lock, nest_lock) \ 369 do { \ 370 raw_spin_lock_nest_lock(spinlock_check(lock), nest_lock); \ 371 } while (0) 372 373 static __always_inline void spin_lock_irq(spinlock_t *lock) 374 { 375 raw_spin_lock_irq(&lock->rlock); 376 } 377 378 #define spin_lock_irqsave(lock, flags) \ 379 do { \ 380 raw_spin_lock_irqsave(spinlock_check(lock), flags); \ 381 } while (0) 382 383 #define spin_lock_irqsave_nested(lock, flags, subclass) \ 384 do { \ 385 raw_spin_lock_irqsave_nested(spinlock_check(lock), flags, subclass); \ 386 } while (0) 387 388 static __always_inline void spin_unlock(spinlock_t *lock) 389 { 390 raw_spin_unlock(&lock->rlock); 391 } 392 393 static __always_inline void spin_unlock_bh(spinlock_t *lock) 394 { 395 raw_spin_unlock_bh(&lock->rlock); 396 } 397 398 static __always_inline void spin_unlock_irq(spinlock_t *lock) 399 { 400 raw_spin_unlock_irq(&lock->rlock); 401 } 402 403 static __always_inline void spin_unlock_irqrestore(spinlock_t *lock, unsigned long flags) 404 { 405 raw_spin_unlock_irqrestore(&lock->rlock, flags); 406 } 407 408 static __always_inline int spin_trylock_bh(spinlock_t *lock) 409 { 410 return raw_spin_trylock_bh(&lock->rlock); 411 } 412 413 static __always_inline int spin_trylock_irq(spinlock_t *lock) 414 { 415 return raw_spin_trylock_irq(&lock->rlock); 416 } 417 418 #define spin_trylock_irqsave(lock, flags) \ 419 ({ \ 420 raw_spin_trylock_irqsave(spinlock_check(lock), flags); \ 421 }) 422 423 /** 424 * spin_is_locked() - Check whether a spinlock is locked. 425 * @lock: Pointer to the spinlock. 426 * 427 * This function is NOT required to provide any memory ordering 428 * guarantees; it could be used for debugging purposes or, when 429 * additional synchronization is needed, accompanied with other 430 * constructs (memory barriers) enforcing the synchronization. 431 * 432 * Returns: 1 if @lock is locked, 0 otherwise. 433 * 434 * Note that the function only tells you that the spinlock is 435 * seen to be locked, not that it is locked on your CPU. 436 * 437 * Further, on CONFIG_SMP=n builds with CONFIG_DEBUG_SPINLOCK=n, 438 * the return value is always 0 (see include/linux/spinlock_up.h). 439 * Therefore you should not rely heavily on the return value. 440 */ 441 static __always_inline int spin_is_locked(spinlock_t *lock) 442 { 443 return raw_spin_is_locked(&lock->rlock); 444 } 445 446 static __always_inline int spin_is_contended(spinlock_t *lock) 447 { 448 return raw_spin_is_contended(&lock->rlock); 449 } 450 451 #define assert_spin_locked(lock) assert_raw_spin_locked(&(lock)->rlock) 452 453 #else /* !CONFIG_PREEMPT_RT */ 454 # include <linux/spinlock_rt.h> 455 #endif /* CONFIG_PREEMPT_RT */ 456 457 /* 458 * Pull the atomic_t declaration: 459 * (asm-mips/atomic.h needs above definitions) 460 */ 461 #include <linux/atomic.h> 462 /** 463 * atomic_dec_and_lock - lock on reaching reference count zero 464 * @atomic: the atomic counter 465 * @lock: the spinlock in question 466 * 467 * Decrements @atomic by 1. If the result is 0, returns true and locks 468 * @lock. Returns false for all other cases. 469 */ 470 extern int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock); 471 #define atomic_dec_and_lock(atomic, lock) \ 472 __cond_lock(lock, _atomic_dec_and_lock(atomic, lock)) 473 474 extern int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock, 475 unsigned long *flags); 476 #define atomic_dec_and_lock_irqsave(atomic, lock, flags) \ 477 __cond_lock(lock, _atomic_dec_and_lock_irqsave(atomic, lock, &(flags))) 478 479 int __alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *lock_mask, 480 size_t max_size, unsigned int cpu_mult, 481 gfp_t gfp, const char *name, 482 struct lock_class_key *key); 483 484 #define alloc_bucket_spinlocks(locks, lock_mask, max_size, cpu_mult, gfp) \ 485 ({ \ 486 static struct lock_class_key key; \ 487 int ret; \ 488 \ 489 ret = __alloc_bucket_spinlocks(locks, lock_mask, max_size, \ 490 cpu_mult, gfp, #locks, &key); \ 491 ret; \ 492 }) 493 494 void free_bucket_spinlocks(spinlock_t *locks); 495 496 #undef __LINUX_INSIDE_SPINLOCK_H 497 #endif /* __LINUX_SPINLOCK_H */ 498