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