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