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  * Pull the atomic_t declaration:
 460  * (asm-mips/atomic.h needs above definitions)
 461  */
 462 #include <linux/atomic.h>
 463 /**
 464  * atomic_dec_and_lock - lock on reaching reference count zero
 465  * @atomic: the atomic counter
 466  * @lock: the spinlock in question
 467  *
 468  * Decrements @atomic by 1.  If the result is 0, returns true and locks
 469  * @lock.  Returns false for all other cases.
 470  */
 471 extern int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock);
 472 #define atomic_dec_and_lock(atomic, lock) \
 473                 __cond_lock(lock, _atomic_dec_and_lock(atomic, lock))
 474
 475 extern int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock,
 476                                         unsigned long *flags);
 477 #define atomic_dec_and_lock_irqsave(atomic, lock, flags) \
 478                 __cond_lock(lock, _atomic_dec_and_lock_irqsave(atomic, lock, &(flags)))
 479
 480 extern int _atomic_dec_and_raw_lock(atomic_t *atomic, raw_spinlock_t *lock);
 481 #define atomic_dec_and_raw_lock(atomic, lock) \
 482                 __cond_lock(lock, _atomic_dec_and_raw_lock(atomic, lock))
 483
 484 extern int _atomic_dec_and_raw_lock_irqsave(atomic_t *atomic, raw_spinlock_t *lock,
 485                                         unsigned long *flags);
 486 #define atomic_dec_and_raw_lock_irqsave(atomic, lock, flags) \
 487                 __cond_lock(lock, _atomic_dec_and_raw_lock_irqsave(atomic, lock, &(flags)))
 488
 489 int __alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *lock_mask,
 490                              size_t max_size, unsigned int cpu_mult,
 491                              gfp_t gfp, const char *name,
 492                              struct lock_class_key *key);
 493
 494 #define alloc_bucket_spinlocks(locks, lock_mask, max_size, cpu_mult, gfp)    \
 495         ({                                                                   \
 496                 static struct lock_class_key key;                            \
 497                 int ret;                                                     \
 498                                                                              \
 499                 ret = __alloc_bucket_spinlocks(locks, lock_mask, max_size,   \
 500                                                cpu_mult, gfp, #locks, &key); \
 501                 ret;                                                         \
 502         })
 503
 504 void free_bucket_spinlocks(spinlock_t *locks);
 505
 506 DEFINE_LOCK_GUARD_1(raw_spinlock, raw_spinlock_t,
 507                     raw_spin_lock(_T->lock),
 508                     raw_spin_unlock(_T->lock))
 509
 510 DEFINE_LOCK_GUARD_1(raw_spinlock_nested, raw_spinlock_t,
 511                     raw_spin_lock_nested(_T->lock, SINGLE_DEPTH_NESTING),
 512                     raw_spin_unlock(_T->lock))
 513
 514 DEFINE_LOCK_GUARD_1(raw_spinlock_irq, raw_spinlock_t,
 515                     raw_spin_lock_irq(_T->lock),
 516                     raw_spin_unlock_irq(_T->lock))
 517
 518 DEFINE_LOCK_GUARD_1(raw_spinlock_irqsave, raw_spinlock_t,
 519                     raw_spin_lock_irqsave(_T->lock, _T->flags),
 520                     raw_spin_unlock_irqrestore(_T->lock, _T->flags),
 521                     unsigned long flags)
 522
 523 DEFINE_LOCK_GUARD_1(spinlock, spinlock_t,
 524                     spin_lock(_T->lock),
 525                     spin_unlock(_T->lock))
 526
 527 DEFINE_LOCK_GUARD_1(spinlock_irq, spinlock_t,
 528                     spin_lock_irq(_T->lock),
 529                     spin_unlock_irq(_T->lock))
 530
 531 DEFINE_LOCK_GUARD_1(spinlock_irqsave, spinlock_t,
 532                     spin_lock_irqsave(_T->lock, _T->flags),
 533                     spin_unlock_irqrestore(_T->lock, _T->flags),
 534                     unsigned long flags)
 535
 536 #undef __LINUX_INSIDE_SPINLOCK_H
 537 #endif /* __LINUX_SPINLOCK_H */