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 <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 */