include/linux/spinlock.h

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