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_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/kernel.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()        do { } while (0)
 176 #endif
 177
 178 #ifdef CONFIG_DEBUG_SPINLOCK
 179  extern void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock);
 180 #define do_raw_spin_lock_flags(lock, flags) do_raw_spin_lock(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 #ifndef arch_spin_lock_flags
 192 #define arch_spin_lock_flags(lock, flags)       arch_spin_lock(lock)
 193 #endif
 194
 195 static inline void
 196 do_raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long *flags) __acquires(lock)
 197 {
 198         __acquire(lock);
 199         arch_spin_lock_flags(&lock->raw_lock, *flags);
 200         mmiowb_spin_lock();
 201 }
 202
 203 static inline int do_raw_spin_trylock(raw_spinlock_t *lock)
 204 {
 205         int ret = arch_spin_trylock(&(lock)->raw_lock);
 206
 207         if (ret)
 208                 mmiowb_spin_lock();
 209
 210         return ret;
 211 }
 212
 213 static inline void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock)
 214 {
 215         mmiowb_spin_unlock();
 216         arch_spin_unlock(&lock->raw_lock);
 217         __release(lock);
 218 }
 219 #endif
 220
 221 /*
 222  * Define the various spin_lock methods.  Note we define these
 223  * regardless of whether CONFIG_SMP or CONFIG_PREEMPTION are set. The
 224  * various methods are defined as nops in the case they are not
 225  * required.
 226  */
 227 #define raw_spin_trylock(lock)  __cond_lock(lock, _raw_spin_trylock(lock))
 228
 229 #define raw_spin_lock(lock)     _raw_spin_lock(lock)
 230
 231 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 232 # define raw_spin_lock_nested(lock, subclass) \
 233         _raw_spin_lock_nested(lock, subclass)
 234
 235 # define raw_spin_lock_nest_lock(lock, nest_lock)                       \
 236          do {                                                           \
 237                  typecheck(struct lockdep_map *, &(nest_lock)->dep_map);\
 238                  _raw_spin_lock_nest_lock(lock, &(nest_lock)->dep_map); \
 239          } while (0)
 240 #else
 241 /*
 242  * Always evaluate the 'subclass' argument to avoid that the compiler
 243  * warns about set-but-not-used variables when building with
 244  * CONFIG_DEBUG_LOCK_ALLOC=n and with W=1.
 245  */
 246 # define raw_spin_lock_nested(lock, subclass)           \
 247         _raw_spin_lock(((void)(subclass), (lock)))
 248 # define raw_spin_lock_nest_lock(lock, nest_lock)       _raw_spin_lock(lock)
 249 #endif
 250
 251 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
 252
 253 #define raw_spin_lock_irqsave(lock, flags)                      \
 254         do {                                            \
 255                 typecheck(unsigned long, flags);        \
 256                 flags = _raw_spin_lock_irqsave(lock);   \
 257         } while (0)
 258
 259 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 260 #define raw_spin_lock_irqsave_nested(lock, flags, subclass)             \
 261         do {                                                            \
 262                 typecheck(unsigned long, flags);                        \
 263                 flags = _raw_spin_lock_irqsave_nested(lock, subclass);  \
 264         } while (0)
 265 #else
 266 #define raw_spin_lock_irqsave_nested(lock, flags, subclass)             \
 267         do {                                                            \
 268                 typecheck(unsigned long, flags);                        \
 269                 flags = _raw_spin_lock_irqsave(lock);                   \
 270         } while (0)
 271 #endif
 272
 273 #else
 274
 275 #define raw_spin_lock_irqsave(lock, flags)              \
 276         do {                                            \
 277                 typecheck(unsigned long, flags);        \
 278                 _raw_spin_lock_irqsave(lock, flags);    \
 279         } while (0)
 280
 281 #define raw_spin_lock_irqsave_nested(lock, flags, subclass)     \
 282         raw_spin_lock_irqsave(lock, flags)
 283
 284 #endif
 285
 286 #define raw_spin_lock_irq(lock)         _raw_spin_lock_irq(lock)
 287 #define raw_spin_lock_bh(lock)          _raw_spin_lock_bh(lock)
 288 #define raw_spin_unlock(lock)           _raw_spin_unlock(lock)
 289 #define raw_spin_unlock_irq(lock)       _raw_spin_unlock_irq(lock)
 290
 291 #define raw_spin_unlock_irqrestore(lock, flags)         \
 292         do {                                                    \
 293                 typecheck(unsigned long, flags);                \
 294                 _raw_spin_unlock_irqrestore(lock, flags);       \
 295         } while (0)
 296 #define raw_spin_unlock_bh(lock)        _raw_spin_unlock_bh(lock)
 297
 298 #define raw_spin_trylock_bh(lock) \
 299         __cond_lock(lock, _raw_spin_trylock_bh(lock))
 300
 301 #define raw_spin_trylock_irq(lock) \
 302 ({ \
 303         local_irq_disable(); \
 304         raw_spin_trylock(lock) ? \
 305         1 : ({ local_irq_enable(); 0;  }); \
 306 })
 307
 308 #define raw_spin_trylock_irqsave(lock, flags) \
 309 ({ \
 310         local_irq_save(flags); \
 311         raw_spin_trylock(lock) ? \
 312         1 : ({ local_irq_restore(flags); 0; }); \
 313 })
 314
 315 #ifndef CONFIG_PREEMPT_RT
 316 /* Include rwlock functions for !RT */
 317 #include <linux/rwlock.h>
 318 #endif
 319
 320 /*
 321  * Pull the _spin_*()/_read_*()/_write_*() functions/declarations:
 322  */
 323 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
 324 # include <linux/spinlock_api_smp.h>
 325 #else
 326 # include <linux/spinlock_api_up.h>
 327 #endif
 328
 329 /* Non PREEMPT_RT kernel, map to raw spinlocks: */
 330 #ifndef CONFIG_PREEMPT_RT
 331
 332 /*
 333  * Map the spin_lock functions to the raw variants for PREEMPT_RT=n
 334  */
 335
 336 static __always_inline raw_spinlock_t *spinlock_check(spinlock_t *lock)
 337 {
 338         return &lock->rlock;
 339 }
 340
 341 #ifdef CONFIG_DEBUG_SPINLOCK
 342
 343 # define spin_lock_init(lock)                                   \
 344 do {                                                            \
 345         static struct lock_class_key __key;                     \
 346                                                                 \
 347         __raw_spin_lock_init(spinlock_check(lock),              \
 348                              #lock, &__key, LD_WAIT_CONFIG);    \
 349 } while (0)
 350
 351 #else
 352
 353 # define spin_lock_init(_lock)                  \
 354 do {                                            \
 355         spinlock_check(_lock);                  \
 356         *(_lock) = __SPIN_LOCK_UNLOCKED(_lock); \
 357 } while (0)
 358
 359 #endif
 360
 361 static __always_inline void spin_lock(spinlock_t *lock)
 362 {
 363         raw_spin_lock(&lock->rlock);
 364 }
 365
 366 static __always_inline void spin_lock_bh(spinlock_t *lock)
 367 {
 368         raw_spin_lock_bh(&lock->rlock);
 369 }
 370
 371 static __always_inline int spin_trylock(spinlock_t *lock)
 372 {
 373         return raw_spin_trylock(&lock->rlock);
 374 }
 375
 376 #define spin_lock_nested(lock, subclass)                        \
 377 do {                                                            \
 378         raw_spin_lock_nested(spinlock_check(lock), subclass);   \
 379 } while (0)
 380
 381 #define spin_lock_nest_lock(lock, nest_lock)                            \
 382 do {                                                                    \
 383         raw_spin_lock_nest_lock(spinlock_check(lock), nest_lock);       \
 384 } while (0)
 385
 386 static __always_inline void spin_lock_irq(spinlock_t *lock)
 387 {
 388         raw_spin_lock_irq(&lock->rlock);
 389 }
 390
 391 #define spin_lock_irqsave(lock, flags)                          \
 392 do {                                                            \
 393         raw_spin_lock_irqsave(spinlock_check(lock), flags);     \
 394 } while (0)
 395
 396 #define spin_lock_irqsave_nested(lock, flags, subclass)                 \
 397 do {                                                                    \
 398         raw_spin_lock_irqsave_nested(spinlock_check(lock), flags, subclass); \
 399 } while (0)
 400
 401 static __always_inline void spin_unlock(spinlock_t *lock)
 402 {
 403         raw_spin_unlock(&lock->rlock);
 404 }
 405
 406 static __always_inline void spin_unlock_bh(spinlock_t *lock)
 407 {
 408         raw_spin_unlock_bh(&lock->rlock);
 409 }
 410
 411 static __always_inline void spin_unlock_irq(spinlock_t *lock)
 412 {
 413         raw_spin_unlock_irq(&lock->rlock);
 414 }
 415
 416 static __always_inline void spin_unlock_irqrestore(spinlock_t *lock, unsigned long flags)
 417 {
 418         raw_spin_unlock_irqrestore(&lock->rlock, flags);
 419 }
 420
 421 static __always_inline int spin_trylock_bh(spinlock_t *lock)
 422 {
 423         return raw_spin_trylock_bh(&lock->rlock);
 424 }
 425
 426 static __always_inline int spin_trylock_irq(spinlock_t *lock)
 427 {
 428         return raw_spin_trylock_irq(&lock->rlock);
 429 }
 430
 431 #define spin_trylock_irqsave(lock, flags)                       \
 432 ({                                                              \
 433         raw_spin_trylock_irqsave(spinlock_check(lock), flags); \
 434 })
 435
 436 /**
 437  * spin_is_locked() - Check whether a spinlock is locked.
 438  * @lock: Pointer to the spinlock.
 439  *
 440  * This function is NOT required to provide any memory ordering
 441  * guarantees; it could be used for debugging purposes or, when
 442  * additional synchronization is needed, accompanied with other
 443  * constructs (memory barriers) enforcing the synchronization.
 444  *
 445  * Returns: 1 if @lock is locked, 0 otherwise.
 446  *
 447  * Note that the function only tells you that the spinlock is
 448  * seen to be locked, not that it is locked on your CPU.
 449  *
 450  * Further, on CONFIG_SMP=n builds with CONFIG_DEBUG_SPINLOCK=n,
 451  * the return value is always 0 (see include/linux/spinlock_up.h).
 452  * Therefore you should not rely heavily on the return value.
 453  */
 454 static __always_inline int spin_is_locked(spinlock_t *lock)
 455 {
 456         return raw_spin_is_locked(&lock->rlock);
 457 }
 458
 459 static __always_inline int spin_is_contended(spinlock_t *lock)
 460 {
 461         return raw_spin_is_contended(&lock->rlock);
 462 }
 463
 464 #define assert_spin_locked(lock)        assert_raw_spin_locked(&(lock)->rlock)
 465
 466 #else  /* !CONFIG_PREEMPT_RT */
 467 # include <linux/spinlock_rt.h>
 468 #endif /* CONFIG_PREEMPT_RT */
 469
 470 /*
 471  * Pull the atomic_t declaration:
 472  * (asm-mips/atomic.h needs above definitions)
 473  */
 474 #include <linux/atomic.h>
 475 /**
 476  * atomic_dec_and_lock - lock on reaching reference count zero
 477  * @atomic: the atomic counter
 478  * @lock: the spinlock in question
 479  *
 480  * Decrements @atomic by 1.  If the result is 0, returns true and locks
 481  * @lock.  Returns false for all other cases.
 482  */
 483 extern int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock);
 484 #define atomic_dec_and_lock(atomic, lock) \
 485                 __cond_lock(lock, _atomic_dec_and_lock(atomic, lock))
 486
 487 extern int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock,
 488                                         unsigned long *flags);
 489 #define atomic_dec_and_lock_irqsave(atomic, lock, flags) \
 490                 __cond_lock(lock, _atomic_dec_and_lock_irqsave(atomic, lock, &(flags)))
 491
 492 int __alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *lock_mask,
 493                              size_t max_size, unsigned int cpu_mult,
 494                              gfp_t gfp, const char *name,
 495                              struct lock_class_key *key);
 496
 497 #define alloc_bucket_spinlocks(locks, lock_mask, max_size, cpu_mult, gfp)    \
 498         ({                                                                   \
 499                 static struct lock_class_key key;                            \
 500                 int ret;                                                     \
 501                                                                              \
 502                 ret = __alloc_bucket_spinlocks(locks, lock_mask, max_size,   \
 503                                                cpu_mult, gfp, #locks, &key); \
 504                 ret;                                                         \
 505         })
 506
 507 void free_bucket_spinlocks(spinlock_t *locks);
 508
 509 #endif /* __LINUX_SPINLOCK_H */