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