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