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
  61
  62 /*
  63  * Must define these before including other files, inline functions need them
  64  */
  65 #define LOCK_SECTION_NAME ".text..lock."KBUILD_BASENAME
  66
  67 #define LOCK_SECTION_START(extra)               \
  68         ".subsection 1\n\t"                     \
  69         extra                                   \
  70         ".ifndef " LOCK_SECTION_NAME "\n\t"     \
  71         LOCK_SECTION_NAME ":\n\t"               \
  72         ".endif\n"
  73
  74 #define LOCK_SECTION_END                        \
  75         ".previous\n\t"
  76
  77 #define __lockfunc __attribute__((section(".spinlock.text")))
  78
  79 /*
  80  * Pull the arch_spinlock_t and arch_rwlock_t definitions:
  81  */
  82 #include <linux/spinlock_types.h>
  83
  84 /*
  85  * Pull the arch_spin*() functions/declarations (UP-nondebug doesn't need them):
  86  */
  87 #ifdef CONFIG_SMP
  88 # include <asm/spinlock.h>
  89 #else
  90 # include <linux/spinlock_up.h>
  91 #endif
  92
  93 #ifdef CONFIG_DEBUG_SPINLOCK
  94   extern void __raw_spin_lock_init(raw_spinlock_t *lock, const char *name,
  95                                    struct lock_class_key *key);
  96 # define raw_spin_lock_init(lock)                               \
  97 do {                                                            \
  98         static struct lock_class_key __key;                     \
  99                                                                 \
 100         __raw_spin_lock_init((lock), #lock, &__key);            \
 101 } while (0)
 102
 103 #else
 104 # define raw_spin_lock_init(lock)                               \
 105         do { *(lock) = __RAW_SPIN_LOCK_UNLOCKED(lock); } while (0)
 106 #endif
 107
 108 #define raw_spin_is_locked(lock)        arch_spin_is_locked(&(lock)->raw_lock)
 109
 110 #ifdef arch_spin_is_contended
 111 #define raw_spin_is_contended(lock)     arch_spin_is_contended(&(lock)->raw_lock)
 112 #else
 113 #define raw_spin_is_contended(lock)     (((void)(lock), 0))
 114 #endif /*arch_spin_is_contended*/
 115
 116 /*
 117  * smp_mb__after_spinlock() provides the equivalent of a full memory barrier
 118  * between program-order earlier lock acquisitions and program-order later
 119  * memory accesses.
 120  *
 121  * This guarantees that the following two properties hold:
 122  *
 123  *   1) Given the snippet:
 124  *
 125  *        { X = 0;  Y = 0; }
 126  *
 127  *        CPU0                          CPU1
 128  *
 129  *        WRITE_ONCE(X, 1);             WRITE_ONCE(Y, 1);
 130  *        spin_lock(S);                 smp_mb();
 131  *        smp_mb__after_spinlock();     r1 = READ_ONCE(X);
 132  *        r0 = READ_ONCE(Y);
 133  *        spin_unlock(S);
 134  *
 135  *      it is forbidden that CPU0 does not observe CPU1's store to Y (r0 = 0)
 136  *      and CPU1 does not observe CPU0's store to X (r1 = 0); see the comments
 137  *      preceding the call to smp_mb__after_spinlock() in __schedule() and in
 138  *      try_to_wake_up().
 139  *
 140  *   2) Given the snippet:
 141  *
 142  *  { X = 0;  Y = 0; }
 143  *
 144  *  CPU0                CPU1                            CPU2
 145  *
 146  *  spin_lock(S);       spin_lock(S);                   r1 = READ_ONCE(Y);
 147  *  WRITE_ONCE(X, 1);   smp_mb__after_spinlock();       smp_rmb();
 148  *  spin_unlock(S);     r0 = READ_ONCE(X);              r2 = READ_ONCE(X);
 149  *                      WRITE_ONCE(Y, 1);
 150  *                      spin_unlock(S);
 151  *
 152  *      it is forbidden that CPU0's critical section executes before CPU1's
 153  *      critical section (r0 = 1), CPU2 observes CPU1's store to Y (r1 = 1)
 154  *      and CPU2 does not observe CPU0's store to X (r2 = 0); see the comments
 155  *      preceding the calls to smp_rmb() in try_to_wake_up() for similar
 156  *      snippets but "projected" onto two CPUs.
 157  *
 158  * Property (2) upgrades the lock to an RCsc lock.
 159  *
 160  * Since most load-store architectures implement ACQUIRE with an smp_mb() after
 161  * the LL/SC loop, they need no further barriers. Similarly all our TSO
 162  * architectures imply an smp_mb() for each atomic instruction and equally don't
 163  * need more.
 164  *
 165  * Architectures that can implement ACQUIRE better need to take care.
 166  */
 167 #ifndef smp_mb__after_spinlock
 168 #define smp_mb__after_spinlock()        do { } while (0)
 169 #endif
 170
 171 #ifdef CONFIG_DEBUG_SPINLOCK
 172  extern void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock);
 173 #define do_raw_spin_lock_flags(lock, flags) do_raw_spin_lock(lock)
 174  extern int do_raw_spin_trylock(raw_spinlock_t *lock);
 175  extern void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock);
 176 #else
 177 static inline void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock)
 178 {
 179         __acquire(lock);
 180         arch_spin_lock(&lock->raw_lock);
 181 }
 182
 183 #ifndef arch_spin_lock_flags
 184 #define arch_spin_lock_flags(lock, flags)       arch_spin_lock(lock)
 185 #endif
 186
 187 static inline void
 188 do_raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long *flags) __acquires(lock)
 189 {
 190         __acquire(lock);
 191         arch_spin_lock_flags(&lock->raw_lock, *flags);
 192 }
 193
 194 static inline int do_raw_spin_trylock(raw_spinlock_t *lock)
 195 {
 196         return arch_spin_trylock(&(lock)->raw_lock);
 197 }
 198
 199 static inline void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock)
 200 {
 201         arch_spin_unlock(&lock->raw_lock);
 202         __release(lock);
 203 }
 204 #endif
 205
 206 /*
 207  * Define the various spin_lock methods.  Note we define these
 208  * regardless of whether CONFIG_SMP or CONFIG_PREEMPT are set. The
 209  * various methods are defined as nops in the case they are not
 210  * required.
 211  */
 212 #define raw_spin_trylock(lock)  __cond_lock(lock, _raw_spin_trylock(lock))
 213
 214 #define raw_spin_lock(lock)     _raw_spin_lock(lock)
 215
 216 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 217 # define raw_spin_lock_nested(lock, subclass) \
 218         _raw_spin_lock_nested(lock, subclass)
 219
 220 # define raw_spin_lock_nest_lock(lock, nest_lock)                       \
 221          do {                                                           \
 222                  typecheck(struct lockdep_map *, &(nest_lock)->dep_map);\
 223                  _raw_spin_lock_nest_lock(lock, &(nest_lock)->dep_map); \
 224          } while (0)
 225 #else
 226 /*
 227  * Always evaluate the 'subclass' argument to avoid that the compiler
 228  * warns about set-but-not-used variables when building with
 229  * CONFIG_DEBUG_LOCK_ALLOC=n and with W=1.
 230  */
 231 # define raw_spin_lock_nested(lock, subclass)           \
 232         _raw_spin_lock(((void)(subclass), (lock)))
 233 # define raw_spin_lock_nest_lock(lock, nest_lock)       _raw_spin_lock(lock)
 234 #endif
 235
 236 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
 237
 238 #define raw_spin_lock_irqsave(lock, flags)                      \
 239         do {                                            \
 240                 typecheck(unsigned long, flags);        \
 241                 flags = _raw_spin_lock_irqsave(lock);   \
 242         } while (0)
 243
 244 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 245 #define raw_spin_lock_irqsave_nested(lock, flags, subclass)             \
 246         do {                                                            \
 247                 typecheck(unsigned long, flags);                        \
 248                 flags = _raw_spin_lock_irqsave_nested(lock, subclass);  \
 249         } while (0)
 250 #else
 251 #define raw_spin_lock_irqsave_nested(lock, flags, subclass)             \
 252         do {                                                            \
 253                 typecheck(unsigned long, flags);                        \
 254                 flags = _raw_spin_lock_irqsave(lock);                   \
 255         } while (0)
 256 #endif
 257
 258 #else
 259
 260 #define raw_spin_lock_irqsave(lock, flags)              \
 261         do {                                            \
 262                 typecheck(unsigned long, flags);        \
 263                 _raw_spin_lock_irqsave(lock, flags);    \
 264         } while (0)
 265
 266 #define raw_spin_lock_irqsave_nested(lock, flags, subclass)     \
 267         raw_spin_lock_irqsave(lock, flags)
 268
 269 #endif
 270
 271 #define raw_spin_lock_irq(lock)         _raw_spin_lock_irq(lock)
 272 #define raw_spin_lock_bh(lock)          _raw_spin_lock_bh(lock)
 273 #define raw_spin_unlock(lock)           _raw_spin_unlock(lock)
 274 #define raw_spin_unlock_irq(lock)       _raw_spin_unlock_irq(lock)
 275
 276 #define raw_spin_unlock_irqrestore(lock, flags)         \
 277         do {                                                    \
 278                 typecheck(unsigned long, flags);                \
 279                 _raw_spin_unlock_irqrestore(lock, flags);       \
 280         } while (0)
 281 #define raw_spin_unlock_bh(lock)        _raw_spin_unlock_bh(lock)
 282
 283 #define raw_spin_trylock_bh(lock) \
 284         __cond_lock(lock, _raw_spin_trylock_bh(lock))
 285
 286 #define raw_spin_trylock_irq(lock) \
 287 ({ \
 288         local_irq_disable(); \
 289         raw_spin_trylock(lock) ? \
 290         1 : ({ local_irq_enable(); 0;  }); \
 291 })
 292
 293 #define raw_spin_trylock_irqsave(lock, flags) \
 294 ({ \
 295         local_irq_save(flags); \
 296         raw_spin_trylock(lock) ? \
 297         1 : ({ local_irq_restore(flags); 0; }); \
 298 })
 299
 300 /* Include rwlock functions */
 301 #include <linux/rwlock.h>
 302
 303 /*
 304  * Pull the _spin_*()/_read_*()/_write_*() functions/declarations:
 305  */
 306 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
 307 # include <linux/spinlock_api_smp.h>
 308 #else
 309 # include <linux/spinlock_api_up.h>
 310 #endif
 311
 312 /*
 313  * Map the spin_lock functions to the raw variants for PREEMPT_RT=n
 314  */
 315
 316 static __always_inline raw_spinlock_t *spinlock_check(spinlock_t *lock)
 317 {
 318         return &lock->rlock;
 319 }
 320
 321 #define spin_lock_init(_lock)                           \
 322 do {                                                    \
 323         spinlock_check(_lock);                          \
 324         raw_spin_lock_init(&(_lock)->rlock);            \
 325 } while (0)
 326
 327 static __always_inline void spin_lock(spinlock_t *lock)
 328 {
 329         raw_spin_lock(&lock->rlock);
 330 }
 331
 332 static __always_inline void spin_lock_bh(spinlock_t *lock)
 333 {
 334         raw_spin_lock_bh(&lock->rlock);
 335 }
 336
 337 static __always_inline int spin_trylock(spinlock_t *lock)
 338 {
 339         return raw_spin_trylock(&lock->rlock);
 340 }
 341
 342 #define spin_lock_nested(lock, subclass)                        \
 343 do {                                                            \
 344         raw_spin_lock_nested(spinlock_check(lock), subclass);   \
 345 } while (0)
 346
 347 #define spin_lock_nest_lock(lock, nest_lock)                            \
 348 do {                                                                    \
 349         raw_spin_lock_nest_lock(spinlock_check(lock), nest_lock);       \
 350 } while (0)
 351
 352 static __always_inline void spin_lock_irq(spinlock_t *lock)
 353 {
 354         raw_spin_lock_irq(&lock->rlock);
 355 }
 356
 357 #define spin_lock_irqsave(lock, flags)                          \
 358 do {                                                            \
 359         raw_spin_lock_irqsave(spinlock_check(lock), flags);     \
 360 } while (0)
 361
 362 #define spin_lock_irqsave_nested(lock, flags, subclass)                 \
 363 do {                                                                    \
 364         raw_spin_lock_irqsave_nested(spinlock_check(lock), flags, subclass); \
 365 } while (0)
 366
 367 static __always_inline void spin_unlock(spinlock_t *lock)
 368 {
 369         raw_spin_unlock(&lock->rlock);
 370 }
 371
 372 static __always_inline void spin_unlock_bh(spinlock_t *lock)
 373 {
 374         raw_spin_unlock_bh(&lock->rlock);
 375 }
 376
 377 static __always_inline void spin_unlock_irq(spinlock_t *lock)
 378 {
 379         raw_spin_unlock_irq(&lock->rlock);
 380 }
 381
 382 static __always_inline void spin_unlock_irqrestore(spinlock_t *lock, unsigned long flags)
 383 {
 384         raw_spin_unlock_irqrestore(&lock->rlock, flags);
 385 }
 386
 387 static __always_inline int spin_trylock_bh(spinlock_t *lock)
 388 {
 389         return raw_spin_trylock_bh(&lock->rlock);
 390 }
 391
 392 static __always_inline int spin_trylock_irq(spinlock_t *lock)
 393 {
 394         return raw_spin_trylock_irq(&lock->rlock);
 395 }
 396
 397 #define spin_trylock_irqsave(lock, flags)                       \
 398 ({                                                              \
 399         raw_spin_trylock_irqsave(spinlock_check(lock), flags); \
 400 })
 401
 402 /**
 403  * spin_is_locked() - Check whether a spinlock is locked.
 404  * @lock: Pointer to the spinlock.
 405  *
 406  * This function is NOT required to provide any memory ordering
 407  * guarantees; it could be used for debugging purposes or, when
 408  * additional synchronization is needed, accompanied with other
 409  * constructs (memory barriers) enforcing the synchronization.
 410  *
 411  * Returns: 1 if @lock is locked, 0 otherwise.
 412  *
 413  * Note that the function only tells you that the spinlock is
 414  * seen to be locked, not that it is locked on your CPU.
 415  *
 416  * Further, on CONFIG_SMP=n builds with CONFIG_DEBUG_SPINLOCK=n,
 417  * the return value is always 0 (see include/linux/spinlock_up.h).
 418  * Therefore you should not rely heavily on the return value.
 419  */
 420 static __always_inline int spin_is_locked(spinlock_t *lock)
 421 {
 422         return raw_spin_is_locked(&lock->rlock);
 423 }
 424
 425 static __always_inline int spin_is_contended(spinlock_t *lock)
 426 {
 427         return raw_spin_is_contended(&lock->rlock);
 428 }
 429
 430 #define assert_spin_locked(lock)        assert_raw_spin_locked(&(lock)->rlock)
 431
 432 /*
 433  * Pull the atomic_t declaration:
 434  * (asm-mips/atomic.h needs above definitions)
 435  */
 436 #include <linux/atomic.h>
 437 /**
 438  * atomic_dec_and_lock - lock on reaching reference count zero
 439  * @atomic: the atomic counter
 440  * @lock: the spinlock in question
 441  *
 442  * Decrements @atomic by 1.  If the result is 0, returns true and locks
 443  * @lock.  Returns false for all other cases.
 444  */
 445 extern int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock);
 446 #define atomic_dec_and_lock(atomic, lock) \
 447                 __cond_lock(lock, _atomic_dec_and_lock(atomic, lock))
 448
 449 extern int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock,
 450                                         unsigned long *flags);
 451 #define atomic_dec_and_lock_irqsave(atomic, lock, flags) \
 452                 __cond_lock(lock, _atomic_dec_and_lock_irqsave(atomic, lock, &(flags)))
 453
 454 int __alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *lock_mask,
 455                              size_t max_size, unsigned int cpu_mult,
 456                              gfp_t gfp, const char *name,
 457                              struct lock_class_key *key);
 458
 459 #define alloc_bucket_spinlocks(locks, lock_mask, max_size, cpu_mult, gfp)    \
 460         ({                                                                   \
 461                 static struct lock_class_key key;                            \
 462                 int ret;                                                     \
 463                                                                              \
 464                 ret = __alloc_bucket_spinlocks(locks, lock_mask, max_size,   \
 465                                                cpu_mult, gfp, #locks, &key); \
 466                 ret;                                                         \
 467         })
 468
 469 void free_bucket_spinlocks(spinlock_t *locks);
 470
 471 #endif /* __LINUX_SPINLOCK_H */