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);
  97 # define raw_spin_lock_init(lock)                               \
  98 do {                                                            \
  99         static struct lock_class_key __key;                     \
 100                                                                 \
 101         __raw_spin_lock_init((lock), #lock, &__key);            \
 102 } while (0)
 103
 104 #else
 105 # define raw_spin_lock_init(lock)                               \
 106         do { *(lock) = __RAW_SPIN_LOCK_UNLOCKED(lock); } while (0)
 107 #endif
 108
 109 #define raw_spin_is_locked(lock)        arch_spin_is_locked(&(lock)->raw_lock)
 110
 111 #ifdef arch_spin_is_contended
 112 #define raw_spin_is_contended(lock)     arch_spin_is_contended(&(lock)->raw_lock)
 113 #else
 114 #define raw_spin_is_contended(lock)     (((void)(lock), 0))
 115 #endif /*arch_spin_is_contended*/
 116
 117 /*
 118  * smp_mb__after_spinlock() provides the equivalent of a full memory barrier
 119  * between program-order earlier lock acquisitions and program-order later
 120  * memory accesses.
 121  *
 122  * This guarantees that the following two properties hold:
 123  *
 124  *   1) Given the snippet:
 125  *
 126  *        { X = 0;  Y = 0; }
 127  *
 128  *        CPU0                          CPU1
 129  *
 130  *        WRITE_ONCE(X, 1);             WRITE_ONCE(Y, 1);
 131  *        spin_lock(S);                 smp_mb();
 132  *        smp_mb__after_spinlock();     r1 = READ_ONCE(X);
 133  *        r0 = READ_ONCE(Y);
 134  *        spin_unlock(S);
 135  *
 136  *      it is forbidden that CPU0 does not observe CPU1's store to Y (r0 = 0)
 137  *      and CPU1 does not observe CPU0's store to X (r1 = 0); see the comments
 138  *      preceding the call to smp_mb__after_spinlock() in __schedule() and in
 139  *      try_to_wake_up().
 140  *
 141  *   2) Given the snippet:
 142  *
 143  *  { X = 0;  Y = 0; }
 144  *
 145  *  CPU0                CPU1                            CPU2
 146  *
 147  *  spin_lock(S);       spin_lock(S);                   r1 = READ_ONCE(Y);
 148  *  WRITE_ONCE(X, 1);   smp_mb__after_spinlock();       smp_rmb();
 149  *  spin_unlock(S);     r0 = READ_ONCE(X);              r2 = READ_ONCE(X);
 150  *                      WRITE_ONCE(Y, 1);
 151  *                      spin_unlock(S);
 152  *
 153  *      it is forbidden that CPU0's critical section executes before CPU1's
 154  *      critical section (r0 = 1), CPU2 observes CPU1's store to Y (r1 = 1)
 155  *      and CPU2 does not observe CPU0's store to X (r2 = 0); see the comments
 156  *      preceding the calls to smp_rmb() in try_to_wake_up() for similar
 157  *      snippets but "projected" onto two CPUs.
 158  *
 159  * Property (2) upgrades the lock to an RCsc lock.
 160  *
 161  * Since most load-store architectures implement ACQUIRE with an smp_mb() after
 162  * the LL/SC loop, they need no further barriers. Similarly all our TSO
 163  * architectures imply an smp_mb() for each atomic instruction and equally don't
 164  * need more.
 165  *
 166  * Architectures that can implement ACQUIRE better need to take care.
 167  */
 168 #ifndef smp_mb__after_spinlock
 169 #define smp_mb__after_spinlock()        do { } while (0)
 170 #endif
 171
 172 #ifdef CONFIG_DEBUG_SPINLOCK
 173  extern void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock);
 174 #define do_raw_spin_lock_flags(lock, flags) do_raw_spin_lock(lock)
 175  extern int do_raw_spin_trylock(raw_spinlock_t *lock);
 176  extern void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock);
 177 #else
 178 static inline void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock)
 179 {
 180         __acquire(lock);
 181         arch_spin_lock(&lock->raw_lock);
 182         mmiowb_spin_lock();
 183 }
 184
 185 #ifndef arch_spin_lock_flags
 186 #define arch_spin_lock_flags(lock, flags)       arch_spin_lock(lock)
 187 #endif
 188
 189 static inline void
 190 do_raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long *flags) __acquires(lock)
 191 {
 192         __acquire(lock);
 193         arch_spin_lock_flags(&lock->raw_lock, *flags);
 194         mmiowb_spin_lock();
 195 }
 196
 197 static inline int do_raw_spin_trylock(raw_spinlock_t *lock)
 198 {
 199         int ret = arch_spin_trylock(&(lock)->raw_lock);
 200
 201         if (ret)
 202                 mmiowb_spin_lock();
 203
 204         return ret;
 205 }
 206
 207 static inline void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock)
 208 {
 209         mmiowb_spin_unlock();
 210         arch_spin_unlock(&lock->raw_lock);
 211         __release(lock);
 212 }
 213 #endif
 214
 215 /*
 216  * Define the various spin_lock methods.  Note we define these
 217  * regardless of whether CONFIG_SMP or CONFIG_PREEMPTION are set. The
 218  * various methods are defined as nops in the case they are not
 219  * required.
 220  */
 221 #define raw_spin_trylock(lock)  __cond_lock(lock, _raw_spin_trylock(lock))
 222
 223 #define raw_spin_lock(lock)     _raw_spin_lock(lock)
 224
 225 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 226 # define raw_spin_lock_nested(lock, subclass) \
 227         _raw_spin_lock_nested(lock, subclass)
 228
 229 # define raw_spin_lock_nest_lock(lock, nest_lock)                       \
 230          do {                                                           \
 231                  typecheck(struct lockdep_map *, &(nest_lock)->dep_map);\
 232                  _raw_spin_lock_nest_lock(lock, &(nest_lock)->dep_map); \
 233          } while (0)
 234 #else
 235 /*
 236  * Always evaluate the 'subclass' argument to avoid that the compiler
 237  * warns about set-but-not-used variables when building with
 238  * CONFIG_DEBUG_LOCK_ALLOC=n and with W=1.
 239  */
 240 # define raw_spin_lock_nested(lock, subclass)           \
 241         _raw_spin_lock(((void)(subclass), (lock)))
 242 # define raw_spin_lock_nest_lock(lock, nest_lock)       _raw_spin_lock(lock)
 243 #endif
 244
 245 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
 246
 247 #define raw_spin_lock_irqsave(lock, flags)                      \
 248         do {                                            \
 249                 typecheck(unsigned long, flags);        \
 250                 flags = _raw_spin_lock_irqsave(lock);   \
 251         } while (0)
 252
 253 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 254 #define raw_spin_lock_irqsave_nested(lock, flags, subclass)             \
 255         do {                                                            \
 256                 typecheck(unsigned long, flags);                        \
 257                 flags = _raw_spin_lock_irqsave_nested(lock, subclass);  \
 258         } while (0)
 259 #else
 260 #define raw_spin_lock_irqsave_nested(lock, flags, subclass)             \
 261         do {                                                            \
 262                 typecheck(unsigned long, flags);                        \
 263                 flags = _raw_spin_lock_irqsave(lock);                   \
 264         } while (0)
 265 #endif
 266
 267 #else
 268
 269 #define raw_spin_lock_irqsave(lock, flags)              \
 270         do {                                            \
 271                 typecheck(unsigned long, flags);        \
 272                 _raw_spin_lock_irqsave(lock, flags);    \
 273         } while (0)
 274
 275 #define raw_spin_lock_irqsave_nested(lock, flags, subclass)     \
 276         raw_spin_lock_irqsave(lock, flags)
 277
 278 #endif
 279
 280 #define raw_spin_lock_irq(lock)         _raw_spin_lock_irq(lock)
 281 #define raw_spin_lock_bh(lock)          _raw_spin_lock_bh(lock)
 282 #define raw_spin_unlock(lock)           _raw_spin_unlock(lock)
 283 #define raw_spin_unlock_irq(lock)       _raw_spin_unlock_irq(lock)
 284
 285 #define raw_spin_unlock_irqrestore(lock, flags)         \
 286         do {                                                    \
 287                 typecheck(unsigned long, flags);                \
 288                 _raw_spin_unlock_irqrestore(lock, flags);       \
 289         } while (0)
 290 #define raw_spin_unlock_bh(lock)        _raw_spin_unlock_bh(lock)
 291
 292 #define raw_spin_trylock_bh(lock) \
 293         __cond_lock(lock, _raw_spin_trylock_bh(lock))
 294
 295 #define raw_spin_trylock_irq(lock) \
 296 ({ \
 297         local_irq_disable(); \
 298         raw_spin_trylock(lock) ? \
 299         1 : ({ local_irq_enable(); 0;  }); \
 300 })
 301
 302 #define raw_spin_trylock_irqsave(lock, flags) \
 303 ({ \
 304         local_irq_save(flags); \
 305         raw_spin_trylock(lock) ? \
 306         1 : ({ local_irq_restore(flags); 0; }); \
 307 })
 308
 309 /* Include rwlock functions */
 310 #include <linux/rwlock.h>
 311
 312 /*
 313  * Pull the _spin_*()/_read_*()/_write_*() functions/declarations:
 314  */
 315 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
 316 # include <linux/spinlock_api_smp.h>
 317 #else
 318 # include <linux/spinlock_api_up.h>
 319 #endif
 320
 321 /*
 322  * Map the spin_lock functions to the raw variants for PREEMPT_RT=n
 323  */
 324
 325 static __always_inline raw_spinlock_t *spinlock_check(spinlock_t *lock)
 326 {
 327         return &lock->rlock;
 328 }
 329
 330 #define spin_lock_init(_lock)                           \
 331 do {                                                    \
 332         spinlock_check(_lock);                          \
 333         raw_spin_lock_init(&(_lock)->rlock);            \
 334 } while (0)
 335
 336 static __always_inline void spin_lock(spinlock_t *lock)
 337 {
 338         raw_spin_lock(&lock->rlock);
 339 }
 340
 341 static __always_inline void spin_lock_bh(spinlock_t *lock)
 342 {
 343         raw_spin_lock_bh(&lock->rlock);
 344 }
 345
 346 static __always_inline int spin_trylock(spinlock_t *lock)
 347 {
 348         return raw_spin_trylock(&lock->rlock);
 349 }
 350
 351 #define spin_lock_nested(lock, subclass)                        \
 352 do {                                                            \
 353         raw_spin_lock_nested(spinlock_check(lock), subclass);   \
 354 } while (0)
 355
 356 #define spin_lock_nest_lock(lock, nest_lock)                            \
 357 do {                                                                    \
 358         raw_spin_lock_nest_lock(spinlock_check(lock), nest_lock);       \
 359 } while (0)
 360
 361 static __always_inline void spin_lock_irq(spinlock_t *lock)
 362 {
 363         raw_spin_lock_irq(&lock->rlock);
 364 }
 365
 366 #define spin_lock_irqsave(lock, flags)                          \
 367 do {                                                            \
 368         raw_spin_lock_irqsave(spinlock_check(lock), flags);     \
 369 } while (0)
 370
 371 #define spin_lock_irqsave_nested(lock, flags, subclass)                 \
 372 do {                                                                    \
 373         raw_spin_lock_irqsave_nested(spinlock_check(lock), flags, subclass); \
 374 } while (0)
 375
 376 static __always_inline void spin_unlock(spinlock_t *lock)
 377 {
 378         raw_spin_unlock(&lock->rlock);
 379 }
 380
 381 static __always_inline void spin_unlock_bh(spinlock_t *lock)
 382 {
 383         raw_spin_unlock_bh(&lock->rlock);
 384 }
 385
 386 static __always_inline void spin_unlock_irq(spinlock_t *lock)
 387 {
 388         raw_spin_unlock_irq(&lock->rlock);
 389 }
 390
 391 static __always_inline void spin_unlock_irqrestore(spinlock_t *lock, unsigned long flags)
 392 {
 393         raw_spin_unlock_irqrestore(&lock->rlock, flags);
 394 }
 395
 396 static __always_inline int spin_trylock_bh(spinlock_t *lock)
 397 {
 398         return raw_spin_trylock_bh(&lock->rlock);
 399 }
 400
 401 static __always_inline int spin_trylock_irq(spinlock_t *lock)
 402 {
 403         return raw_spin_trylock_irq(&lock->rlock);
 404 }
 405
 406 #define spin_trylock_irqsave(lock, flags)                       \
 407 ({                                                              \
 408         raw_spin_trylock_irqsave(spinlock_check(lock), flags); \
 409 })
 410
 411 /**
 412  * spin_is_locked() - Check whether a spinlock is locked.
 413  * @lock: Pointer to the spinlock.
 414  *
 415  * This function is NOT required to provide any memory ordering
 416  * guarantees; it could be used for debugging purposes or, when
 417  * additional synchronization is needed, accompanied with other
 418  * constructs (memory barriers) enforcing the synchronization.
 419  *
 420  * Returns: 1 if @lock is locked, 0 otherwise.
 421  *
 422  * Note that the function only tells you that the spinlock is
 423  * seen to be locked, not that it is locked on your CPU.
 424  *
 425  * Further, on CONFIG_SMP=n builds with CONFIG_DEBUG_SPINLOCK=n,
 426  * the return value is always 0 (see include/linux/spinlock_up.h).
 427  * Therefore you should not rely heavily on the return value.
 428  */
 429 static __always_inline int spin_is_locked(spinlock_t *lock)
 430 {
 431         return raw_spin_is_locked(&lock->rlock);
 432 }
 433
 434 static __always_inline int spin_is_contended(spinlock_t *lock)
 435 {
 436         return raw_spin_is_contended(&lock->rlock);
 437 }
 438
 439 #define assert_spin_locked(lock)        assert_raw_spin_locked(&(lock)->rlock)
 440
 441 /*
 442  * Pull the atomic_t declaration:
 443  * (asm-mips/atomic.h needs above definitions)
 444  */
 445 #include <linux/atomic.h>
 446 /**
 447  * atomic_dec_and_lock - lock on reaching reference count zero
 448  * @atomic: the atomic counter
 449  * @lock: the spinlock in question
 450  *
 451  * Decrements @atomic by 1.  If the result is 0, returns true and locks
 452  * @lock.  Returns false for all other cases.
 453  */
 454 extern int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock);
 455 #define atomic_dec_and_lock(atomic, lock) \
 456                 __cond_lock(lock, _atomic_dec_and_lock(atomic, lock))
 457
 458 extern int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock,
 459                                         unsigned long *flags);
 460 #define atomic_dec_and_lock_irqsave(atomic, lock, flags) \
 461                 __cond_lock(lock, _atomic_dec_and_lock_irqsave(atomic, lock, &(flags)))
 462
 463 int __alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *lock_mask,
 464                              size_t max_size, unsigned int cpu_mult,
 465                              gfp_t gfp, const char *name,
 466                              struct lock_class_key *key);
 467
 468 #define alloc_bucket_spinlocks(locks, lock_mask, max_size, cpu_mult, gfp)    \
 469         ({                                                                   \
 470                 static struct lock_class_key key;                            \
 471                 int ret;                                                     \
 472                                                                              \
 473                 ret = __alloc_bucket_spinlocks(locks, lock_mask, max_size,   \
 474                                                cpu_mult, gfp, #locks, &key); \
 475                 ret;                                                         \
 476         })
 477
 478 void free_bucket_spinlocks(spinlock_t *locks);
 479
 480 #endif /* __LINUX_SPINLOCK_H */