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 CONFIG_GENERIC_LOCKBREAK
 111 #define raw_spin_is_contended(lock) ((lock)->break_lock)
 112 #else
 113
 114 #ifdef arch_spin_is_contended
 115 #define raw_spin_is_contended(lock)     arch_spin_is_contended(&(lock)->raw_lock)
 116 #else
 117 #define raw_spin_is_contended(lock)     (((void)(lock), 0))
 118 #endif /*arch_spin_is_contended*/
 119 #endif
 120
 121 /*
 122  * This barrier must provide two things:
 123  *
 124  *   - it must guarantee a STORE before the spin_lock() is ordered against a
 125  *     LOAD after it, see the comments at its two usage sites.
 126  *
 127  *   - it must ensure the critical section is RCsc.
 128  *
 129  * The latter is important for cases where we observe values written by other
 130  * CPUs in spin-loops, without barriers, while being subject to scheduling.
 131  *
 132  * CPU0                 CPU1                    CPU2
 133  *
 134  *                      for (;;) {
 135  *                        if (READ_ONCE(X))
 136  *                          break;
 137  *                      }
 138  * X=1
 139  *                      <sched-out>
 140  *                                              <sched-in>
 141  *                                              r = X;
 142  *
 143  * without transitivity it could be that CPU1 observes X!=0 breaks the loop,
 144  * we get migrated and CPU2 sees X==0.
 145  *
 146  * Since most load-store architectures implement ACQUIRE with an smp_mb() after
 147  * the LL/SC loop, they need no further barriers. Similarly all our TSO
 148  * architectures imply an smp_mb() for each atomic instruction and equally don't
 149  * need more.
 150  *
 151  * Architectures that can implement ACQUIRE better need to take care.
 152  */
 153 #ifndef smp_mb__after_spinlock
 154 #define smp_mb__after_spinlock()        do { } while (0)
 155 #endif
 156
 157 #ifdef CONFIG_DEBUG_SPINLOCK
 158  extern void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock);
 159 #define do_raw_spin_lock_flags(lock, flags) do_raw_spin_lock(lock)
 160  extern int do_raw_spin_trylock(raw_spinlock_t *lock);
 161  extern void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock);
 162 #else
 163 static inline void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock)
 164 {
 165         __acquire(lock);
 166         arch_spin_lock(&lock->raw_lock);
 167 }
 168
 169 #ifndef arch_spin_lock_flags
 170 #define arch_spin_lock_flags(lock, flags)       arch_spin_lock(lock)
 171 #endif
 172
 173 static inline void
 174 do_raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long *flags) __acquires(lock)
 175 {
 176         __acquire(lock);
 177         arch_spin_lock_flags(&lock->raw_lock, *flags);
 178 }
 179
 180 static inline int do_raw_spin_trylock(raw_spinlock_t *lock)
 181 {
 182         return arch_spin_trylock(&(lock)->raw_lock);
 183 }
 184
 185 static inline void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock)
 186 {
 187         arch_spin_unlock(&lock->raw_lock);
 188         __release(lock);
 189 }
 190 #endif
 191
 192 /*
 193  * Define the various spin_lock methods.  Note we define these
 194  * regardless of whether CONFIG_SMP or CONFIG_PREEMPT are set. The
 195  * various methods are defined as nops in the case they are not
 196  * required.
 197  */
 198 #define raw_spin_trylock(lock)  __cond_lock(lock, _raw_spin_trylock(lock))
 199
 200 #define raw_spin_lock(lock)     _raw_spin_lock(lock)
 201
 202 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 203 # define raw_spin_lock_nested(lock, subclass) \
 204         _raw_spin_lock_nested(lock, subclass)
 205
 206 # define raw_spin_lock_nest_lock(lock, nest_lock)                       \
 207          do {                                                           \
 208                  typecheck(struct lockdep_map *, &(nest_lock)->dep_map);\
 209                  _raw_spin_lock_nest_lock(lock, &(nest_lock)->dep_map); \
 210          } while (0)
 211 #else
 212 /*
 213  * Always evaluate the 'subclass' argument to avoid that the compiler
 214  * warns about set-but-not-used variables when building with
 215  * CONFIG_DEBUG_LOCK_ALLOC=n and with W=1.
 216  */
 217 # define raw_spin_lock_nested(lock, subclass)           \
 218         _raw_spin_lock(((void)(subclass), (lock)))
 219 # define raw_spin_lock_nest_lock(lock, nest_lock)       _raw_spin_lock(lock)
 220 #endif
 221
 222 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
 223
 224 #define raw_spin_lock_irqsave(lock, flags)                      \
 225         do {                                            \
 226                 typecheck(unsigned long, flags);        \
 227                 flags = _raw_spin_lock_irqsave(lock);   \
 228         } while (0)
 229
 230 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 231 #define raw_spin_lock_irqsave_nested(lock, flags, subclass)             \
 232         do {                                                            \
 233                 typecheck(unsigned long, flags);                        \
 234                 flags = _raw_spin_lock_irqsave_nested(lock, subclass);  \
 235         } while (0)
 236 #else
 237 #define raw_spin_lock_irqsave_nested(lock, flags, subclass)             \
 238         do {                                                            \
 239                 typecheck(unsigned long, flags);                        \
 240                 flags = _raw_spin_lock_irqsave(lock);                   \
 241         } while (0)
 242 #endif
 243
 244 #else
 245
 246 #define raw_spin_lock_irqsave(lock, flags)              \
 247         do {                                            \
 248                 typecheck(unsigned long, flags);        \
 249                 _raw_spin_lock_irqsave(lock, flags);    \
 250         } while (0)
 251
 252 #define raw_spin_lock_irqsave_nested(lock, flags, subclass)     \
 253         raw_spin_lock_irqsave(lock, flags)
 254
 255 #endif
 256
 257 #define raw_spin_lock_irq(lock)         _raw_spin_lock_irq(lock)
 258 #define raw_spin_lock_bh(lock)          _raw_spin_lock_bh(lock)
 259 #define raw_spin_unlock(lock)           _raw_spin_unlock(lock)
 260 #define raw_spin_unlock_irq(lock)       _raw_spin_unlock_irq(lock)
 261
 262 #define raw_spin_unlock_irqrestore(lock, flags)         \
 263         do {                                                    \
 264                 typecheck(unsigned long, flags);                \
 265                 _raw_spin_unlock_irqrestore(lock, flags);       \
 266         } while (0)
 267 #define raw_spin_unlock_bh(lock)        _raw_spin_unlock_bh(lock)
 268
 269 #define raw_spin_trylock_bh(lock) \
 270         __cond_lock(lock, _raw_spin_trylock_bh(lock))
 271
 272 #define raw_spin_trylock_irq(lock) \
 273 ({ \
 274         local_irq_disable(); \
 275         raw_spin_trylock(lock) ? \
 276         1 : ({ local_irq_enable(); 0;  }); \
 277 })
 278
 279 #define raw_spin_trylock_irqsave(lock, flags) \
 280 ({ \
 281         local_irq_save(flags); \
 282         raw_spin_trylock(lock) ? \
 283         1 : ({ local_irq_restore(flags); 0; }); \
 284 })
 285
 286 /* Include rwlock functions */
 287 #include <linux/rwlock.h>
 288
 289 /*
 290  * Pull the _spin_*()/_read_*()/_write_*() functions/declarations:
 291  */
 292 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
 293 # include <linux/spinlock_api_smp.h>
 294 #else
 295 # include <linux/spinlock_api_up.h>
 296 #endif
 297
 298 /*
 299  * Map the spin_lock functions to the raw variants for PREEMPT_RT=n
 300  */
 301
 302 static __always_inline raw_spinlock_t *spinlock_check(spinlock_t *lock)
 303 {
 304         return &lock->rlock;
 305 }
 306
 307 #define spin_lock_init(_lock)                           \
 308 do {                                                    \
 309         spinlock_check(_lock);                          \
 310         raw_spin_lock_init(&(_lock)->rlock);            \
 311 } while (0)
 312
 313 static __always_inline void spin_lock(spinlock_t *lock)
 314 {
 315         raw_spin_lock(&lock->rlock);
 316 }
 317
 318 static __always_inline void spin_lock_bh(spinlock_t *lock)
 319 {
 320         raw_spin_lock_bh(&lock->rlock);
 321 }
 322
 323 static __always_inline int spin_trylock(spinlock_t *lock)
 324 {
 325         return raw_spin_trylock(&lock->rlock);
 326 }
 327
 328 #define spin_lock_nested(lock, subclass)                        \
 329 do {                                                            \
 330         raw_spin_lock_nested(spinlock_check(lock), subclass);   \
 331 } while (0)
 332
 333 #define spin_lock_nest_lock(lock, nest_lock)                            \
 334 do {                                                                    \
 335         raw_spin_lock_nest_lock(spinlock_check(lock), nest_lock);       \
 336 } while (0)
 337
 338 static __always_inline void spin_lock_irq(spinlock_t *lock)
 339 {
 340         raw_spin_lock_irq(&lock->rlock);
 341 }
 342
 343 #define spin_lock_irqsave(lock, flags)                          \
 344 do {                                                            \
 345         raw_spin_lock_irqsave(spinlock_check(lock), flags);     \
 346 } while (0)
 347
 348 #define spin_lock_irqsave_nested(lock, flags, subclass)                 \
 349 do {                                                                    \
 350         raw_spin_lock_irqsave_nested(spinlock_check(lock), flags, subclass); \
 351 } while (0)
 352
 353 static __always_inline void spin_unlock(spinlock_t *lock)
 354 {
 355         raw_spin_unlock(&lock->rlock);
 356 }
 357
 358 static __always_inline void spin_unlock_bh(spinlock_t *lock)
 359 {
 360         raw_spin_unlock_bh(&lock->rlock);
 361 }
 362
 363 static __always_inline void spin_unlock_irq(spinlock_t *lock)
 364 {
 365         raw_spin_unlock_irq(&lock->rlock);
 366 }
 367
 368 static __always_inline void spin_unlock_irqrestore(spinlock_t *lock, unsigned long flags)
 369 {
 370         raw_spin_unlock_irqrestore(&lock->rlock, flags);
 371 }
 372
 373 static __always_inline int spin_trylock_bh(spinlock_t *lock)
 374 {
 375         return raw_spin_trylock_bh(&lock->rlock);
 376 }
 377
 378 static __always_inline int spin_trylock_irq(spinlock_t *lock)
 379 {
 380         return raw_spin_trylock_irq(&lock->rlock);
 381 }
 382
 383 #define spin_trylock_irqsave(lock, flags)                       \
 384 ({                                                              \
 385         raw_spin_trylock_irqsave(spinlock_check(lock), flags); \
 386 })
 387
 388 static __always_inline int spin_is_locked(spinlock_t *lock)
 389 {
 390         return raw_spin_is_locked(&lock->rlock);
 391 }
 392
 393 static __always_inline int spin_is_contended(spinlock_t *lock)
 394 {
 395         return raw_spin_is_contended(&lock->rlock);
 396 }
 397
 398 #define assert_spin_locked(lock)        assert_raw_spin_locked(&(lock)->rlock)
 399
 400 /*
 401  * Pull the atomic_t declaration:
 402  * (asm-mips/atomic.h needs above definitions)
 403  */
 404 #include <linux/atomic.h>
 405 /**
 406  * atomic_dec_and_lock - lock on reaching reference count zero
 407  * @atomic: the atomic counter
 408  * @lock: the spinlock in question
 409  *
 410  * Decrements @atomic by 1.  If the result is 0, returns true and locks
 411  * @lock.  Returns false for all other cases.
 412  */
 413 extern int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock);
 414 #define atomic_dec_and_lock(atomic, lock) \
 415                 __cond_lock(lock, _atomic_dec_and_lock(atomic, lock))
 416
 417 #endif /* __LINUX_SPINLOCK_H */