include/linux/spinlock.h

   1 #ifndef __LINUX_SPINLOCK_H
   2 #define __LINUX_SPINLOCK_H
   3
   4 /*
   5  * include/linux/spinlock.h - generic spinlock/rwlock declarations
   6  *
   7  * here's the role of the various spinlock/rwlock related include files:
   8  *
   9  * on SMP builds:
  10  *
  11  *  asm/spinlock_types.h: contains the arch_spinlock_t/arch_rwlock_t and the
  12  *                        initializers
  13  *
  14  *  linux/spinlock_types.h:
  15  *                        defines the generic type and initializers
  16  *
  17  *  asm/spinlock.h:       contains the arch_spin_*()/etc. lowlevel
  18  *                        implementations, mostly inline assembly code
  19  *
  20  *   (also included on UP-debug builds:)
  21  *
  22  *  linux/spinlock_api_smp.h:
  23  *                        contains the prototypes for the _spin_*() APIs.
  24  *
  25  *  linux/spinlock.h:     builds the final spin_*() APIs.
  26  *
  27  * on UP builds:
  28  *
  29  *  linux/spinlock_type_up.h:
  30  *                        contains the generic, simplified UP spinlock type.
  31  *                        (which is an empty structure on non-debug builds)
  32  *
  33  *  linux/spinlock_types.h:
  34  *                        defines the generic type and initializers
  35  *
  36  *  linux/spinlock_up.h:
  37  *                        contains the arch_spin_*()/etc. version of UP
  38  *                        builds. (which are NOPs on non-debug, non-preempt
  39  *                        builds)
  40  *
  41  *   (included on UP-non-debug builds:)
  42  *
  43  *  linux/spinlock_api_up.h:
  44  *                        builds the _spin_*() APIs.
  45  *
  46  *  linux/spinlock.h:     builds the final spin_*() APIs.
  47  */
  48
  49 #include <linux/typecheck.h>
  50 #include <linux/preempt.h>
  51 #include <linux/linkage.h>
  52 #include <linux/compiler.h>
  53 #include <linux/irqflags.h>
  54 #include <linux/thread_info.h>
  55 #include <linux/kernel.h>
  56 #include <linux/stringify.h>
  57 #include <linux/bottom_half.h>
  58 #include <asm/barrier.h>
  59
  60
  61 /*
  62  * Must define these before including other files, inline functions need them
  63  */
  64 #define LOCK_SECTION_NAME ".text..lock."KBUILD_BASENAME
  65
  66 #define LOCK_SECTION_START(extra)               \
  67         ".subsection 1\n\t"                     \
  68         extra                                   \
  69         ".ifndef " LOCK_SECTION_NAME "\n\t"     \
  70         LOCK_SECTION_NAME ":\n\t"               \
  71         ".endif\n"
  72
  73 #define LOCK_SECTION_END                        \
  74         ".previous\n\t"
  75
  76 #define __lockfunc __attribute__((section(".spinlock.text")))
  77
  78 /*
  79  * Pull the arch_spinlock_t and arch_rwlock_t definitions:
  80  */
  81 #include <linux/spinlock_types.h>
  82
  83 /*
  84  * Pull the arch_spin*() functions/declarations (UP-nondebug doesn't need them):
  85  */
  86 #ifdef CONFIG_SMP
  87 # include <asm/spinlock.h>
  88 #else
  89 # include <linux/spinlock_up.h>
  90 #endif
  91
  92 #ifdef CONFIG_DEBUG_SPINLOCK
  93   extern void __raw_spin_lock_init(raw_spinlock_t *lock, const char *name,
  94                                    struct lock_class_key *key);
  95 # define raw_spin_lock_init(lock)                               \
  96 do {                                                            \
  97         static struct lock_class_key __key;                     \
  98                                                                 \
  99         __raw_spin_lock_init((lock), #lock, &__key);            \
 100 } while (0)
 101
 102 #else
 103 # define raw_spin_lock_init(lock)                               \
 104         do { *(lock) = __RAW_SPIN_LOCK_UNLOCKED(lock); } while (0)
 105 #endif
 106
 107 #define raw_spin_is_locked(lock)        arch_spin_is_locked(&(lock)->raw_lock)
 108
 109 #ifdef CONFIG_GENERIC_LOCKBREAK
 110 #define raw_spin_is_contended(lock) ((lock)->break_lock)
 111 #else
 112
 113 #ifdef arch_spin_is_contended
 114 #define raw_spin_is_contended(lock)     arch_spin_is_contended(&(lock)->raw_lock)
 115 #else
 116 #define raw_spin_is_contended(lock)     (((void)(lock), 0))
 117 #endif /*arch_spin_is_contended*/
 118 #endif
 119
 120 /*
 121  * This barrier must provide two things:
 122  *
 123  *   - it must guarantee a STORE before the spin_lock() is ordered against a
 124  *     LOAD after it, see the comments at its two usage sites.
 125  *
 126  *   - it must ensure the critical section is RCsc.
 127  *
 128  * The latter is important for cases where we observe values written by other
 129  * CPUs in spin-loops, without barriers, while being subject to scheduling.
 130  *
 131  * CPU0                 CPU1                    CPU2
 132  *
 133  *                      for (;;) {
 134  *                        if (READ_ONCE(X))
 135  *                          break;
 136  *                      }
 137  * X=1
 138  *                      <sched-out>
 139  *                                              <sched-in>
 140  *                                              r = X;
 141  *
 142  * without transitivity it could be that CPU1 observes X!=0 breaks the loop,
 143  * we get migrated and CPU2 sees X==0.
 144  *
 145  * Since most load-store architectures implement ACQUIRE with an smp_mb() after
 146  * the LL/SC loop, they need no further barriers. Similarly all our TSO
 147  * architectures imply an smp_mb() for each atomic instruction and equally don't
 148  * need more.
 149  *
 150  * Architectures that can implement ACQUIRE better need to take care.
 151  */
 152 #ifndef smp_mb__after_spinlock
 153 #define smp_mb__after_spinlock()        do { } while (0)
 154 #endif
 155
 156 #ifdef CONFIG_DEBUG_SPINLOCK
 157  extern void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock);
 158 #define do_raw_spin_lock_flags(lock, flags) do_raw_spin_lock(lock)
 159  extern int do_raw_spin_trylock(raw_spinlock_t *lock);
 160  extern void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock);
 161 #else
 162 static inline void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock)
 163 {
 164         __acquire(lock);
 165         arch_spin_lock(&lock->raw_lock);
 166 }
 167
 168 static inline void
 169 do_raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long *flags) __acquires(lock)
 170 {
 171         __acquire(lock);
 172         arch_spin_lock_flags(&lock->raw_lock, *flags);
 173 }
 174
 175 static inline int do_raw_spin_trylock(raw_spinlock_t *lock)
 176 {
 177         return arch_spin_trylock(&(lock)->raw_lock);
 178 }
 179
 180 static inline void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock)
 181 {
 182         arch_spin_unlock(&lock->raw_lock);
 183         __release(lock);
 184 }
 185 #endif
 186
 187 /*
 188  * Define the various spin_lock methods.  Note we define these
 189  * regardless of whether CONFIG_SMP or CONFIG_PREEMPT are set. The
 190  * various methods are defined as nops in the case they are not
 191  * required.
 192  */
 193 #define raw_spin_trylock(lock)  __cond_lock(lock, _raw_spin_trylock(lock))
 194
 195 #define raw_spin_lock(lock)     _raw_spin_lock(lock)
 196
 197 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 198 # define raw_spin_lock_nested(lock, subclass) \
 199         _raw_spin_lock_nested(lock, subclass)
 200
 201 # define raw_spin_lock_nest_lock(lock, nest_lock)                       \
 202          do {                                                           \
 203                  typecheck(struct lockdep_map *, &(nest_lock)->dep_map);\
 204                  _raw_spin_lock_nest_lock(lock, &(nest_lock)->dep_map); \
 205          } while (0)
 206 #else
 207 /*
 208  * Always evaluate the 'subclass' argument to avoid that the compiler
 209  * warns about set-but-not-used variables when building with
 210  * CONFIG_DEBUG_LOCK_ALLOC=n and with W=1.
 211  */
 212 # define raw_spin_lock_nested(lock, subclass)           \
 213         _raw_spin_lock(((void)(subclass), (lock)))
 214 # define raw_spin_lock_nest_lock(lock, nest_lock)       _raw_spin_lock(lock)
 215 #endif
 216
 217 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
 218
 219 #define raw_spin_lock_irqsave(lock, flags)                      \
 220         do {                                            \
 221                 typecheck(unsigned long, flags);        \
 222                 flags = _raw_spin_lock_irqsave(lock);   \
 223         } while (0)
 224
 225 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 226 #define raw_spin_lock_irqsave_nested(lock, flags, subclass)             \
 227         do {                                                            \
 228                 typecheck(unsigned long, flags);                        \
 229                 flags = _raw_spin_lock_irqsave_nested(lock, subclass);  \
 230         } while (0)
 231 #else
 232 #define raw_spin_lock_irqsave_nested(lock, flags, subclass)             \
 233         do {                                                            \
 234                 typecheck(unsigned long, flags);                        \
 235                 flags = _raw_spin_lock_irqsave(lock);                   \
 236         } while (0)
 237 #endif
 238
 239 #else
 240
 241 #define raw_spin_lock_irqsave(lock, flags)              \
 242         do {                                            \
 243                 typecheck(unsigned long, flags);        \
 244                 _raw_spin_lock_irqsave(lock, flags);    \
 245         } while (0)
 246
 247 #define raw_spin_lock_irqsave_nested(lock, flags, subclass)     \
 248         raw_spin_lock_irqsave(lock, flags)
 249
 250 #endif
 251
 252 #define raw_spin_lock_irq(lock)         _raw_spin_lock_irq(lock)
 253 #define raw_spin_lock_bh(lock)          _raw_spin_lock_bh(lock)
 254 #define raw_spin_unlock(lock)           _raw_spin_unlock(lock)
 255 #define raw_spin_unlock_irq(lock)       _raw_spin_unlock_irq(lock)
 256
 257 #define raw_spin_unlock_irqrestore(lock, flags)         \
 258         do {                                                    \
 259                 typecheck(unsigned long, flags);                \
 260                 _raw_spin_unlock_irqrestore(lock, flags);       \
 261         } while (0)
 262 #define raw_spin_unlock_bh(lock)        _raw_spin_unlock_bh(lock)
 263
 264 #define raw_spin_trylock_bh(lock) \
 265         __cond_lock(lock, _raw_spin_trylock_bh(lock))
 266
 267 #define raw_spin_trylock_irq(lock) \
 268 ({ \
 269         local_irq_disable(); \
 270         raw_spin_trylock(lock) ? \
 271         1 : ({ local_irq_enable(); 0;  }); \
 272 })
 273
 274 #define raw_spin_trylock_irqsave(lock, flags) \
 275 ({ \
 276         local_irq_save(flags); \
 277         raw_spin_trylock(lock) ? \
 278         1 : ({ local_irq_restore(flags); 0; }); \
 279 })
 280
 281 /**
 282  * raw_spin_can_lock - would raw_spin_trylock() succeed?
 283  * @lock: the spinlock in question.
 284  */
 285 #define raw_spin_can_lock(lock) (!raw_spin_is_locked(lock))
 286
 287 /* Include rwlock functions */
 288 #include <linux/rwlock.h>
 289
 290 /*
 291  * Pull the _spin_*()/_read_*()/_write_*() functions/declarations:
 292  */
 293 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
 294 # include <linux/spinlock_api_smp.h>
 295 #else
 296 # include <linux/spinlock_api_up.h>
 297 #endif
 298
 299 /*
 300  * Map the spin_lock functions to the raw variants for PREEMPT_RT=n
 301  */
 302
 303 static __always_inline raw_spinlock_t *spinlock_check(spinlock_t *lock)
 304 {
 305         return &lock->rlock;
 306 }
 307
 308 #define spin_lock_init(_lock)                           \
 309 do {                                                    \
 310         spinlock_check(_lock);                          \
 311         raw_spin_lock_init(&(_lock)->rlock);            \
 312 } while (0)
 313
 314 static __always_inline void spin_lock(spinlock_t *lock)
 315 {
 316         raw_spin_lock(&lock->rlock);
 317 }
 318
 319 static __always_inline void spin_lock_bh(spinlock_t *lock)
 320 {
 321         raw_spin_lock_bh(&lock->rlock);
 322 }
 323
 324 static __always_inline int spin_trylock(spinlock_t *lock)
 325 {
 326         return raw_spin_trylock(&lock->rlock);
 327 }
 328
 329 #define spin_lock_nested(lock, subclass)                        \
 330 do {                                                            \
 331         raw_spin_lock_nested(spinlock_check(lock), subclass);   \
 332 } while (0)
 333
 334 #define spin_lock_nest_lock(lock, nest_lock)                            \
 335 do {                                                                    \
 336         raw_spin_lock_nest_lock(spinlock_check(lock), nest_lock);       \
 337 } while (0)
 338
 339 static __always_inline void spin_lock_irq(spinlock_t *lock)
 340 {
 341         raw_spin_lock_irq(&lock->rlock);
 342 }
 343
 344 #define spin_lock_irqsave(lock, flags)                          \
 345 do {                                                            \
 346         raw_spin_lock_irqsave(spinlock_check(lock), flags);     \
 347 } while (0)
 348
 349 #define spin_lock_irqsave_nested(lock, flags, subclass)                 \
 350 do {                                                                    \
 351         raw_spin_lock_irqsave_nested(spinlock_check(lock), flags, subclass); \
 352 } while (0)
 353
 354 static __always_inline void spin_unlock(spinlock_t *lock)
 355 {
 356         raw_spin_unlock(&lock->rlock);
 357 }
 358
 359 static __always_inline void spin_unlock_bh(spinlock_t *lock)
 360 {
 361         raw_spin_unlock_bh(&lock->rlock);
 362 }
 363
 364 static __always_inline void spin_unlock_irq(spinlock_t *lock)
 365 {
 366         raw_spin_unlock_irq(&lock->rlock);
 367 }
 368
 369 static __always_inline void spin_unlock_irqrestore(spinlock_t *lock, unsigned long flags)
 370 {
 371         raw_spin_unlock_irqrestore(&lock->rlock, flags);
 372 }
 373
 374 static __always_inline int spin_trylock_bh(spinlock_t *lock)
 375 {
 376         return raw_spin_trylock_bh(&lock->rlock);
 377 }
 378
 379 static __always_inline int spin_trylock_irq(spinlock_t *lock)
 380 {
 381         return raw_spin_trylock_irq(&lock->rlock);
 382 }
 383
 384 #define spin_trylock_irqsave(lock, flags)                       \
 385 ({                                                              \
 386         raw_spin_trylock_irqsave(spinlock_check(lock), flags); \
 387 })
 388
 389 static __always_inline int spin_is_locked(spinlock_t *lock)
 390 {
 391         return raw_spin_is_locked(&lock->rlock);
 392 }
 393
 394 static __always_inline int spin_is_contended(spinlock_t *lock)
 395 {
 396         return raw_spin_is_contended(&lock->rlock);
 397 }
 398
 399 static __always_inline int spin_can_lock(spinlock_t *lock)
 400 {
 401         return raw_spin_can_lock(&lock->rlock);
 402 }
 403
 404 #define assert_spin_locked(lock)        assert_raw_spin_locked(&(lock)->rlock)
 405
 406 /*
 407  * Pull the atomic_t declaration:
 408  * (asm-mips/atomic.h needs above definitions)
 409  */
 410 #include <linux/atomic.h>
 411 /**
 412  * atomic_dec_and_lock - lock on reaching reference count zero
 413  * @atomic: the atomic counter
 414  * @lock: the spinlock in question
 415  *
 416  * Decrements @atomic by 1.  If the result is 0, returns true and locks
 417  * @lock.  Returns false for all other cases.
 418  */
 419 extern int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock);
 420 #define atomic_dec_and_lock(atomic, lock) \
 421                 __cond_lock(lock, _atomic_dec_and_lock(atomic, lock))
 422
 423 #endif /* __LINUX_SPINLOCK_H */