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  * Despite its name it doesn't necessarily has to be a full barrier.
 122  * It should only guarantee that a STORE before the critical section
 123  * can not be reordered with LOADs and STOREs inside this section.
 124  * spin_lock() is the one-way barrier, this LOAD can not escape out
 125  * of the region. So the default implementation simply ensures that
 126  * a STORE can not move into the critical section, smp_wmb() should
 127  * serialize it with another STORE done by spin_lock().
 128  */
 129 #ifndef smp_mb__before_spinlock
 130 #define smp_mb__before_spinlock()       smp_wmb()
 131 #endif
 132
 133 /**
 134  * raw_spin_unlock_wait - wait until the spinlock gets unlocked
 135  * @lock: the spinlock in question.
 136  */
 137 #define raw_spin_unlock_wait(lock)      arch_spin_unlock_wait(&(lock)->raw_lock)
 138
 139 #ifdef CONFIG_DEBUG_SPINLOCK
 140  extern void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock);
 141 #define do_raw_spin_lock_flags(lock, flags) do_raw_spin_lock(lock)
 142  extern int do_raw_spin_trylock(raw_spinlock_t *lock);
 143  extern void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock);
 144 #else
 145 static inline void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock)
 146 {
 147         __acquire(lock);
 148         arch_spin_lock(&lock->raw_lock);
 149 }
 150
 151 static inline void
 152 do_raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long *flags) __acquires(lock)
 153 {
 154         __acquire(lock);
 155         arch_spin_lock_flags(&lock->raw_lock, *flags);
 156 }
 157
 158 static inline int do_raw_spin_trylock(raw_spinlock_t *lock)
 159 {
 160         return arch_spin_trylock(&(lock)->raw_lock);
 161 }
 162
 163 static inline void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock)
 164 {
 165         arch_spin_unlock(&lock->raw_lock);
 166         __release(lock);
 167 }
 168 #endif
 169
 170 /*
 171  * Define the various spin_lock methods.  Note we define these
 172  * regardless of whether CONFIG_SMP or CONFIG_PREEMPT are set. The
 173  * various methods are defined as nops in the case they are not
 174  * required.
 175  */
 176 #define raw_spin_trylock(lock)  __cond_lock(lock, _raw_spin_trylock(lock))
 177
 178 #define raw_spin_lock(lock)     _raw_spin_lock(lock)
 179
 180 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 181 # define raw_spin_lock_nested(lock, subclass) \
 182         _raw_spin_lock_nested(lock, subclass)
 183
 184 # define raw_spin_lock_nest_lock(lock, nest_lock)                       \
 185          do {                                                           \
 186                  typecheck(struct lockdep_map *, &(nest_lock)->dep_map);\
 187                  _raw_spin_lock_nest_lock(lock, &(nest_lock)->dep_map); \
 188          } while (0)
 189 #else
 190 /*
 191  * Always evaluate the 'subclass' argument to avoid that the compiler
 192  * warns about set-but-not-used variables when building with
 193  * CONFIG_DEBUG_LOCK_ALLOC=n and with W=1.
 194  */
 195 # define raw_spin_lock_nested(lock, subclass)           \
 196         _raw_spin_lock(((void)(subclass), (lock)))
 197 # define raw_spin_lock_nest_lock(lock, nest_lock)       _raw_spin_lock(lock)
 198 #endif
 199
 200 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
 201
 202 #define raw_spin_lock_irqsave(lock, flags)                      \
 203         do {                                            \
 204                 typecheck(unsigned long, flags);        \
 205                 flags = _raw_spin_lock_irqsave(lock);   \
 206         } while (0)
 207
 208 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 209 #define raw_spin_lock_irqsave_nested(lock, flags, subclass)             \
 210         do {                                                            \
 211                 typecheck(unsigned long, flags);                        \
 212                 flags = _raw_spin_lock_irqsave_nested(lock, subclass);  \
 213         } while (0)
 214 #else
 215 #define raw_spin_lock_irqsave_nested(lock, flags, subclass)             \
 216         do {                                                            \
 217                 typecheck(unsigned long, flags);                        \
 218                 flags = _raw_spin_lock_irqsave(lock);                   \
 219         } while (0)
 220 #endif
 221
 222 #else
 223
 224 #define raw_spin_lock_irqsave(lock, flags)              \
 225         do {                                            \
 226                 typecheck(unsigned long, flags);        \
 227                 _raw_spin_lock_irqsave(lock, flags);    \
 228         } while (0)
 229
 230 #define raw_spin_lock_irqsave_nested(lock, flags, subclass)     \
 231         raw_spin_lock_irqsave(lock, flags)
 232
 233 #endif
 234
 235 #define raw_spin_lock_irq(lock)         _raw_spin_lock_irq(lock)
 236 #define raw_spin_lock_bh(lock)          _raw_spin_lock_bh(lock)
 237 #define raw_spin_unlock(lock)           _raw_spin_unlock(lock)
 238 #define raw_spin_unlock_irq(lock)       _raw_spin_unlock_irq(lock)
 239
 240 #define raw_spin_unlock_irqrestore(lock, flags)         \
 241         do {                                                    \
 242                 typecheck(unsigned long, flags);                \
 243                 _raw_spin_unlock_irqrestore(lock, flags);       \
 244         } while (0)
 245 #define raw_spin_unlock_bh(lock)        _raw_spin_unlock_bh(lock)
 246
 247 #define raw_spin_trylock_bh(lock) \
 248         __cond_lock(lock, _raw_spin_trylock_bh(lock))
 249
 250 #define raw_spin_trylock_irq(lock) \
 251 ({ \
 252         local_irq_disable(); \
 253         raw_spin_trylock(lock) ? \
 254         1 : ({ local_irq_enable(); 0;  }); \
 255 })
 256
 257 #define raw_spin_trylock_irqsave(lock, flags) \
 258 ({ \
 259         local_irq_save(flags); \
 260         raw_spin_trylock(lock) ? \
 261         1 : ({ local_irq_restore(flags); 0; }); \
 262 })
 263
 264 /**
 265  * raw_spin_can_lock - would raw_spin_trylock() succeed?
 266  * @lock: the spinlock in question.
 267  */
 268 #define raw_spin_can_lock(lock) (!raw_spin_is_locked(lock))
 269
 270 /* Include rwlock functions */
 271 #include <linux/rwlock.h>
 272
 273 /*
 274  * Pull the _spin_*()/_read_*()/_write_*() functions/declarations:
 275  */
 276 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
 277 # include <linux/spinlock_api_smp.h>
 278 #else
 279 # include <linux/spinlock_api_up.h>
 280 #endif
 281
 282 /*
 283  * Map the spin_lock functions to the raw variants for PREEMPT_RT=n
 284  */
 285
 286 static __always_inline raw_spinlock_t *spinlock_check(spinlock_t *lock)
 287 {
 288         return &lock->rlock;
 289 }
 290
 291 #define spin_lock_init(_lock)                           \
 292 do {                                                    \
 293         spinlock_check(_lock);                          \
 294         raw_spin_lock_init(&(_lock)->rlock);            \
 295 } while (0)
 296
 297 static __always_inline void spin_lock(spinlock_t *lock)
 298 {
 299         raw_spin_lock(&lock->rlock);
 300 }
 301
 302 static __always_inline void spin_lock_bh(spinlock_t *lock)
 303 {
 304         raw_spin_lock_bh(&lock->rlock);
 305 }
 306
 307 static __always_inline int spin_trylock(spinlock_t *lock)
 308 {
 309         return raw_spin_trylock(&lock->rlock);
 310 }
 311
 312 #define spin_lock_nested(lock, subclass)                        \
 313 do {                                                            \
 314         raw_spin_lock_nested(spinlock_check(lock), subclass);   \
 315 } while (0)
 316
 317 #define spin_lock_nest_lock(lock, nest_lock)                            \
 318 do {                                                                    \
 319         raw_spin_lock_nest_lock(spinlock_check(lock), nest_lock);       \
 320 } while (0)
 321
 322 static __always_inline void spin_lock_irq(spinlock_t *lock)
 323 {
 324         raw_spin_lock_irq(&lock->rlock);
 325 }
 326
 327 #define spin_lock_irqsave(lock, flags)                          \
 328 do {                                                            \
 329         raw_spin_lock_irqsave(spinlock_check(lock), flags);     \
 330 } while (0)
 331
 332 #define spin_lock_irqsave_nested(lock, flags, subclass)                 \
 333 do {                                                                    \
 334         raw_spin_lock_irqsave_nested(spinlock_check(lock), flags, subclass); \
 335 } while (0)
 336
 337 static __always_inline void spin_unlock(spinlock_t *lock)
 338 {
 339         raw_spin_unlock(&lock->rlock);
 340 }
 341
 342 static __always_inline void spin_unlock_bh(spinlock_t *lock)
 343 {
 344         raw_spin_unlock_bh(&lock->rlock);
 345 }
 346
 347 static __always_inline void spin_unlock_irq(spinlock_t *lock)
 348 {
 349         raw_spin_unlock_irq(&lock->rlock);
 350 }
 351
 352 static __always_inline void spin_unlock_irqrestore(spinlock_t *lock, unsigned long flags)
 353 {
 354         raw_spin_unlock_irqrestore(&lock->rlock, flags);
 355 }
 356
 357 static __always_inline int spin_trylock_bh(spinlock_t *lock)
 358 {
 359         return raw_spin_trylock_bh(&lock->rlock);
 360 }
 361
 362 static __always_inline int spin_trylock_irq(spinlock_t *lock)
 363 {
 364         return raw_spin_trylock_irq(&lock->rlock);
 365 }
 366
 367 #define spin_trylock_irqsave(lock, flags)                       \
 368 ({                                                              \
 369         raw_spin_trylock_irqsave(spinlock_check(lock), flags); \
 370 })
 371
 372 /**
 373  * spin_unlock_wait - Interpose between successive critical sections
 374  * @lock: the spinlock whose critical sections are to be interposed.
 375  *
 376  * Semantically this is equivalent to a spin_lock() immediately
 377  * followed by a spin_unlock().  However, most architectures have
 378  * more efficient implementations in which the spin_unlock_wait()
 379  * cannot block concurrent lock acquisition, and in some cases
 380  * where spin_unlock_wait() does not write to the lock variable.
 381  * Nevertheless, spin_unlock_wait() can have high overhead, so if
 382  * you feel the need to use it, please check to see if there is
 383  * a better way to get your job done.
 384  *
 385  * The ordering guarantees provided by spin_unlock_wait() are:
 386  *
 387  * 1.  All accesses preceding the spin_unlock_wait() happen before
 388  *     any accesses in later critical sections for this same lock.
 389  * 2.  All accesses following the spin_unlock_wait() happen after
 390  *     any accesses in earlier critical sections for this same lock.
 391  */
 392 static __always_inline void spin_unlock_wait(spinlock_t *lock)
 393 {
 394         raw_spin_unlock_wait(&lock->rlock);
 395 }
 396
 397 static __always_inline int spin_is_locked(spinlock_t *lock)
 398 {
 399         return raw_spin_is_locked(&lock->rlock);
 400 }
 401
 402 static __always_inline int spin_is_contended(spinlock_t *lock)
 403 {
 404         return raw_spin_is_contended(&lock->rlock);
 405 }
 406
 407 static __always_inline int spin_can_lock(spinlock_t *lock)
 408 {
 409         return raw_spin_can_lock(&lock->rlock);
 410 }
 411
 412 #define assert_spin_locked(lock)        assert_raw_spin_locked(&(lock)->rlock)
 413
 414 /*
 415  * Pull the atomic_t declaration:
 416  * (asm-mips/atomic.h needs above definitions)
 417  */
 418 #include <linux/atomic.h>
 419 /**
 420  * atomic_dec_and_lock - lock on reaching reference count zero
 421  * @atomic: the atomic counter
 422  * @lock: the spinlock in question
 423  *
 424  * Decrements @atomic by 1.  If the result is 0, returns true and locks
 425  * @lock.  Returns false for all other cases.
 426  */
 427 extern int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock);
 428 #define atomic_dec_and_lock(atomic, lock) \
 429                 __cond_lock(lock, _atomic_dec_and_lock(atomic, lock))
 430
 431 #endif /* __LINUX_SPINLOCK_H */