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 static inline void
 170 do_raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long *flags) __acquires(lock)
 171 {
 172         __acquire(lock);
 173         arch_spin_lock_flags(&lock->raw_lock, *flags);
 174 }
 175
 176 static inline int do_raw_spin_trylock(raw_spinlock_t *lock)
 177 {
 178         return arch_spin_trylock(&(lock)->raw_lock);
 179 }
 180
 181 static inline void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock)
 182 {
 183         arch_spin_unlock(&lock->raw_lock);
 184         __release(lock);
 185 }
 186 #endif
 187
 188 /*
 189  * Define the various spin_lock methods.  Note we define these
 190  * regardless of whether CONFIG_SMP or CONFIG_PREEMPT are set. The
 191  * various methods are defined as nops in the case they are not
 192  * required.
 193  */
 194 #define raw_spin_trylock(lock)  __cond_lock(lock, _raw_spin_trylock(lock))
 195
 196 #define raw_spin_lock(lock)     _raw_spin_lock(lock)
 197
 198 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 199 # define raw_spin_lock_nested(lock, subclass) \
 200         _raw_spin_lock_nested(lock, subclass)
 201
 202 # define raw_spin_lock_nest_lock(lock, nest_lock)                       \
 203          do {                                                           \
 204                  typecheck(struct lockdep_map *, &(nest_lock)->dep_map);\
 205                  _raw_spin_lock_nest_lock(lock, &(nest_lock)->dep_map); \
 206          } while (0)
 207 #else
 208 /*
 209  * Always evaluate the 'subclass' argument to avoid that the compiler
 210  * warns about set-but-not-used variables when building with
 211  * CONFIG_DEBUG_LOCK_ALLOC=n and with W=1.
 212  */
 213 # define raw_spin_lock_nested(lock, subclass)           \
 214         _raw_spin_lock(((void)(subclass), (lock)))
 215 # define raw_spin_lock_nest_lock(lock, nest_lock)       _raw_spin_lock(lock)
 216 #endif
 217
 218 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
 219
 220 #define raw_spin_lock_irqsave(lock, flags)                      \
 221         do {                                            \
 222                 typecheck(unsigned long, flags);        \
 223                 flags = _raw_spin_lock_irqsave(lock);   \
 224         } while (0)
 225
 226 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 227 #define raw_spin_lock_irqsave_nested(lock, flags, subclass)             \
 228         do {                                                            \
 229                 typecheck(unsigned long, flags);                        \
 230                 flags = _raw_spin_lock_irqsave_nested(lock, subclass);  \
 231         } while (0)
 232 #else
 233 #define raw_spin_lock_irqsave_nested(lock, flags, subclass)             \
 234         do {                                                            \
 235                 typecheck(unsigned long, flags);                        \
 236                 flags = _raw_spin_lock_irqsave(lock);                   \
 237         } while (0)
 238 #endif
 239
 240 #else
 241
 242 #define raw_spin_lock_irqsave(lock, flags)              \
 243         do {                                            \
 244                 typecheck(unsigned long, flags);        \
 245                 _raw_spin_lock_irqsave(lock, flags);    \
 246         } while (0)
 247
 248 #define raw_spin_lock_irqsave_nested(lock, flags, subclass)     \
 249         raw_spin_lock_irqsave(lock, flags)
 250
 251 #endif
 252
 253 #define raw_spin_lock_irq(lock)         _raw_spin_lock_irq(lock)
 254 #define raw_spin_lock_bh(lock)          _raw_spin_lock_bh(lock)
 255 #define raw_spin_unlock(lock)           _raw_spin_unlock(lock)
 256 #define raw_spin_unlock_irq(lock)       _raw_spin_unlock_irq(lock)
 257
 258 #define raw_spin_unlock_irqrestore(lock, flags)         \
 259         do {                                                    \
 260                 typecheck(unsigned long, flags);                \
 261                 _raw_spin_unlock_irqrestore(lock, flags);       \
 262         } while (0)
 263 #define raw_spin_unlock_bh(lock)        _raw_spin_unlock_bh(lock)
 264
 265 #define raw_spin_trylock_bh(lock) \
 266         __cond_lock(lock, _raw_spin_trylock_bh(lock))
 267
 268 #define raw_spin_trylock_irq(lock) \
 269 ({ \
 270         local_irq_disable(); \
 271         raw_spin_trylock(lock) ? \
 272         1 : ({ local_irq_enable(); 0;  }); \
 273 })
 274
 275 #define raw_spin_trylock_irqsave(lock, flags) \
 276 ({ \
 277         local_irq_save(flags); \
 278         raw_spin_trylock(lock) ? \
 279         1 : ({ local_irq_restore(flags); 0; }); \
 280 })
 281
 282 /**
 283  * raw_spin_can_lock - would raw_spin_trylock() succeed?
 284  * @lock: the spinlock in question.
 285  */
 286 #define raw_spin_can_lock(lock) (!raw_spin_is_locked(lock))
 287
 288 /* Include rwlock functions */
 289 #include <linux/rwlock.h>
 290
 291 /*
 292  * Pull the _spin_*()/_read_*()/_write_*() functions/declarations:
 293  */
 294 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
 295 # include <linux/spinlock_api_smp.h>
 296 #else
 297 # include <linux/spinlock_api_up.h>
 298 #endif
 299
 300 /*
 301  * Map the spin_lock functions to the raw variants for PREEMPT_RT=n
 302  */
 303
 304 static __always_inline raw_spinlock_t *spinlock_check(spinlock_t *lock)
 305 {
 306         return &lock->rlock;
 307 }
 308
 309 #define spin_lock_init(_lock)                           \
 310 do {                                                    \
 311         spinlock_check(_lock);                          \
 312         raw_spin_lock_init(&(_lock)->rlock);            \
 313 } while (0)
 314
 315 static __always_inline void spin_lock(spinlock_t *lock)
 316 {
 317         raw_spin_lock(&lock->rlock);
 318 }
 319
 320 static __always_inline void spin_lock_bh(spinlock_t *lock)
 321 {
 322         raw_spin_lock_bh(&lock->rlock);
 323 }
 324
 325 static __always_inline int spin_trylock(spinlock_t *lock)
 326 {
 327         return raw_spin_trylock(&lock->rlock);
 328 }
 329
 330 #define spin_lock_nested(lock, subclass)                        \
 331 do {                                                            \
 332         raw_spin_lock_nested(spinlock_check(lock), subclass);   \
 333 } while (0)
 334
 335 #define spin_lock_nest_lock(lock, nest_lock)                            \
 336 do {                                                                    \
 337         raw_spin_lock_nest_lock(spinlock_check(lock), nest_lock);       \
 338 } while (0)
 339
 340 static __always_inline void spin_lock_irq(spinlock_t *lock)
 341 {
 342         raw_spin_lock_irq(&lock->rlock);
 343 }
 344
 345 #define spin_lock_irqsave(lock, flags)                          \
 346 do {                                                            \
 347         raw_spin_lock_irqsave(spinlock_check(lock), flags);     \
 348 } while (0)
 349
 350 #define spin_lock_irqsave_nested(lock, flags, subclass)                 \
 351 do {                                                                    \
 352         raw_spin_lock_irqsave_nested(spinlock_check(lock), flags, subclass); \
 353 } while (0)
 354
 355 static __always_inline void spin_unlock(spinlock_t *lock)
 356 {
 357         raw_spin_unlock(&lock->rlock);
 358 }
 359
 360 static __always_inline void spin_unlock_bh(spinlock_t *lock)
 361 {
 362         raw_spin_unlock_bh(&lock->rlock);
 363 }
 364
 365 static __always_inline void spin_unlock_irq(spinlock_t *lock)
 366 {
 367         raw_spin_unlock_irq(&lock->rlock);
 368 }
 369
 370 static __always_inline void spin_unlock_irqrestore(spinlock_t *lock, unsigned long flags)
 371 {
 372         raw_spin_unlock_irqrestore(&lock->rlock, flags);
 373 }
 374
 375 static __always_inline int spin_trylock_bh(spinlock_t *lock)
 376 {
 377         return raw_spin_trylock_bh(&lock->rlock);
 378 }
 379
 380 static __always_inline int spin_trylock_irq(spinlock_t *lock)
 381 {
 382         return raw_spin_trylock_irq(&lock->rlock);
 383 }
 384
 385 #define spin_trylock_irqsave(lock, flags)                       \
 386 ({                                                              \
 387         raw_spin_trylock_irqsave(spinlock_check(lock), flags); \
 388 })
 389
 390 static __always_inline int spin_is_locked(spinlock_t *lock)
 391 {
 392         return raw_spin_is_locked(&lock->rlock);
 393 }
 394
 395 static __always_inline int spin_is_contended(spinlock_t *lock)
 396 {
 397         return raw_spin_is_contended(&lock->rlock);
 398 }
 399
 400 static __always_inline int spin_can_lock(spinlock_t *lock)
 401 {
 402         return raw_spin_can_lock(&lock->rlock);
 403 }
 404
 405 #define assert_spin_locked(lock)        assert_raw_spin_locked(&(lock)->rlock)
 406
 407 /*
 408  * Pull the atomic_t declaration:
 409  * (asm-mips/atomic.h needs above definitions)
 410  */
 411 #include <linux/atomic.h>
 412 /**
 413  * atomic_dec_and_lock - lock on reaching reference count zero
 414  * @atomic: the atomic counter
 415  * @lock: the spinlock in question
 416  *
 417  * Decrements @atomic by 1.  If the result is 0, returns true and locks
 418  * @lock.  Returns false for all other cases.
 419  */
 420 extern int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock);
 421 #define atomic_dec_and_lock(atomic, lock) \
 422                 __cond_lock(lock, _atomic_dec_and_lock(atomic, lock))
 423
 424 #endif /* __LINUX_SPINLOCK_H */