1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __LINUX_SPINLOCK_H
3 #define __LINUX_SPINLOCK_H
4 #define __LINUX_INSIDE_SPINLOCK_H
5
6 /*
7 * include/linux/spinlock.h - generic spinlock/rwlock declarations
8 *
9 * here's the role of the various spinlock/rwlock related include files:
10 *
11 * on SMP builds:
12 *
13 * asm/spinlock_types.h: contains the arch_spinlock_t/arch_rwlock_t and the
14 * initializers
15 *
16 * linux/spinlock_types_raw:
17 * The raw types and initializers
18 * linux/spinlock_types.h:
19 * defines the generic type and initializers
20 *
21 * asm/spinlock.h: contains the arch_spin_*()/etc. lowlevel
22 * implementations, mostly inline assembly code
23 *
24 * (also included on UP-debug builds:)
25 *
26 * linux/spinlock_api_smp.h:
27 * contains the prototypes for the _spin_*() APIs.
28 *
29 * linux/spinlock.h: builds the final spin_*() APIs.
30 *
31 * on UP builds:
32 *
33 * linux/spinlock_type_up.h:
34 * contains the generic, simplified UP spinlock type.
35 * (which is an empty structure on non-debug builds)
36 *
37 * linux/spinlock_types_raw:
38 * The raw RT types and initializers
39 * linux/spinlock_types.h:
40 * defines the generic type and initializers
41 *
42 * linux/spinlock_up.h:
43 * contains the arch_spin_*()/etc. version of UP
44 * builds. (which are NOPs on non-debug, non-preempt
45 * builds)
46 *
47 * (included on UP-non-debug builds:)
48 *
49 * linux/spinlock_api_up.h:
50 * builds the _spin_*() APIs.
51 *
52 * linux/spinlock.h: builds the final spin_*() APIs.
53 */
54
55 #include <linux/typecheck.h>
56 #include <linux/preempt.h>
57 #include <linux/linkage.h>
58 #include <linux/compiler.h>
59 #include <linux/irqflags.h>
60 #include <linux/thread_info.h>
61 #include <linux/stringify.h>
62 #include <linux/bottom_half.h>
63 #include <linux/lockdep.h>
64 #include <linux/cleanup.h>
65 #include <asm/barrier.h>
66 #include <asm/mmiowb.h>
67
68
69 /*
70 * Must define these before including other files, inline functions need them
71 */
72 #define LOCK_SECTION_NAME ".text..lock."KBUILD_BASENAME
73
74 #define LOCK_SECTION_START(extra) \
75 ".subsection 1\n\t" \
76 extra \
77 ".ifndef " LOCK_SECTION_NAME "\n\t" \
78 LOCK_SECTION_NAME ":\n\t" \
79 ".endif\n"
80
81 #define LOCK_SECTION_END \
82 ".previous\n\t"
83
84 #define __lockfunc __section(".spinlock.text")
85
86 /*
87 * Pull the arch_spinlock_t and arch_rwlock_t definitions:
88 */
89 #include <linux/spinlock_types.h>
90
91 /*
92 * Pull the arch_spin*() functions/declarations (UP-nondebug doesn't need them):
93 */
94 #ifdef CONFIG_SMP
95 # include <asm/spinlock.h>
96 #else
97 # include <linux/spinlock_up.h>
98 #endif
99
100 #ifdef CONFIG_DEBUG_SPINLOCK
101 extern void __raw_spin_lock_init(raw_spinlock_t *lock, const char *name,
102 struct lock_class_key *key, short inner);
103
104 # define raw_spin_lock_init(lock) \
105 do { \
106 static struct lock_class_key __key; \
107 \
108 __raw_spin_lock_init((lock), #lock, &__key, LD_WAIT_SPIN); \
109 } while (0)
110
111 #else
112 # define raw_spin_lock_init(lock) \
113 do { *(lock) = __RAW_SPIN_LOCK_UNLOCKED(lock); } while (0)
114 #endif
115
116 #define raw_spin_is_locked(lock) arch_spin_is_locked(&(lock)->raw_lock)
117
118 #ifdef arch_spin_is_contended
119 #define raw_spin_is_contended(lock) arch_spin_is_contended(&(lock)->raw_lock)
120 #else
121 #define raw_spin_is_contended(lock) (((void)(lock), 0))
122 #endif /*arch_spin_is_contended*/
123
124 /*
125 * smp_mb__after_spinlock() provides the equivalent of a full memory barrier
126 * between program-order earlier lock acquisitions and program-order later
127 * memory accesses.
128 *
129 * This guarantees that the following two properties hold:
130 *
131 * 1) Given the snippet:
132 *
133 * { X = 0; Y = 0; }
134 *
135 * CPU0 CPU1
136 *
137 * WRITE_ONCE(X, 1); WRITE_ONCE(Y, 1);
138 * spin_lock(S); smp_mb();
139 * smp_mb__after_spinlock(); r1 = READ_ONCE(X);
140 * r0 = READ_ONCE(Y);
141 * spin_unlock(S);
142 *
143 * it is forbidden that CPU0 does not observe CPU1's store to Y (r0 = 0)
144 * and CPU1 does not observe CPU0's store to X (r1 = 0); see the comments
145 * preceding the call to smp_mb__after_spinlock() in __schedule() and in
146 * try_to_wake_up().
147 *
148 * 2) Given the snippet:
149 *
150 * { X = 0; Y = 0; }
151 *
152 * CPU0 CPU1 CPU2
153 *
154 * spin_lock(S); spin_lock(S); r1 = READ_ONCE(Y);
155 * WRITE_ONCE(X, 1); smp_mb__after_spinlock(); smp_rmb();
156 * spin_unlock(S); r0 = READ_ONCE(X); r2 = READ_ONCE(X);
157 * WRITE_ONCE(Y, 1);
158 * spin_unlock(S);
159 *
160 * it is forbidden that CPU0's critical section executes before CPU1's
161 * critical section (r0 = 1), CPU2 observes CPU1's store to Y (r1 = 1)
162 * and CPU2 does not observe CPU0's store to X (r2 = 0); see the comments
163 * preceding the calls to smp_rmb() in try_to_wake_up() for similar
164 * snippets but "projected" onto two CPUs.
165 *
166 * Property (2) upgrades the lock to an RCsc lock.
167 *
168 * Since most load-store architectures implement ACQUIRE with an smp_mb() after
169 * the LL/SC loop, they need no further barriers. Similarly all our TSO
170 * architectures imply an smp_mb() for each atomic instruction and equally don't
171 * need more.
172 *
173 * Architectures that can implement ACQUIRE better need to take care.
174 */
175 #ifndef smp_mb__after_spinlock
176 #define smp_mb__after_spinlock() kcsan_mb()
177 #endif
178
179 #ifdef CONFIG_DEBUG_SPINLOCK
180 extern void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock);
181 extern int do_raw_spin_trylock(raw_spinlock_t *lock);
182 extern void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock);
183 #else
do_raw_spin_lock(raw_spinlock_t * lock)184 static inline void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock)
185 {
186 __acquire(lock);
187 arch_spin_lock(&lock->raw_lock);
188 mmiowb_spin_lock();
189 }
190
do_raw_spin_trylock(raw_spinlock_t * lock)191 static inline int do_raw_spin_trylock(raw_spinlock_t *lock)
192 {
193 int ret = arch_spin_trylock(&(lock)->raw_lock);
194
195 if (ret)
196 mmiowb_spin_lock();
197
198 return ret;
199 }
200
do_raw_spin_unlock(raw_spinlock_t * lock)201 static inline void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock)
202 {
203 mmiowb_spin_unlock();
204 arch_spin_unlock(&lock->raw_lock);
205 __release(lock);
206 }
207 #endif
208
209 /*
210 * Define the various spin_lock methods. Note we define these
211 * regardless of whether CONFIG_SMP or CONFIG_PREEMPTION are set. The
212 * various methods are defined as nops in the case they are not
213 * required.
214 */
215 #define raw_spin_trylock(lock) __cond_lock(lock, _raw_spin_trylock(lock))
216
217 #define raw_spin_lock(lock) _raw_spin_lock(lock)
218
219 #ifdef CONFIG_DEBUG_LOCK_ALLOC
220 # define raw_spin_lock_nested(lock, subclass) \
221 _raw_spin_lock_nested(lock, subclass)
222
223 # define raw_spin_lock_nest_lock(lock, nest_lock) \
224 do { \
225 typecheck(struct lockdep_map *, &(nest_lock)->dep_map);\
226 _raw_spin_lock_nest_lock(lock, &(nest_lock)->dep_map); \
227 } while (0)
228 #else
229 /*
230 * Always evaluate the 'subclass' argument to avoid that the compiler
231 * warns about set-but-not-used variables when building with
232 * CONFIG_DEBUG_LOCK_ALLOC=n and with W=1.
233 */
234 # define raw_spin_lock_nested(lock, subclass) \
235 _raw_spin_lock(((void)(subclass), (lock)))
236 # define raw_spin_lock_nest_lock(lock, nest_lock) _raw_spin_lock(lock)
237 #endif
238
239 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
240
241 #define raw_spin_lock_irqsave(lock, flags) \
242 do { \
243 typecheck(unsigned long, flags); \
244 flags = _raw_spin_lock_irqsave(lock); \
245 } while (0)
246
247 #ifdef CONFIG_DEBUG_LOCK_ALLOC
248 #define raw_spin_lock_irqsave_nested(lock, flags, subclass) \
249 do { \
250 typecheck(unsigned long, flags); \
251 flags = _raw_spin_lock_irqsave_nested(lock, subclass); \
252 } while (0)
253 #else
254 #define raw_spin_lock_irqsave_nested(lock, flags, subclass) \
255 do { \
256 typecheck(unsigned long, flags); \
257 flags = _raw_spin_lock_irqsave(lock); \
258 } while (0)
259 #endif
260
261 #else
262
263 #define raw_spin_lock_irqsave(lock, flags) \
264 do { \
265 typecheck(unsigned long, flags); \
266 _raw_spin_lock_irqsave(lock, flags); \
267 } while (0)
268
269 #define raw_spin_lock_irqsave_nested(lock, flags, subclass) \
270 raw_spin_lock_irqsave(lock, flags)
271
272 #endif
273
274 #define raw_spin_lock_irq(lock) _raw_spin_lock_irq(lock)
275 #define raw_spin_lock_bh(lock) _raw_spin_lock_bh(lock)
276 #define raw_spin_unlock(lock) _raw_spin_unlock(lock)
277 #define raw_spin_unlock_irq(lock) _raw_spin_unlock_irq(lock)
278
279 #define raw_spin_unlock_irqrestore(lock, flags) \
280 do { \
281 typecheck(unsigned long, flags); \
282 _raw_spin_unlock_irqrestore(lock, flags); \
283 } while (0)
284 #define raw_spin_unlock_bh(lock) _raw_spin_unlock_bh(lock)
285
286 #define raw_spin_trylock_bh(lock) \
287 __cond_lock(lock, _raw_spin_trylock_bh(lock))
288
289 #define raw_spin_trylock_irq(lock) \
290 ({ \
291 local_irq_disable(); \
292 raw_spin_trylock(lock) ? \
293 1 : ({ local_irq_enable(); 0; }); \
294 })
295
296 #define raw_spin_trylock_irqsave(lock, flags) \
297 ({ \
298 local_irq_save(flags); \
299 raw_spin_trylock(lock) ? \
300 1 : ({ local_irq_restore(flags); 0; }); \
301 })
302
303 #ifndef CONFIG_PREEMPT_RT
304 /* Include rwlock functions for !RT */
305 #include <linux/rwlock.h>
306 #endif
307
308 /*
309 * Pull the _spin_*()/_read_*()/_write_*() functions/declarations:
310 */
311 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
312 # include <linux/spinlock_api_smp.h>
313 #else
314 # include <linux/spinlock_api_up.h>
315 #endif
316
317 /* Non PREEMPT_RT kernel, map to raw spinlocks: */
318 #ifndef CONFIG_PREEMPT_RT
319
320 /*
321 * Map the spin_lock functions to the raw variants for PREEMPT_RT=n
322 */
323
spinlock_check(spinlock_t * lock)324 static __always_inline raw_spinlock_t *spinlock_check(spinlock_t *lock)
325 {
326 return &lock->rlock;
327 }
328
329 #ifdef CONFIG_DEBUG_SPINLOCK
330
331 # define spin_lock_init(lock) \
332 do { \
333 static struct lock_class_key __key; \
334 \
335 __raw_spin_lock_init(spinlock_check(lock), \
336 #lock, &__key, LD_WAIT_CONFIG); \
337 } while (0)
338
339 #else
340
341 # define spin_lock_init(_lock) \
342 do { \
343 spinlock_check(_lock); \
344 *(_lock) = __SPIN_LOCK_UNLOCKED(_lock); \
345 } while (0)
346
347 #endif
348
spin_lock(spinlock_t * lock)349 static __always_inline void spin_lock(spinlock_t *lock)
350 {
351 raw_spin_lock(&lock->rlock);
352 }
353
spin_lock_bh(spinlock_t * lock)354 static __always_inline void spin_lock_bh(spinlock_t *lock)
355 {
356 raw_spin_lock_bh(&lock->rlock);
357 }
358
spin_trylock(spinlock_t * lock)359 static __always_inline int spin_trylock(spinlock_t *lock)
360 {
361 return raw_spin_trylock(&lock->rlock);
362 }
363
364 #define spin_lock_nested(lock, subclass) \
365 do { \
366 raw_spin_lock_nested(spinlock_check(lock), subclass); \
367 } while (0)
368
369 #define spin_lock_nest_lock(lock, nest_lock) \
370 do { \
371 raw_spin_lock_nest_lock(spinlock_check(lock), nest_lock); \
372 } while (0)
373
spin_lock_irq(spinlock_t * lock)374 static __always_inline void spin_lock_irq(spinlock_t *lock)
375 {
376 raw_spin_lock_irq(&lock->rlock);
377 }
378
379 #define spin_lock_irqsave(lock, flags) \
380 do { \
381 raw_spin_lock_irqsave(spinlock_check(lock), flags); \
382 } while (0)
383
384 #define spin_lock_irqsave_nested(lock, flags, subclass) \
385 do { \
386 raw_spin_lock_irqsave_nested(spinlock_check(lock), flags, subclass); \
387 } while (0)
388
spin_unlock(spinlock_t * lock)389 static __always_inline void spin_unlock(spinlock_t *lock)
390 {
391 raw_spin_unlock(&lock->rlock);
392 }
393
spin_unlock_bh(spinlock_t * lock)394 static __always_inline void spin_unlock_bh(spinlock_t *lock)
395 {
396 raw_spin_unlock_bh(&lock->rlock);
397 }
398
spin_unlock_irq(spinlock_t * lock)399 static __always_inline void spin_unlock_irq(spinlock_t *lock)
400 {
401 raw_spin_unlock_irq(&lock->rlock);
402 }
403
spin_unlock_irqrestore(spinlock_t * lock,unsigned long flags)404 static __always_inline void spin_unlock_irqrestore(spinlock_t *lock, unsigned long flags)
405 {
406 raw_spin_unlock_irqrestore(&lock->rlock, flags);
407 }
408
spin_trylock_bh(spinlock_t * lock)409 static __always_inline int spin_trylock_bh(spinlock_t *lock)
410 {
411 return raw_spin_trylock_bh(&lock->rlock);
412 }
413
spin_trylock_irq(spinlock_t * lock)414 static __always_inline int spin_trylock_irq(spinlock_t *lock)
415 {
416 return raw_spin_trylock_irq(&lock->rlock);
417 }
418
419 #define spin_trylock_irqsave(lock, flags) \
420 ({ \
421 raw_spin_trylock_irqsave(spinlock_check(lock), flags); \
422 })
423
424 /**
425 * spin_is_locked() - Check whether a spinlock is locked.
426 * @lock: Pointer to the spinlock.
427 *
428 * This function is NOT required to provide any memory ordering
429 * guarantees; it could be used for debugging purposes or, when
430 * additional synchronization is needed, accompanied with other
431 * constructs (memory barriers) enforcing the synchronization.
432 *
433 * Returns: 1 if @lock is locked, 0 otherwise.
434 *
435 * Note that the function only tells you that the spinlock is
436 * seen to be locked, not that it is locked on your CPU.
437 *
438 * Further, on CONFIG_SMP=n builds with CONFIG_DEBUG_SPINLOCK=n,
439 * the return value is always 0 (see include/linux/spinlock_up.h).
440 * Therefore you should not rely heavily on the return value.
441 */
spin_is_locked(spinlock_t * lock)442 static __always_inline int spin_is_locked(spinlock_t *lock)
443 {
444 return raw_spin_is_locked(&lock->rlock);
445 }
446
spin_is_contended(spinlock_t * lock)447 static __always_inline int spin_is_contended(spinlock_t *lock)
448 {
449 return raw_spin_is_contended(&lock->rlock);
450 }
451
452 #define assert_spin_locked(lock) assert_raw_spin_locked(&(lock)->rlock)
453
454 #else /* !CONFIG_PREEMPT_RT */
455 # include <linux/spinlock_rt.h>
456 #endif /* CONFIG_PREEMPT_RT */
457
458 /*
459 * Pull the atomic_t declaration:
460 * (asm-mips/atomic.h needs above definitions)
461 */
462 #include <linux/atomic.h>
463 /**
464 * atomic_dec_and_lock - lock on reaching reference count zero
465 * @atomic: the atomic counter
466 * @lock: the spinlock in question
467 *
468 * Decrements @atomic by 1. If the result is 0, returns true and locks
469 * @lock. Returns false for all other cases.
470 */
471 extern int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock);
472 #define atomic_dec_and_lock(atomic, lock) \
473 __cond_lock(lock, _atomic_dec_and_lock(atomic, lock))
474
475 extern int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock,
476 unsigned long *flags);
477 #define atomic_dec_and_lock_irqsave(atomic, lock, flags) \
478 __cond_lock(lock, _atomic_dec_and_lock_irqsave(atomic, lock, &(flags)))
479
480 extern int _atomic_dec_and_raw_lock(atomic_t *atomic, raw_spinlock_t *lock);
481 #define atomic_dec_and_raw_lock(atomic, lock) \
482 __cond_lock(lock, _atomic_dec_and_raw_lock(atomic, lock))
483
484 extern int _atomic_dec_and_raw_lock_irqsave(atomic_t *atomic, raw_spinlock_t *lock,
485 unsigned long *flags);
486 #define atomic_dec_and_raw_lock_irqsave(atomic, lock, flags) \
487 __cond_lock(lock, _atomic_dec_and_raw_lock_irqsave(atomic, lock, &(flags)))
488
489 int __alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *lock_mask,
490 size_t max_size, unsigned int cpu_mult,
491 gfp_t gfp, const char *name,
492 struct lock_class_key *key);
493
494 #define alloc_bucket_spinlocks(locks, lock_mask, max_size, cpu_mult, gfp) \
495 ({ \
496 static struct lock_class_key key; \
497 int ret; \
498 \
499 ret = __alloc_bucket_spinlocks(locks, lock_mask, max_size, \
500 cpu_mult, gfp, #locks, &key); \
501 ret; \
502 })
503
504 void free_bucket_spinlocks(spinlock_t *locks);
505
506 DEFINE_LOCK_GUARD_1(raw_spinlock, raw_spinlock_t,
507 raw_spin_lock(_T->lock),
508 raw_spin_unlock(_T->lock))
509
510 DEFINE_LOCK_GUARD_1(raw_spinlock_nested, raw_spinlock_t,
511 raw_spin_lock_nested(_T->lock, SINGLE_DEPTH_NESTING),
512 raw_spin_unlock(_T->lock))
513
514 DEFINE_LOCK_GUARD_1(raw_spinlock_irq, raw_spinlock_t,
515 raw_spin_lock_irq(_T->lock),
516 raw_spin_unlock_irq(_T->lock))
517
518 DEFINE_LOCK_GUARD_1(raw_spinlock_irqsave, raw_spinlock_t,
519 raw_spin_lock_irqsave(_T->lock, _T->flags),
520 raw_spin_unlock_irqrestore(_T->lock, _T->flags),
521 unsigned long flags)
522
523 DEFINE_LOCK_GUARD_1(spinlock, spinlock_t,
524 spin_lock(_T->lock),
525 spin_unlock(_T->lock))
526
527 DEFINE_LOCK_GUARD_1(spinlock_irq, spinlock_t,
528 spin_lock_irq(_T->lock),
529 spin_unlock_irq(_T->lock))
530
531 DEFINE_LOCK_GUARD_1(spinlock_irqsave, spinlock_t,
532 spin_lock_irqsave(_T->lock, _T->flags),
533 spin_unlock_irqrestore(_T->lock, _T->flags),
534 unsigned long flags)
535
536 #undef __LINUX_INSIDE_SPINLOCK_H
537 #endif /* __LINUX_SPINLOCK_H */
538