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 arch_spin_is_contended
111 #define raw_spin_is_contended(lock) arch_spin_is_contended(&(lock)->raw_lock)
112 #else
113 #define raw_spin_is_contended(lock) (((void)(lock), 0))
114 #endif /*arch_spin_is_contended*/
115
116 /*
117 * smp_mb__after_spinlock() provides the equivalent of a full memory barrier
118 * between program-order earlier lock acquisitions and program-order later
119 * memory accesses.
120 *
121 * This guarantees that the following two properties hold:
122 *
123 * 1) Given the snippet:
124 *
125 * { X = 0; Y = 0; }
126 *
127 * CPU0 CPU1
128 *
129 * WRITE_ONCE(X, 1); WRITE_ONCE(Y, 1);
130 * spin_lock(S); smp_mb();
131 * smp_mb__after_spinlock(); r1 = READ_ONCE(X);
132 * r0 = READ_ONCE(Y);
133 * spin_unlock(S);
134 *
135 * it is forbidden that CPU0 does not observe CPU1's store to Y (r0 = 0)
136 * and CPU1 does not observe CPU0's store to X (r1 = 0); see the comments
137 * preceding the call to smp_mb__after_spinlock() in __schedule() and in
138 * try_to_wake_up().
139 *
140 * 2) Given the snippet:
141 *
142 * { X = 0; Y = 0; }
143 *
144 * CPU0 CPU1 CPU2
145 *
146 * spin_lock(S); spin_lock(S); r1 = READ_ONCE(Y);
147 * WRITE_ONCE(X, 1); smp_mb__after_spinlock(); smp_rmb();
148 * spin_unlock(S); r0 = READ_ONCE(X); r2 = READ_ONCE(X);
149 * WRITE_ONCE(Y, 1);
150 * spin_unlock(S);
151 *
152 * it is forbidden that CPU0's critical section executes before CPU1's
153 * critical section (r0 = 1), CPU2 observes CPU1's store to Y (r1 = 1)
154 * and CPU2 does not observe CPU0's store to X (r2 = 0); see the comments
155 * preceding the calls to smp_rmb() in try_to_wake_up() for similar
156 * snippets but "projected" onto two CPUs.
157 *
158 * Property (2) upgrades the lock to an RCsc lock.
159 *
160 * Since most load-store architectures implement ACQUIRE with an smp_mb() after
161 * the LL/SC loop, they need no further barriers. Similarly all our TSO
162 * architectures imply an smp_mb() for each atomic instruction and equally don't
163 * need more.
164 *
165 * Architectures that can implement ACQUIRE better need to take care.
166 */
167 #ifndef smp_mb__after_spinlock
168 #define smp_mb__after_spinlock() do { } while (0)
169 #endif
170
171 #ifdef CONFIG_DEBUG_SPINLOCK
172 extern void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock);
173 #define do_raw_spin_lock_flags(lock, flags) do_raw_spin_lock(lock)
174 extern int do_raw_spin_trylock(raw_spinlock_t *lock);
175 extern void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock);
176 #else
177 static inline void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock)
178 {
179 __acquire(lock);
180 arch_spin_lock(&lock->raw_lock);
181 }
182
183 #ifndef arch_spin_lock_flags
184 #define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
185 #endif
186
187 static inline void
188 do_raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long *flags) __acquires(lock)
189 {
190 __acquire(lock);
191 arch_spin_lock_flags(&lock->raw_lock, *flags);
192 }
193
194 static inline int do_raw_spin_trylock(raw_spinlock_t *lock)
195 {
196 return arch_spin_trylock(&(lock)->raw_lock);
197 }
198
199 static inline void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock)
200 {
201 arch_spin_unlock(&lock->raw_lock);
202 __release(lock);
203 }
204 #endif
205
206 /*
207 * Define the various spin_lock methods. Note we define these
208 * regardless of whether CONFIG_SMP or CONFIG_PREEMPT are set. The
209 * various methods are defined as nops in the case they are not
210 * required.
211 */
212 #define raw_spin_trylock(lock) __cond_lock(lock, _raw_spin_trylock(lock))
213
214 #define raw_spin_lock(lock) _raw_spin_lock(lock)
215
216 #ifdef CONFIG_DEBUG_LOCK_ALLOC
217 # define raw_spin_lock_nested(lock, subclass) \
218 _raw_spin_lock_nested(lock, subclass)
219
220 # define raw_spin_lock_nest_lock(lock, nest_lock) \
221 do { \
222 typecheck(struct lockdep_map *, &(nest_lock)->dep_map);\
223 _raw_spin_lock_nest_lock(lock, &(nest_lock)->dep_map); \
224 } while (0)
225 #else
226 /*
227 * Always evaluate the 'subclass' argument to avoid that the compiler
228 * warns about set-but-not-used variables when building with
229 * CONFIG_DEBUG_LOCK_ALLOC=n and with W=1.
230 */
231 # define raw_spin_lock_nested(lock, subclass) \
232 _raw_spin_lock(((void)(subclass), (lock)))
233 # define raw_spin_lock_nest_lock(lock, nest_lock) _raw_spin_lock(lock)
234 #endif
235
236 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
237
238 #define raw_spin_lock_irqsave(lock, flags) \
239 do { \
240 typecheck(unsigned long, flags); \
241 flags = _raw_spin_lock_irqsave(lock); \
242 } while (0)
243
244 #ifdef CONFIG_DEBUG_LOCK_ALLOC
245 #define raw_spin_lock_irqsave_nested(lock, flags, subclass) \
246 do { \
247 typecheck(unsigned long, flags); \
248 flags = _raw_spin_lock_irqsave_nested(lock, subclass); \
249 } while (0)
250 #else
251 #define raw_spin_lock_irqsave_nested(lock, flags, subclass) \
252 do { \
253 typecheck(unsigned long, flags); \
254 flags = _raw_spin_lock_irqsave(lock); \
255 } while (0)
256 #endif
257
258 #else
259
260 #define raw_spin_lock_irqsave(lock, flags) \
261 do { \
262 typecheck(unsigned long, flags); \
263 _raw_spin_lock_irqsave(lock, flags); \
264 } while (0)
265
266 #define raw_spin_lock_irqsave_nested(lock, flags, subclass) \
267 raw_spin_lock_irqsave(lock, flags)
268
269 #endif
270
271 #define raw_spin_lock_irq(lock) _raw_spin_lock_irq(lock)
272 #define raw_spin_lock_bh(lock) _raw_spin_lock_bh(lock)
273 #define raw_spin_unlock(lock) _raw_spin_unlock(lock)
274 #define raw_spin_unlock_irq(lock) _raw_spin_unlock_irq(lock)
275
276 #define raw_spin_unlock_irqrestore(lock, flags) \
277 do { \
278 typecheck(unsigned long, flags); \
279 _raw_spin_unlock_irqrestore(lock, flags); \
280 } while (0)
281 #define raw_spin_unlock_bh(lock) _raw_spin_unlock_bh(lock)
282
283 #define raw_spin_trylock_bh(lock) \
284 __cond_lock(lock, _raw_spin_trylock_bh(lock))
285
286 #define raw_spin_trylock_irq(lock) \
287 ({ \
288 local_irq_disable(); \
289 raw_spin_trylock(lock) ? \
290 1 : ({ local_irq_enable(); 0; }); \
291 })
292
293 #define raw_spin_trylock_irqsave(lock, flags) \
294 ({ \
295 local_irq_save(flags); \
296 raw_spin_trylock(lock) ? \
297 1 : ({ local_irq_restore(flags); 0; }); \
298 })
299
300 /* Include rwlock functions */
301 #include <linux/rwlock.h>
302
303 /*
304 * Pull the _spin_*()/_read_*()/_write_*() functions/declarations:
305 */
306 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
307 # include <linux/spinlock_api_smp.h>
308 #else
309 # include <linux/spinlock_api_up.h>
310 #endif
311
312 /*
313 * Map the spin_lock functions to the raw variants for PREEMPT_RT=n
314 */
315
316 static __always_inline raw_spinlock_t *spinlock_check(spinlock_t *lock)
317 {
318 return &lock->rlock;
319 }
320
321 #define spin_lock_init(_lock) \
322 do { \
323 spinlock_check(_lock); \
324 raw_spin_lock_init(&(_lock)->rlock); \
325 } while (0)
326
327 static __always_inline void spin_lock(spinlock_t *lock)
328 {
329 raw_spin_lock(&lock->rlock);
330 }
331
332 static __always_inline void spin_lock_bh(spinlock_t *lock)
333 {
334 raw_spin_lock_bh(&lock->rlock);
335 }
336
337 static __always_inline int spin_trylock(spinlock_t *lock)
338 {
339 return raw_spin_trylock(&lock->rlock);
340 }
341
342 #define spin_lock_nested(lock, subclass) \
343 do { \
344 raw_spin_lock_nested(spinlock_check(lock), subclass); \
345 } while (0)
346
347 #define spin_lock_nest_lock(lock, nest_lock) \
348 do { \
349 raw_spin_lock_nest_lock(spinlock_check(lock), nest_lock); \
350 } while (0)
351
352 static __always_inline void spin_lock_irq(spinlock_t *lock)
353 {
354 raw_spin_lock_irq(&lock->rlock);
355 }
356
357 #define spin_lock_irqsave(lock, flags) \
358 do { \
359 raw_spin_lock_irqsave(spinlock_check(lock), flags); \
360 } while (0)
361
362 #define spin_lock_irqsave_nested(lock, flags, subclass) \
363 do { \
364 raw_spin_lock_irqsave_nested(spinlock_check(lock), flags, subclass); \
365 } while (0)
366
367 static __always_inline void spin_unlock(spinlock_t *lock)
368 {
369 raw_spin_unlock(&lock->rlock);
370 }
371
372 static __always_inline void spin_unlock_bh(spinlock_t *lock)
373 {
374 raw_spin_unlock_bh(&lock->rlock);
375 }
376
377 static __always_inline void spin_unlock_irq(spinlock_t *lock)
378 {
379 raw_spin_unlock_irq(&lock->rlock);
380 }
381
382 static __always_inline void spin_unlock_irqrestore(spinlock_t *lock, unsigned long flags)
383 {
384 raw_spin_unlock_irqrestore(&lock->rlock, flags);
385 }
386
387 static __always_inline int spin_trylock_bh(spinlock_t *lock)
388 {
389 return raw_spin_trylock_bh(&lock->rlock);
390 }
391
392 static __always_inline int spin_trylock_irq(spinlock_t *lock)
393 {
394 return raw_spin_trylock_irq(&lock->rlock);
395 }
396
397 #define spin_trylock_irqsave(lock, flags) \
398 ({ \
399 raw_spin_trylock_irqsave(spinlock_check(lock), flags); \
400 })
401
402 /**
403 * spin_is_locked() - Check whether a spinlock is locked.
404 * @lock: Pointer to the spinlock.
405 *
406 * This function is NOT required to provide any memory ordering
407 * guarantees; it could be used for debugging purposes or, when
408 * additional synchronization is needed, accompanied with other
409 * constructs (memory barriers) enforcing the synchronization.
410 *
411 * Returns: 1 if @lock is locked, 0 otherwise.
412 *
413 * Note that the function only tells you that the spinlock is
414 * seen to be locked, not that it is locked on your CPU.
415 *
416 * Further, on CONFIG_SMP=n builds with CONFIG_DEBUG_SPINLOCK=n,
417 * the return value is always 0 (see include/linux/spinlock_up.h).
418 * Therefore you should not rely heavily on the return value.
419 */
420 static __always_inline int spin_is_locked(spinlock_t *lock)
421 {
422 return raw_spin_is_locked(&lock->rlock);
423 }
424
425 static __always_inline int spin_is_contended(spinlock_t *lock)
426 {
427 return raw_spin_is_contended(&lock->rlock);
428 }
429
430 #define assert_spin_locked(lock) assert_raw_spin_locked(&(lock)->rlock)
431
432 /*
433 * Pull the atomic_t declaration:
434 * (asm-mips/atomic.h needs above definitions)
435 */
436 #include <linux/atomic.h>
437 /**
438 * atomic_dec_and_lock - lock on reaching reference count zero
439 * @atomic: the atomic counter
440 * @lock: the spinlock in question
441 *
442 * Decrements @atomic by 1. If the result is 0, returns true and locks
443 * @lock. Returns false for all other cases.
444 */
445 extern int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock);
446 #define atomic_dec_and_lock(atomic, lock) \
447 __cond_lock(lock, _atomic_dec_and_lock(atomic, lock))
448
449 extern int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock,
450 unsigned long *flags);
451 #define atomic_dec_and_lock_irqsave(atomic, lock, flags) \
452 __cond_lock(lock, _atomic_dec_and_lock_irqsave(atomic, lock, &(flags)))
453
454 int __alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *lock_mask,
455 size_t max_size, unsigned int cpu_mult,
456 gfp_t gfp, const char *name,
457 struct lock_class_key *key);
458
459 #define alloc_bucket_spinlocks(locks, lock_mask, max_size, cpu_mult, gfp) \
460 ({ \
461 static struct lock_class_key key; \
462 int ret; \
463 \
464 ret = __alloc_bucket_spinlocks(locks, lock_mask, max_size, \
465 cpu_mult, gfp, #locks, &key); \
466 ret; \
467 })
468
469 void free_bucket_spinlocks(spinlock_t *locks);
470
471 #endif /* __LINUX_SPINLOCK_H */
472
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