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

source code of linux/include/linux/spinlock.h