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