spinlock.h

  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)					\
105do {									\
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
184static 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
191static 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
201static 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
324static __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)					\
332do {								\
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)			\
342do {						\
343	spinlock_check(_lock);			\
344	*(_lock) = __SPIN_LOCK_UNLOCKED(_lock);	\
345} while (0)
346
347#endif
348
349static __always_inline void spin_lock(spinlock_t *lock)
350{
351	raw_spin_lock(&lock->rlock);
352}
353
354static __always_inline void spin_lock_bh(spinlock_t *lock)
355{
356	raw_spin_lock_bh(&lock->rlock);
357}
358
359static __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)			\
365do {								\
366	raw_spin_lock_nested(spinlock_check(lock), subclass);	\
367} while (0)
368
369#define spin_lock_nest_lock(lock, nest_lock)				\
370do {									\
371	raw_spin_lock_nest_lock(spinlock_check(lock), nest_lock);	\
372} while (0)
373
374static __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)				\
380do {								\
381	raw_spin_lock_irqsave(spinlock_check(lock), flags);	\
382} while (0)
383
384#define spin_lock_irqsave_nested(lock, flags, subclass)			\
385do {									\
386	raw_spin_lock_irqsave_nested(spinlock_check(lock), flags, subclass); \
387} while (0)
388
389static __always_inline void spin_unlock(spinlock_t *lock)
390{
391	raw_spin_unlock(&lock->rlock);
392}
393
394static __always_inline void spin_unlock_bh(spinlock_t *lock)
395{
396	raw_spin_unlock_bh(&lock->rlock);
397}
398
399static __always_inline void spin_unlock_irq(spinlock_t *lock)
400{
401	raw_spin_unlock_irq(&lock->rlock);
402}
403
404static __always_inline void spin_unlock_irqrestore(spinlock_t *lock, unsigned long flags)
405{
406	raw_spin_unlock_irqrestore(&lock->rlock, flags);
407}
408
409static __always_inline int spin_trylock_bh(spinlock_t *lock)
410{
411	return raw_spin_trylock_bh(&lock->rlock);
412}
413
414static __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 */
442static __always_inline int spin_is_locked(spinlock_t *lock)
443{
444	return raw_spin_is_locked(&lock->rlock);
445}
446
447static __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 * Does a critical section need to be broken due to another
460 * task waiting?: (technically does not depend on CONFIG_PREEMPTION,
461 * but a general need for low latency)
462 */
463static inline int spin_needbreak(spinlock_t *lock)
464{
465	if (!preempt_model_preemptible())
466		return 0;
467
468	return spin_is_contended(lock);
469}
470
471/*
472 * Check if a rwlock is contended.
473 * Returns non-zero if there is another task waiting on the rwlock.
474 * Returns zero if the lock is not contended or the system / underlying
475 * rwlock implementation does not support contention detection.
476 * Technically does not depend on CONFIG_PREEMPTION, but a general need
477 * for low latency.
478 */
479static inline int rwlock_needbreak(rwlock_t *lock)
480{
481	if (!preempt_model_preemptible())
482		return 0;
483
484	return rwlock_is_contended(lock);
485}
486
487/*
488 * Pull the atomic_t declaration:
489 * (asm-mips/atomic.h needs above definitions)
490 */
491#include <linux/atomic.h>
492/**
493 * atomic_dec_and_lock - lock on reaching reference count zero
494 * @atomic: the atomic counter
495 * @lock: the spinlock in question
496 *
497 * Decrements @atomic by 1.  If the result is 0, returns true and locks
498 * @lock.  Returns false for all other cases.
499 */
500extern int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock);
501#define atomic_dec_and_lock(atomic, lock) \
502		__cond_lock(lock, _atomic_dec_and_lock(atomic, lock))
503
504extern int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock,
505					unsigned long *flags);
506#define atomic_dec_and_lock_irqsave(atomic, lock, flags) \
507		__cond_lock(lock, _atomic_dec_and_lock_irqsave(atomic, lock, &(flags)))
508
509extern int _atomic_dec_and_raw_lock(atomic_t *atomic, raw_spinlock_t *lock);
510#define atomic_dec_and_raw_lock(atomic, lock) \
511		__cond_lock(lock, _atomic_dec_and_raw_lock(atomic, lock))
512
513extern int _atomic_dec_and_raw_lock_irqsave(atomic_t *atomic, raw_spinlock_t *lock,
514					unsigned long *flags);
515#define atomic_dec_and_raw_lock_irqsave(atomic, lock, flags) \
516		__cond_lock(lock, _atomic_dec_and_raw_lock_irqsave(atomic, lock, &(flags)))
517
518int __alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *lock_mask,
519			     size_t max_size, unsigned int cpu_mult,
520			     gfp_t gfp, const char *name,
521			     struct lock_class_key *key);
522
523#define alloc_bucket_spinlocks(locks, lock_mask, max_size, cpu_mult, gfp)    \
524	({								     \
525		static struct lock_class_key key;			     \
526		int ret;						     \
527									     \
528		ret = __alloc_bucket_spinlocks(locks, lock_mask, max_size,   \
529					       cpu_mult, gfp, #locks, &key); \
530		ret;							     \
531	})
532
533void free_bucket_spinlocks(spinlock_t *locks);
534
535DEFINE_LOCK_GUARD_1(raw_spinlock, raw_spinlock_t,
536		    raw_spin_lock(_T->lock),
537		    raw_spin_unlock(_T->lock))
538
539DEFINE_LOCK_GUARD_1_COND(raw_spinlock, _try, raw_spin_trylock(_T->lock))
540
541DEFINE_LOCK_GUARD_1(raw_spinlock_nested, raw_spinlock_t,
542		    raw_spin_lock_nested(_T->lock, SINGLE_DEPTH_NESTING),
543		    raw_spin_unlock(_T->lock))
544
545DEFINE_LOCK_GUARD_1(raw_spinlock_irq, raw_spinlock_t,
546		    raw_spin_lock_irq(_T->lock),
547		    raw_spin_unlock_irq(_T->lock))
548
549DEFINE_LOCK_GUARD_1_COND(raw_spinlock_irq, _try, raw_spin_trylock_irq(_T->lock))
550
551DEFINE_LOCK_GUARD_1(raw_spinlock_bh, raw_spinlock_t,
552		    raw_spin_lock_bh(_T->lock),
553		    raw_spin_unlock_bh(_T->lock))
554
555DEFINE_LOCK_GUARD_1_COND(raw_spinlock_bh, _try, raw_spin_trylock_bh(_T->lock))
556
557DEFINE_LOCK_GUARD_1(raw_spinlock_irqsave, raw_spinlock_t,
558		    raw_spin_lock_irqsave(_T->lock, _T->flags),
559		    raw_spin_unlock_irqrestore(_T->lock, _T->flags),
560		    unsigned long flags)
561
562DEFINE_LOCK_GUARD_1_COND(raw_spinlock_irqsave, _try,
563			 raw_spin_trylock_irqsave(_T->lock, _T->flags))
564
565DEFINE_LOCK_GUARD_1(spinlock, spinlock_t,
566		    spin_lock(_T->lock),
567		    spin_unlock(_T->lock))
568
569DEFINE_LOCK_GUARD_1_COND(spinlock, _try, spin_trylock(_T->lock))
570
571DEFINE_LOCK_GUARD_1(spinlock_irq, spinlock_t,
572		    spin_lock_irq(_T->lock),
573		    spin_unlock_irq(_T->lock))
574
575DEFINE_LOCK_GUARD_1_COND(spinlock_irq, _try,
576			 spin_trylock_irq(_T->lock))
577
578DEFINE_LOCK_GUARD_1(spinlock_bh, spinlock_t,
579		    spin_lock_bh(_T->lock),
580		    spin_unlock_bh(_T->lock))
581
582DEFINE_LOCK_GUARD_1_COND(spinlock_bh, _try,
583			 spin_trylock_bh(_T->lock))
584
585DEFINE_LOCK_GUARD_1(spinlock_irqsave, spinlock_t,
586		    spin_lock_irqsave(_T->lock, _T->flags),
587		    spin_unlock_irqrestore(_T->lock, _T->flags),
588		    unsigned long flags)
589
590DEFINE_LOCK_GUARD_1_COND(spinlock_irqsave, _try,
591			 spin_trylock_irqsave(_T->lock, _T->flags))
592
593DEFINE_LOCK_GUARD_1(read_lock, rwlock_t,
594		    read_lock(_T->lock),
595		    read_unlock(_T->lock))
596
597DEFINE_LOCK_GUARD_1(read_lock_irq, rwlock_t,
598		    read_lock_irq(_T->lock),
599		    read_unlock_irq(_T->lock))
600
601DEFINE_LOCK_GUARD_1(read_lock_irqsave, rwlock_t,
602		    read_lock_irqsave(_T->lock, _T->flags),
603		    read_unlock_irqrestore(_T->lock, _T->flags),
604		    unsigned long flags)
605
606DEFINE_LOCK_GUARD_1(write_lock, rwlock_t,
607		    write_lock(_T->lock),
608		    write_unlock(_T->lock))
609
610DEFINE_LOCK_GUARD_1(write_lock_irq, rwlock_t,
611		    write_lock_irq(_T->lock),
612		    write_unlock_irq(_T->lock))
613
614DEFINE_LOCK_GUARD_1(write_lock_irqsave, rwlock_t,
615		    write_lock_irqsave(_T->lock, _T->flags),
616		    write_unlock_irqrestore(_T->lock, _T->flags),
617		    unsigned long flags)
618
619#undef __LINUX_INSIDE_SPINLOCK_H
620#endif /* __LINUX_SPINLOCK_H */