1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __LINUX_SPINLOCK_H
3 #define __LINUX_SPINLOCK_H
6 * include/linux/spinlock.h - generic spinlock/rwlock declarations
8 * here's the role of the various spinlock/rwlock related include files:
12 * asm/spinlock_types.h: contains the arch_spinlock_t/arch_rwlock_t and the
15 * linux/spinlock_types_raw:
16 * The raw types and initializers
17 * linux/spinlock_types.h:
18 * defines the generic type and initializers
20 * asm/spinlock.h: contains the arch_spin_*()/etc. lowlevel
21 * implementations, mostly inline assembly code
23 * (also included on UP-debug builds:)
25 * linux/spinlock_api_smp.h:
26 * contains the prototypes for the _spin_*() APIs.
28 * linux/spinlock.h: builds the final spin_*() APIs.
32 * linux/spinlock_type_up.h:
33 * contains the generic, simplified UP spinlock type.
34 * (which is an empty structure on non-debug builds)
36 * linux/spinlock_types_raw:
37 * The raw RT types and initializers
38 * linux/spinlock_types.h:
39 * defines the generic type and initializers
41 * linux/spinlock_up.h:
42 * contains the arch_spin_*()/etc. version of UP
43 * builds. (which are NOPs on non-debug, non-preempt
46 * (included on UP-non-debug builds:)
48 * linux/spinlock_api_up.h:
49 * builds the _spin_*() APIs.
51 * linux/spinlock.h: builds the final spin_*() APIs.
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>
68 * Must define these before including other files, inline functions need them
70 #define LOCK_SECTION_NAME ".text..lock."KBUILD_BASENAME
72 #define LOCK_SECTION_START(extra) \
75 ".ifndef " LOCK_SECTION_NAME "\n\t" \
76 LOCK_SECTION_NAME ":\n\t" \
79 #define LOCK_SECTION_END \
82 #define __lockfunc __section(".spinlock.text")
85 * Pull the arch_spinlock_t and arch_rwlock_t definitions:
87 #include <linux/spinlock_types.h>
90 * Pull the arch_spin*() functions/declarations (UP-nondebug doesn't need them):
93 # include <asm/spinlock.h>
95 # include <linux/spinlock_up.h>
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);
102 # define raw_spin_lock_init(lock) \
104 static struct lock_class_key __key; \
106 __raw_spin_lock_init((lock), #lock, &__key, LD_WAIT_SPIN); \
110 # define raw_spin_lock_init(lock) \
111 do { *(lock) = __RAW_SPIN_LOCK_UNLOCKED(lock); } while (0)
114 #define raw_spin_is_locked(lock) arch_spin_is_locked(&(lock)->raw_lock)
116 #ifdef arch_spin_is_contended
117 #define raw_spin_is_contended(lock) arch_spin_is_contended(&(lock)->raw_lock)
119 #define raw_spin_is_contended(lock) (((void)(lock), 0))
120 #endif /*arch_spin_is_contended*/
123 * smp_mb__after_spinlock() provides the equivalent of a full memory barrier
124 * between program-order earlier lock acquisitions and program-order later
127 * This guarantees that the following two properties hold:
129 * 1) Given the snippet:
135 * WRITE_ONCE(X, 1); WRITE_ONCE(Y, 1);
136 * spin_lock(S); smp_mb();
137 * smp_mb__after_spinlock(); r1 = READ_ONCE(X);
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
146 * 2) Given the snippet:
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);
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.
164 * Property (2) upgrades the lock to an RCsc lock.
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
171 * Architectures that can implement ACQUIRE better need to take care.
173 #ifndef smp_mb__after_spinlock
174 #define smp_mb__after_spinlock() kcsan_mb()
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);
182 static inline void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock)
185 arch_spin_lock(&lock->raw_lock);
189 static inline int do_raw_spin_trylock(raw_spinlock_t *lock)
191 int ret = arch_spin_trylock(&(lock)->raw_lock);
199 static inline void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock)
201 mmiowb_spin_unlock();
202 arch_spin_unlock(&lock->raw_lock);
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
213 #define raw_spin_trylock(lock) __cond_lock(lock, _raw_spin_trylock(lock))
215 #define raw_spin_lock(lock) _raw_spin_lock(lock)
217 #ifdef CONFIG_DEBUG_LOCK_ALLOC
218 # define raw_spin_lock_nested(lock, subclass) \
219 _raw_spin_lock_nested(lock, subclass)
221 # define raw_spin_lock_nest_lock(lock, nest_lock) \
223 typecheck(struct lockdep_map *, &(nest_lock)->dep_map);\
224 _raw_spin_lock_nest_lock(lock, &(nest_lock)->dep_map); \
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.
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)
237 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
239 #define raw_spin_lock_irqsave(lock, flags) \
241 typecheck(unsigned long, flags); \
242 flags = _raw_spin_lock_irqsave(lock); \
245 #ifdef CONFIG_DEBUG_LOCK_ALLOC
246 #define raw_spin_lock_irqsave_nested(lock, flags, subclass) \
248 typecheck(unsigned long, flags); \
249 flags = _raw_spin_lock_irqsave_nested(lock, subclass); \
252 #define raw_spin_lock_irqsave_nested(lock, flags, subclass) \
254 typecheck(unsigned long, flags); \
255 flags = _raw_spin_lock_irqsave(lock); \
261 #define raw_spin_lock_irqsave(lock, flags) \
263 typecheck(unsigned long, flags); \
264 _raw_spin_lock_irqsave(lock, flags); \
267 #define raw_spin_lock_irqsave_nested(lock, flags, subclass) \
268 raw_spin_lock_irqsave(lock, flags)
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)
277 #define raw_spin_unlock_irqrestore(lock, flags) \
279 typecheck(unsigned long, flags); \
280 _raw_spin_unlock_irqrestore(lock, flags); \
282 #define raw_spin_unlock_bh(lock) _raw_spin_unlock_bh(lock)
284 #define raw_spin_trylock_bh(lock) \
285 __cond_lock(lock, _raw_spin_trylock_bh(lock))
287 #define raw_spin_trylock_irq(lock) \
289 local_irq_disable(); \
290 raw_spin_trylock(lock) ? \
291 1 : ({ local_irq_enable(); 0; }); \
294 #define raw_spin_trylock_irqsave(lock, flags) \
296 local_irq_save(flags); \
297 raw_spin_trylock(lock) ? \
298 1 : ({ local_irq_restore(flags); 0; }); \
301 #ifndef CONFIG_PREEMPT_RT
302 /* Include rwlock functions for !RT */
303 #include <linux/rwlock.h>
307 * Pull the _spin_*()/_read_*()/_write_*() functions/declarations:
309 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
310 # include <linux/spinlock_api_smp.h>
312 # include <linux/spinlock_api_up.h>
315 /* Non PREEMPT_RT kernel, map to raw spinlocks: */
316 #ifndef CONFIG_PREEMPT_RT
319 * Map the spin_lock functions to the raw variants for PREEMPT_RT=n
322 static __always_inline raw_spinlock_t *spinlock_check(spinlock_t *lock)
327 #ifdef CONFIG_DEBUG_SPINLOCK
329 # define spin_lock_init(lock) \
331 static struct lock_class_key __key; \
333 __raw_spin_lock_init(spinlock_check(lock), \
334 #lock, &__key, LD_WAIT_CONFIG); \
339 # define spin_lock_init(_lock) \
341 spinlock_check(_lock); \
342 *(_lock) = __SPIN_LOCK_UNLOCKED(_lock); \
347 static __always_inline void spin_lock(spinlock_t *lock)
349 raw_spin_lock(&lock->rlock);
352 static __always_inline void spin_lock_bh(spinlock_t *lock)
354 raw_spin_lock_bh(&lock->rlock);
357 static __always_inline int spin_trylock(spinlock_t *lock)
359 return raw_spin_trylock(&lock->rlock);
362 #define spin_lock_nested(lock, subclass) \
364 raw_spin_lock_nested(spinlock_check(lock), subclass); \
367 #define spin_lock_nest_lock(lock, nest_lock) \
369 raw_spin_lock_nest_lock(spinlock_check(lock), nest_lock); \
372 static __always_inline void spin_lock_irq(spinlock_t *lock)
374 raw_spin_lock_irq(&lock->rlock);
377 #define spin_lock_irqsave(lock, flags) \
379 raw_spin_lock_irqsave(spinlock_check(lock), flags); \
382 #define spin_lock_irqsave_nested(lock, flags, subclass) \
384 raw_spin_lock_irqsave_nested(spinlock_check(lock), flags, subclass); \
387 static __always_inline void spin_unlock(spinlock_t *lock)
389 raw_spin_unlock(&lock->rlock);
392 static __always_inline void spin_unlock_bh(spinlock_t *lock)
394 raw_spin_unlock_bh(&lock->rlock);
397 static __always_inline void spin_unlock_irq(spinlock_t *lock)
399 raw_spin_unlock_irq(&lock->rlock);
402 static __always_inline void spin_unlock_irqrestore(spinlock_t *lock, unsigned long flags)
404 raw_spin_unlock_irqrestore(&lock->rlock, flags);
407 static __always_inline int spin_trylock_bh(spinlock_t *lock)
409 return raw_spin_trylock_bh(&lock->rlock);
412 static __always_inline int spin_trylock_irq(spinlock_t *lock)
414 return raw_spin_trylock_irq(&lock->rlock);
417 #define spin_trylock_irqsave(lock, flags) \
419 raw_spin_trylock_irqsave(spinlock_check(lock), flags); \
423 * spin_is_locked() - Check whether a spinlock is locked.
424 * @lock: Pointer to the spinlock.
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.
431 * Returns: 1 if @lock is locked, 0 otherwise.
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.
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.
440 static __always_inline int spin_is_locked(spinlock_t *lock)
442 return raw_spin_is_locked(&lock->rlock);
445 static __always_inline int spin_is_contended(spinlock_t *lock)
447 return raw_spin_is_contended(&lock->rlock);
450 #define assert_spin_locked(lock) assert_raw_spin_locked(&(lock)->rlock)
452 #else /* !CONFIG_PREEMPT_RT */
453 # include <linux/spinlock_rt.h>
454 #endif /* CONFIG_PREEMPT_RT */
457 * Pull the atomic_t declaration:
458 * (asm-mips/atomic.h needs above definitions)
460 #include <linux/atomic.h>
462 * atomic_dec_and_lock - lock on reaching reference count zero
463 * @atomic: the atomic counter
464 * @lock: the spinlock in question
466 * Decrements @atomic by 1. If the result is 0, returns true and locks
467 * @lock. Returns false for all other cases.
469 extern 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))
473 extern 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)))
478 int __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);
483 #define alloc_bucket_spinlocks(locks, lock_mask, max_size, cpu_mult, gfp) \
485 static struct lock_class_key key; \
488 ret = __alloc_bucket_spinlocks(locks, lock_mask, max_size, \
489 cpu_mult, gfp, #locks, &key); \
493 void free_bucket_spinlocks(spinlock_t *locks);
495 #endif /* __LINUX_SPINLOCK_H */