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.h:
16 * defines the generic type and initializers
18 * asm/spinlock.h: contains the arch_spin_*()/etc. lowlevel
19 * implementations, mostly inline assembly code
21 * (also included on UP-debug builds:)
23 * linux/spinlock_api_smp.h:
24 * contains the prototypes for the _spin_*() APIs.
26 * linux/spinlock.h: builds the final spin_*() APIs.
30 * linux/spinlock_type_up.h:
31 * contains the generic, simplified UP spinlock type.
32 * (which is an empty structure on non-debug builds)
34 * linux/spinlock_types.h:
35 * defines the generic type and initializers
37 * linux/spinlock_up.h:
38 * contains the arch_spin_*()/etc. version of UP
39 * builds. (which are NOPs on non-debug, non-preempt
42 * (included on UP-non-debug builds:)
44 * linux/spinlock_api_up.h:
45 * builds the _spin_*() APIs.
47 * linux/spinlock.h: builds the final spin_*() APIs.
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 #include <asm/mmiowb.h>
64 * Must define these before including other files, inline functions need them
66 #define LOCK_SECTION_NAME ".text..lock."KBUILD_BASENAME
68 #define LOCK_SECTION_START(extra) \
71 ".ifndef " LOCK_SECTION_NAME "\n\t" \
72 LOCK_SECTION_NAME ":\n\t" \
75 #define LOCK_SECTION_END \
78 #define __lockfunc __attribute__((section(".spinlock.text")))
81 * Pull the arch_spinlock_t and arch_rwlock_t definitions:
83 #include <linux/spinlock_types.h>
86 * Pull the arch_spin*() functions/declarations (UP-nondebug doesn't need them):
89 # include <asm/spinlock.h>
91 # include <linux/spinlock_up.h>
94 #ifdef CONFIG_DEBUG_SPINLOCK
95 extern void __raw_spin_lock_init(raw_spinlock_t *lock, const char *name,
96 struct lock_class_key *key, short inner);
98 # define raw_spin_lock_init(lock) \
100 static struct lock_class_key __key; \
102 __raw_spin_lock_init((lock), #lock, &__key, LD_WAIT_SPIN); \
106 # define raw_spin_lock_init(lock) \
107 do { *(lock) = __RAW_SPIN_LOCK_UNLOCKED(lock); } while (0)
110 #define raw_spin_is_locked(lock) arch_spin_is_locked(&(lock)->raw_lock)
112 #ifdef arch_spin_is_contended
113 #define raw_spin_is_contended(lock) arch_spin_is_contended(&(lock)->raw_lock)
115 #define raw_spin_is_contended(lock) (((void)(lock), 0))
116 #endif /*arch_spin_is_contended*/
119 * smp_mb__after_spinlock() provides the equivalent of a full memory barrier
120 * between program-order earlier lock acquisitions and program-order later
123 * This guarantees that the following two properties hold:
125 * 1) Given the snippet:
131 * WRITE_ONCE(X, 1); WRITE_ONCE(Y, 1);
132 * spin_lock(S); smp_mb();
133 * smp_mb__after_spinlock(); r1 = READ_ONCE(X);
137 * it is forbidden that CPU0 does not observe CPU1's store to Y (r0 = 0)
138 * and CPU1 does not observe CPU0's store to X (r1 = 0); see the comments
139 * preceding the call to smp_mb__after_spinlock() in __schedule() and in
142 * 2) Given the snippet:
148 * spin_lock(S); spin_lock(S); r1 = READ_ONCE(Y);
149 * WRITE_ONCE(X, 1); smp_mb__after_spinlock(); smp_rmb();
150 * spin_unlock(S); r0 = READ_ONCE(X); r2 = READ_ONCE(X);
154 * it is forbidden that CPU0's critical section executes before CPU1's
155 * critical section (r0 = 1), CPU2 observes CPU1's store to Y (r1 = 1)
156 * and CPU2 does not observe CPU0's store to X (r2 = 0); see the comments
157 * preceding the calls to smp_rmb() in try_to_wake_up() for similar
158 * snippets but "projected" onto two CPUs.
160 * Property (2) upgrades the lock to an RCsc lock.
162 * Since most load-store architectures implement ACQUIRE with an smp_mb() after
163 * the LL/SC loop, they need no further barriers. Similarly all our TSO
164 * architectures imply an smp_mb() for each atomic instruction and equally don't
167 * Architectures that can implement ACQUIRE better need to take care.
169 #ifndef smp_mb__after_spinlock
170 #define smp_mb__after_spinlock() do { } while (0)
173 #ifdef CONFIG_DEBUG_SPINLOCK
174 extern void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock);
175 #define do_raw_spin_lock_flags(lock, flags) do_raw_spin_lock(lock)
176 extern int do_raw_spin_trylock(raw_spinlock_t *lock);
177 extern void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock);
179 static inline void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock)
182 arch_spin_lock(&lock->raw_lock);
186 #ifndef arch_spin_lock_flags
187 #define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
191 do_raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long *flags) __acquires(lock)
194 arch_spin_lock_flags(&lock->raw_lock, *flags);
198 static inline int do_raw_spin_trylock(raw_spinlock_t *lock)
200 int ret = arch_spin_trylock(&(lock)->raw_lock);
208 static inline void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock)
210 mmiowb_spin_unlock();
211 arch_spin_unlock(&lock->raw_lock);
217 * Define the various spin_lock methods. Note we define these
218 * regardless of whether CONFIG_SMP or CONFIG_PREEMPTION are set. The
219 * various methods are defined as nops in the case they are not
222 #define raw_spin_trylock(lock) __cond_lock(lock, _raw_spin_trylock(lock))
224 #define raw_spin_lock(lock) _raw_spin_lock(lock)
226 #ifdef CONFIG_DEBUG_LOCK_ALLOC
227 # define raw_spin_lock_nested(lock, subclass) \
228 _raw_spin_lock_nested(lock, subclass)
230 # define raw_spin_lock_nest_lock(lock, nest_lock) \
232 typecheck(struct lockdep_map *, &(nest_lock)->dep_map);\
233 _raw_spin_lock_nest_lock(lock, &(nest_lock)->dep_map); \
237 * Always evaluate the 'subclass' argument to avoid that the compiler
238 * warns about set-but-not-used variables when building with
239 * CONFIG_DEBUG_LOCK_ALLOC=n and with W=1.
241 # define raw_spin_lock_nested(lock, subclass) \
242 _raw_spin_lock(((void)(subclass), (lock)))
243 # define raw_spin_lock_nest_lock(lock, nest_lock) _raw_spin_lock(lock)
246 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
248 #define raw_spin_lock_irqsave(lock, flags) \
250 typecheck(unsigned long, flags); \
251 flags = _raw_spin_lock_irqsave(lock); \
254 #ifdef CONFIG_DEBUG_LOCK_ALLOC
255 #define raw_spin_lock_irqsave_nested(lock, flags, subclass) \
257 typecheck(unsigned long, flags); \
258 flags = _raw_spin_lock_irqsave_nested(lock, subclass); \
261 #define raw_spin_lock_irqsave_nested(lock, flags, subclass) \
263 typecheck(unsigned long, flags); \
264 flags = _raw_spin_lock_irqsave(lock); \
270 #define raw_spin_lock_irqsave(lock, flags) \
272 typecheck(unsigned long, flags); \
273 _raw_spin_lock_irqsave(lock, flags); \
276 #define raw_spin_lock_irqsave_nested(lock, flags, subclass) \
277 raw_spin_lock_irqsave(lock, flags)
281 #define raw_spin_lock_irq(lock) _raw_spin_lock_irq(lock)
282 #define raw_spin_lock_bh(lock) _raw_spin_lock_bh(lock)
283 #define raw_spin_unlock(lock) _raw_spin_unlock(lock)
284 #define raw_spin_unlock_irq(lock) _raw_spin_unlock_irq(lock)
286 #define raw_spin_unlock_irqrestore(lock, flags) \
288 typecheck(unsigned long, flags); \
289 _raw_spin_unlock_irqrestore(lock, flags); \
291 #define raw_spin_unlock_bh(lock) _raw_spin_unlock_bh(lock)
293 #define raw_spin_trylock_bh(lock) \
294 __cond_lock(lock, _raw_spin_trylock_bh(lock))
296 #define raw_spin_trylock_irq(lock) \
298 local_irq_disable(); \
299 raw_spin_trylock(lock) ? \
300 1 : ({ local_irq_enable(); 0; }); \
303 #define raw_spin_trylock_irqsave(lock, flags) \
305 local_irq_save(flags); \
306 raw_spin_trylock(lock) ? \
307 1 : ({ local_irq_restore(flags); 0; }); \
310 /* Include rwlock functions */
311 #include <linux/rwlock.h>
314 * Pull the _spin_*()/_read_*()/_write_*() functions/declarations:
316 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
317 # include <linux/spinlock_api_smp.h>
319 # include <linux/spinlock_api_up.h>
323 * Map the spin_lock functions to the raw variants for PREEMPT_RT=n
326 static __always_inline raw_spinlock_t *spinlock_check(spinlock_t *lock)
331 #ifdef CONFIG_DEBUG_SPINLOCK
333 # define spin_lock_init(lock) \
335 static struct lock_class_key __key; \
337 __raw_spin_lock_init(spinlock_check(lock), \
338 #lock, &__key, LD_WAIT_CONFIG); \
343 # define spin_lock_init(_lock) \
345 spinlock_check(_lock); \
346 *(_lock) = __SPIN_LOCK_UNLOCKED(_lock); \
351 static __always_inline void spin_lock(spinlock_t *lock)
353 raw_spin_lock(&lock->rlock);
356 static __always_inline void spin_lock_bh(spinlock_t *lock)
358 raw_spin_lock_bh(&lock->rlock);
361 static __always_inline int spin_trylock(spinlock_t *lock)
363 return raw_spin_trylock(&lock->rlock);
366 #define spin_lock_nested(lock, subclass) \
368 raw_spin_lock_nested(spinlock_check(lock), subclass); \
371 #define spin_lock_nest_lock(lock, nest_lock) \
373 raw_spin_lock_nest_lock(spinlock_check(lock), nest_lock); \
376 static __always_inline void spin_lock_irq(spinlock_t *lock)
378 raw_spin_lock_irq(&lock->rlock);
381 #define spin_lock_irqsave(lock, flags) \
383 raw_spin_lock_irqsave(spinlock_check(lock), flags); \
386 #define spin_lock_irqsave_nested(lock, flags, subclass) \
388 raw_spin_lock_irqsave_nested(spinlock_check(lock), flags, subclass); \
391 static __always_inline void spin_unlock(spinlock_t *lock)
393 raw_spin_unlock(&lock->rlock);
396 static __always_inline void spin_unlock_bh(spinlock_t *lock)
398 raw_spin_unlock_bh(&lock->rlock);
401 static __always_inline void spin_unlock_irq(spinlock_t *lock)
403 raw_spin_unlock_irq(&lock->rlock);
406 static __always_inline void spin_unlock_irqrestore(spinlock_t *lock, unsigned long flags)
408 raw_spin_unlock_irqrestore(&lock->rlock, flags);
411 static __always_inline int spin_trylock_bh(spinlock_t *lock)
413 return raw_spin_trylock_bh(&lock->rlock);
416 static __always_inline int spin_trylock_irq(spinlock_t *lock)
418 return raw_spin_trylock_irq(&lock->rlock);
421 #define spin_trylock_irqsave(lock, flags) \
423 raw_spin_trylock_irqsave(spinlock_check(lock), flags); \
427 * spin_is_locked() - Check whether a spinlock is locked.
428 * @lock: Pointer to the spinlock.
430 * This function is NOT required to provide any memory ordering
431 * guarantees; it could be used for debugging purposes or, when
432 * additional synchronization is needed, accompanied with other
433 * constructs (memory barriers) enforcing the synchronization.
435 * Returns: 1 if @lock is locked, 0 otherwise.
437 * Note that the function only tells you that the spinlock is
438 * seen to be locked, not that it is locked on your CPU.
440 * Further, on CONFIG_SMP=n builds with CONFIG_DEBUG_SPINLOCK=n,
441 * the return value is always 0 (see include/linux/spinlock_up.h).
442 * Therefore you should not rely heavily on the return value.
444 static __always_inline int spin_is_locked(spinlock_t *lock)
446 return raw_spin_is_locked(&lock->rlock);
449 static __always_inline int spin_is_contended(spinlock_t *lock)
451 return raw_spin_is_contended(&lock->rlock);
454 #define assert_spin_locked(lock) assert_raw_spin_locked(&(lock)->rlock)
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 */