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/kernel.h>
61 #include <linux/stringify.h>
62 #include <linux/bottom_half.h>
63 #include <linux/lockdep.h>
64 #include <asm/barrier.h>
65 #include <asm/mmiowb.h>
69 * Must define these before including other files, inline functions need them
71 #define LOCK_SECTION_NAME ".text..lock."KBUILD_BASENAME
73 #define LOCK_SECTION_START(extra) \
76 ".ifndef " LOCK_SECTION_NAME "\n\t" \
77 LOCK_SECTION_NAME ":\n\t" \
80 #define LOCK_SECTION_END \
83 #define __lockfunc __section(".spinlock.text")
86 * Pull the arch_spinlock_t and arch_rwlock_t definitions:
88 #include <linux/spinlock_types.h>
91 * Pull the arch_spin*() functions/declarations (UP-nondebug doesn't need them):
94 # include <asm/spinlock.h>
96 # include <linux/spinlock_up.h>
99 #ifdef CONFIG_DEBUG_SPINLOCK
100 extern void __raw_spin_lock_init(raw_spinlock_t
*lock
, const char *name
,
101 struct lock_class_key
*key
, short inner
);
103 # define raw_spin_lock_init(lock) \
105 static struct lock_class_key __key; \
107 __raw_spin_lock_init((lock), #lock, &__key, LD_WAIT_SPIN); \
111 # define raw_spin_lock_init(lock) \
112 do { *(lock) = __RAW_SPIN_LOCK_UNLOCKED(lock); } while (0)
115 #define raw_spin_is_locked(lock) arch_spin_is_locked(&(lock)->raw_lock)
117 #ifdef arch_spin_is_contended
118 #define raw_spin_is_contended(lock) arch_spin_is_contended(&(lock)->raw_lock)
120 #define raw_spin_is_contended(lock) (((void)(lock), 0))
121 #endif /*arch_spin_is_contended*/
124 * smp_mb__after_spinlock() provides the equivalent of a full memory barrier
125 * between program-order earlier lock acquisitions and program-order later
128 * This guarantees that the following two properties hold:
130 * 1) Given the snippet:
136 * WRITE_ONCE(X, 1); WRITE_ONCE(Y, 1);
137 * spin_lock(S); smp_mb();
138 * smp_mb__after_spinlock(); r1 = READ_ONCE(X);
142 * it is forbidden that CPU0 does not observe CPU1's store to Y (r0 = 0)
143 * and CPU1 does not observe CPU0's store to X (r1 = 0); see the comments
144 * preceding the call to smp_mb__after_spinlock() in __schedule() and in
147 * 2) Given the snippet:
153 * spin_lock(S); spin_lock(S); r1 = READ_ONCE(Y);
154 * WRITE_ONCE(X, 1); smp_mb__after_spinlock(); smp_rmb();
155 * spin_unlock(S); r0 = READ_ONCE(X); r2 = READ_ONCE(X);
159 * it is forbidden that CPU0's critical section executes before CPU1's
160 * critical section (r0 = 1), CPU2 observes CPU1's store to Y (r1 = 1)
161 * and CPU2 does not observe CPU0's store to X (r2 = 0); see the comments
162 * preceding the calls to smp_rmb() in try_to_wake_up() for similar
163 * snippets but "projected" onto two CPUs.
165 * Property (2) upgrades the lock to an RCsc lock.
167 * Since most load-store architectures implement ACQUIRE with an smp_mb() after
168 * the LL/SC loop, they need no further barriers. Similarly all our TSO
169 * architectures imply an smp_mb() for each atomic instruction and equally don't
172 * Architectures that can implement ACQUIRE better need to take care.
174 #ifndef smp_mb__after_spinlock
175 #define smp_mb__after_spinlock() do { } while (0)
178 #ifdef CONFIG_DEBUG_SPINLOCK
179 extern void do_raw_spin_lock(raw_spinlock_t
*lock
) __acquires(lock
);
180 #define do_raw_spin_lock_flags(lock, flags) do_raw_spin_lock(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
);
184 static inline void do_raw_spin_lock(raw_spinlock_t
*lock
) __acquires(lock
)
187 arch_spin_lock(&lock
->raw_lock
);
191 #ifndef arch_spin_lock_flags
192 #define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
196 do_raw_spin_lock_flags(raw_spinlock_t
*lock
, unsigned long *flags
) __acquires(lock
)
199 arch_spin_lock_flags(&lock
->raw_lock
, *flags
);
203 static inline int do_raw_spin_trylock(raw_spinlock_t
*lock
)
205 int ret
= arch_spin_trylock(&(lock
)->raw_lock
);
213 static inline void do_raw_spin_unlock(raw_spinlock_t
*lock
) __releases(lock
)
215 mmiowb_spin_unlock();
216 arch_spin_unlock(&lock
->raw_lock
);
222 * Define the various spin_lock methods. Note we define these
223 * regardless of whether CONFIG_SMP or CONFIG_PREEMPTION are set. The
224 * various methods are defined as nops in the case they are not
227 #define raw_spin_trylock(lock) __cond_lock(lock, _raw_spin_trylock(lock))
229 #define raw_spin_lock(lock) _raw_spin_lock(lock)
231 #ifdef CONFIG_DEBUG_LOCK_ALLOC
232 # define raw_spin_lock_nested(lock, subclass) \
233 _raw_spin_lock_nested(lock, subclass)
235 # define raw_spin_lock_nest_lock(lock, nest_lock) \
237 typecheck(struct lockdep_map *, &(nest_lock)->dep_map);\
238 _raw_spin_lock_nest_lock(lock, &(nest_lock)->dep_map); \
242 * Always evaluate the 'subclass' argument to avoid that the compiler
243 * warns about set-but-not-used variables when building with
244 * CONFIG_DEBUG_LOCK_ALLOC=n and with W=1.
246 # define raw_spin_lock_nested(lock, subclass) \
247 _raw_spin_lock(((void)(subclass), (lock)))
248 # define raw_spin_lock_nest_lock(lock, nest_lock) _raw_spin_lock(lock)
251 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
253 #define raw_spin_lock_irqsave(lock, flags) \
255 typecheck(unsigned long, flags); \
256 flags = _raw_spin_lock_irqsave(lock); \
259 #ifdef CONFIG_DEBUG_LOCK_ALLOC
260 #define raw_spin_lock_irqsave_nested(lock, flags, subclass) \
262 typecheck(unsigned long, flags); \
263 flags = _raw_spin_lock_irqsave_nested(lock, subclass); \
266 #define raw_spin_lock_irqsave_nested(lock, flags, subclass) \
268 typecheck(unsigned long, flags); \
269 flags = _raw_spin_lock_irqsave(lock); \
275 #define raw_spin_lock_irqsave(lock, flags) \
277 typecheck(unsigned long, flags); \
278 _raw_spin_lock_irqsave(lock, flags); \
281 #define raw_spin_lock_irqsave_nested(lock, flags, subclass) \
282 raw_spin_lock_irqsave(lock, flags)
286 #define raw_spin_lock_irq(lock) _raw_spin_lock_irq(lock)
287 #define raw_spin_lock_bh(lock) _raw_spin_lock_bh(lock)
288 #define raw_spin_unlock(lock) _raw_spin_unlock(lock)
289 #define raw_spin_unlock_irq(lock) _raw_spin_unlock_irq(lock)
291 #define raw_spin_unlock_irqrestore(lock, flags) \
293 typecheck(unsigned long, flags); \
294 _raw_spin_unlock_irqrestore(lock, flags); \
296 #define raw_spin_unlock_bh(lock) _raw_spin_unlock_bh(lock)
298 #define raw_spin_trylock_bh(lock) \
299 __cond_lock(lock, _raw_spin_trylock_bh(lock))
301 #define raw_spin_trylock_irq(lock) \
303 local_irq_disable(); \
304 raw_spin_trylock(lock) ? \
305 1 : ({ local_irq_enable(); 0; }); \
308 #define raw_spin_trylock_irqsave(lock, flags) \
310 local_irq_save(flags); \
311 raw_spin_trylock(lock) ? \
312 1 : ({ local_irq_restore(flags); 0; }); \
315 #ifndef CONFIG_PREEMPT_RT
316 /* Include rwlock functions for !RT */
317 #include <linux/rwlock.h>
321 * Pull the _spin_*()/_read_*()/_write_*() functions/declarations:
323 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
324 # include <linux/spinlock_api_smp.h>
326 # include <linux/spinlock_api_up.h>
329 /* Non PREEMPT_RT kernel, map to raw spinlocks: */
330 #ifndef CONFIG_PREEMPT_RT
333 * Map the spin_lock functions to the raw variants for PREEMPT_RT=n
336 static __always_inline raw_spinlock_t
*spinlock_check(spinlock_t
*lock
)
341 #ifdef CONFIG_DEBUG_SPINLOCK
343 # define spin_lock_init(lock) \
345 static struct lock_class_key __key; \
347 __raw_spin_lock_init(spinlock_check(lock), \
348 #lock, &__key, LD_WAIT_CONFIG); \
353 # define spin_lock_init(_lock) \
355 spinlock_check(_lock); \
356 *(_lock) = __SPIN_LOCK_UNLOCKED(_lock); \
361 static __always_inline
void spin_lock(spinlock_t
*lock
)
363 raw_spin_lock(&lock
->rlock
);
366 static __always_inline
void spin_lock_bh(spinlock_t
*lock
)
368 raw_spin_lock_bh(&lock
->rlock
);
371 static __always_inline
int spin_trylock(spinlock_t
*lock
)
373 return raw_spin_trylock(&lock
->rlock
);
376 #define spin_lock_nested(lock, subclass) \
378 raw_spin_lock_nested(spinlock_check(lock), subclass); \
381 #define spin_lock_nest_lock(lock, nest_lock) \
383 raw_spin_lock_nest_lock(spinlock_check(lock), nest_lock); \
386 static __always_inline
void spin_lock_irq(spinlock_t
*lock
)
388 raw_spin_lock_irq(&lock
->rlock
);
391 #define spin_lock_irqsave(lock, flags) \
393 raw_spin_lock_irqsave(spinlock_check(lock), flags); \
396 #define spin_lock_irqsave_nested(lock, flags, subclass) \
398 raw_spin_lock_irqsave_nested(spinlock_check(lock), flags, subclass); \
401 static __always_inline
void spin_unlock(spinlock_t
*lock
)
403 raw_spin_unlock(&lock
->rlock
);
406 static __always_inline
void spin_unlock_bh(spinlock_t
*lock
)
408 raw_spin_unlock_bh(&lock
->rlock
);
411 static __always_inline
void spin_unlock_irq(spinlock_t
*lock
)
413 raw_spin_unlock_irq(&lock
->rlock
);
416 static __always_inline
void spin_unlock_irqrestore(spinlock_t
*lock
, unsigned long flags
)
418 raw_spin_unlock_irqrestore(&lock
->rlock
, flags
);
421 static __always_inline
int spin_trylock_bh(spinlock_t
*lock
)
423 return raw_spin_trylock_bh(&lock
->rlock
);
426 static __always_inline
int spin_trylock_irq(spinlock_t
*lock
)
428 return raw_spin_trylock_irq(&lock
->rlock
);
431 #define spin_trylock_irqsave(lock, flags) \
433 raw_spin_trylock_irqsave(spinlock_check(lock), flags); \
437 * spin_is_locked() - Check whether a spinlock is locked.
438 * @lock: Pointer to the spinlock.
440 * This function is NOT required to provide any memory ordering
441 * guarantees; it could be used for debugging purposes or, when
442 * additional synchronization is needed, accompanied with other
443 * constructs (memory barriers) enforcing the synchronization.
445 * Returns: 1 if @lock is locked, 0 otherwise.
447 * Note that the function only tells you that the spinlock is
448 * seen to be locked, not that it is locked on your CPU.
450 * Further, on CONFIG_SMP=n builds with CONFIG_DEBUG_SPINLOCK=n,
451 * the return value is always 0 (see include/linux/spinlock_up.h).
452 * Therefore you should not rely heavily on the return value.
454 static __always_inline
int spin_is_locked(spinlock_t
*lock
)
456 return raw_spin_is_locked(&lock
->rlock
);
459 static __always_inline
int spin_is_contended(spinlock_t
*lock
)
461 return raw_spin_is_contended(&lock
->rlock
);
464 #define assert_spin_locked(lock) assert_raw_spin_locked(&(lock)->rlock)
466 #else /* !CONFIG_PREEMPT_RT */
467 # include <linux/spinlock_rt.h>
468 #endif /* CONFIG_PREEMPT_RT */
471 * Pull the atomic_t declaration:
472 * (asm-mips/atomic.h needs above definitions)
474 #include <linux/atomic.h>
476 * atomic_dec_and_lock - lock on reaching reference count zero
477 * @atomic: the atomic counter
478 * @lock: the spinlock in question
480 * Decrements @atomic by 1. If the result is 0, returns true and locks
481 * @lock. Returns false for all other cases.
483 extern int _atomic_dec_and_lock(atomic_t
*atomic
, spinlock_t
*lock
);
484 #define atomic_dec_and_lock(atomic, lock) \
485 __cond_lock(lock, _atomic_dec_and_lock(atomic, lock))
487 extern int _atomic_dec_and_lock_irqsave(atomic_t
*atomic
, spinlock_t
*lock
,
488 unsigned long *flags
);
489 #define atomic_dec_and_lock_irqsave(atomic, lock, flags) \
490 __cond_lock(lock, _atomic_dec_and_lock_irqsave(atomic, lock, &(flags)))
492 int __alloc_bucket_spinlocks(spinlock_t
**locks
, unsigned int *lock_mask
,
493 size_t max_size
, unsigned int cpu_mult
,
494 gfp_t gfp
, const char *name
,
495 struct lock_class_key
*key
);
497 #define alloc_bucket_spinlocks(locks, lock_mask, max_size, cpu_mult, gfp) \
499 static struct lock_class_key key; \
502 ret = __alloc_bucket_spinlocks(locks, lock_mask, max_size, \
503 cpu_mult, gfp, #locks, &key); \
507 void free_bucket_spinlocks(spinlock_t
*locks
);
509 #endif /* __LINUX_SPINLOCK_H */