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TOMOYO Linux Cross Reference
Linux/include/linux/spinlock.h

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  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.h:
 16  *                        defines the generic type and initializers
 17  *
 18  *  asm/spinlock.h:       contains the arch_spin_*()/etc. lowlevel
 19  *                        implementations, mostly inline assembly code
 20  *
 21  *   (also included on UP-debug builds:)
 22  *
 23  *  linux/spinlock_api_smp.h:
 24  *                        contains the prototypes for the _spin_*() APIs.
 25  *
 26  *  linux/spinlock.h:     builds the final spin_*() APIs.
 27  *
 28  * on UP builds:
 29  *
 30  *  linux/spinlock_type_up.h:
 31  *                        contains the generic, simplified UP spinlock type.
 32  *                        (which is an empty structure on non-debug builds)
 33  *
 34  *  linux/spinlock_types.h:
 35  *                        defines the generic type and initializers
 36  *
 37  *  linux/spinlock_up.h:
 38  *                        contains the arch_spin_*()/etc. version of UP
 39  *                        builds. (which are NOPs on non-debug, non-preempt
 40  *                        builds)
 41  *
 42  *   (included on UP-non-debug builds:)
 43  *
 44  *  linux/spinlock_api_up.h:
 45  *                        builds the _spin_*() APIs.
 46  *
 47  *  linux/spinlock.h:     builds the final spin_*() APIs.
 48  */
 49 
 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>
 61 
 62 
 63 /*
 64  * Must define these before including other files, inline functions need them
 65  */
 66 #define LOCK_SECTION_NAME ".text..lock."KBUILD_BASENAME
 67 
 68 #define LOCK_SECTION_START(extra)               \
 69         ".subsection 1\n\t"                     \
 70         extra                                   \
 71         ".ifndef " LOCK_SECTION_NAME "\n\t"     \
 72         LOCK_SECTION_NAME ":\n\t"               \
 73         ".endif\n"
 74 
 75 #define LOCK_SECTION_END                        \
 76         ".previous\n\t"
 77 
 78 #define __lockfunc __attribute__((section(".spinlock.text")))
 79 
 80 /*
 81  * Pull the arch_spinlock_t and arch_rwlock_t definitions:
 82  */
 83 #include <linux/spinlock_types.h>
 84 
 85 /*
 86  * Pull the arch_spin*() functions/declarations (UP-nondebug doesn't need them):
 87  */
 88 #ifdef CONFIG_SMP
 89 # include <asm/spinlock.h>
 90 #else
 91 # include <linux/spinlock_up.h>
 92 #endif
 93 
 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);
 97 # define raw_spin_lock_init(lock)                               \
 98 do {                                                            \
 99         static struct lock_class_key __key;                     \
100                                                                 \
101         __raw_spin_lock_init((lock), #lock, &__key);            \
102 } while (0)
103 
104 #else
105 # define raw_spin_lock_init(lock)                               \
106         do { *(lock) = __RAW_SPIN_LOCK_UNLOCKED(lock); } while (0)
107 #endif
108 
109 #define raw_spin_is_locked(lock)        arch_spin_is_locked(&(lock)->raw_lock)
110 
111 #ifdef arch_spin_is_contended
112 #define raw_spin_is_contended(lock)     arch_spin_is_contended(&(lock)->raw_lock)
113 #else
114 #define raw_spin_is_contended(lock)     (((void)(lock), 0))
115 #endif /*arch_spin_is_contended*/
116 
117 /*
118  * smp_mb__after_spinlock() provides the equivalent of a full memory barrier
119  * between program-order earlier lock acquisitions and program-order later
120  * memory accesses.
121  *
122  * This guarantees that the following two properties hold:
123  *
124  *   1) Given the snippet:
125  *
126  *        { X = 0;  Y = 0; }
127  *
128  *        CPU0                          CPU1
129  *
130  *        WRITE_ONCE(X, 1);             WRITE_ONCE(Y, 1);
131  *        spin_lock(S);                 smp_mb();
132  *        smp_mb__after_spinlock();     r1 = READ_ONCE(X);
133  *        r0 = READ_ONCE(Y);
134  *        spin_unlock(S);
135  *
136  *      it is forbidden that CPU0 does not observe CPU1's store to Y (r0 = 0)
137  *      and CPU1 does not observe CPU0's store to X (r1 = 0); see the comments
138  *      preceding the call to smp_mb__after_spinlock() in __schedule() and in
139  *      try_to_wake_up().
140  *
141  *   2) Given the snippet:
142  *
143  *  { X = 0;  Y = 0; }
144  *
145  *  CPU0                CPU1                            CPU2
146  *
147  *  spin_lock(S);       spin_lock(S);                   r1 = READ_ONCE(Y);
148  *  WRITE_ONCE(X, 1);   smp_mb__after_spinlock();       smp_rmb();
149  *  spin_unlock(S);     r0 = READ_ONCE(X);              r2 = READ_ONCE(X);
150  *                      WRITE_ONCE(Y, 1);
151  *                      spin_unlock(S);
152  *
153  *      it is forbidden that CPU0's critical section executes before CPU1's
154  *      critical section (r0 = 1), CPU2 observes CPU1's store to Y (r1 = 1)
155  *      and CPU2 does not observe CPU0's store to X (r2 = 0); see the comments
156  *      preceding the calls to smp_rmb() in try_to_wake_up() for similar
157  *      snippets but "projected" onto two CPUs.
158  *
159  * Property (2) upgrades the lock to an RCsc lock.
160  *
161  * Since most load-store architectures implement ACQUIRE with an smp_mb() after
162  * the LL/SC loop, they need no further barriers. Similarly all our TSO
163  * architectures imply an smp_mb() for each atomic instruction and equally don't
164  * need more.
165  *
166  * Architectures that can implement ACQUIRE better need to take care.
167  */
168 #ifndef smp_mb__after_spinlock
169 #define smp_mb__after_spinlock()        do { } while (0)
170 #endif
171 
172 #ifdef CONFIG_DEBUG_SPINLOCK
173  extern void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock);
174 #define do_raw_spin_lock_flags(lock, flags) do_raw_spin_lock(lock)
175  extern int do_raw_spin_trylock(raw_spinlock_t *lock);
176  extern void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock);
177 #else
178 static inline void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock)
179 {
180         __acquire(lock);
181         arch_spin_lock(&lock->raw_lock);
182         mmiowb_spin_lock();
183 }
184 
185 #ifndef arch_spin_lock_flags
186 #define arch_spin_lock_flags(lock, flags)       arch_spin_lock(lock)
187 #endif
188 
189 static inline void
190 do_raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long *flags) __acquires(lock)
191 {
192         __acquire(lock);
193         arch_spin_lock_flags(&lock->raw_lock, *flags);
194         mmiowb_spin_lock();
195 }
196 
197 static inline int do_raw_spin_trylock(raw_spinlock_t *lock)
198 {
199         int ret = arch_spin_trylock(&(lock)->raw_lock);
200 
201         if (ret)
202                 mmiowb_spin_lock();
203 
204         return ret;
205 }
206 
207 static inline void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock)
208 {
209         mmiowb_spin_unlock();
210         arch_spin_unlock(&lock->raw_lock);
211         __release(lock);
212 }
213 #endif
214 
215 /*
216  * Define the various spin_lock methods.  Note we define these
217  * regardless of whether CONFIG_SMP or CONFIG_PREEMPTION are set. The
218  * various methods are defined as nops in the case they are not
219  * required.
220  */
221 #define raw_spin_trylock(lock)  __cond_lock(lock, _raw_spin_trylock(lock))
222 
223 #define raw_spin_lock(lock)     _raw_spin_lock(lock)
224 
225 #ifdef CONFIG_DEBUG_LOCK_ALLOC
226 # define raw_spin_lock_nested(lock, subclass) \
227         _raw_spin_lock_nested(lock, subclass)
228 
229 # define raw_spin_lock_nest_lock(lock, nest_lock)                       \
230          do {                                                           \
231                  typecheck(struct lockdep_map *, &(nest_lock)->dep_map);\
232                  _raw_spin_lock_nest_lock(lock, &(nest_lock)->dep_map); \
233          } while (0)
234 #else
235 /*
236  * Always evaluate the 'subclass' argument to avoid that the compiler
237  * warns about set-but-not-used variables when building with
238  * CONFIG_DEBUG_LOCK_ALLOC=n and with W=1.
239  */
240 # define raw_spin_lock_nested(lock, subclass)           \
241         _raw_spin_lock(((void)(subclass), (lock)))
242 # define raw_spin_lock_nest_lock(lock, nest_lock)       _raw_spin_lock(lock)
243 #endif
244 
245 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
246 
247 #define raw_spin_lock_irqsave(lock, flags)                      \
248         do {                                            \
249                 typecheck(unsigned long, flags);        \
250                 flags = _raw_spin_lock_irqsave(lock);   \
251         } while (0)
252 
253 #ifdef CONFIG_DEBUG_LOCK_ALLOC
254 #define raw_spin_lock_irqsave_nested(lock, flags, subclass)             \
255         do {                                                            \
256                 typecheck(unsigned long, flags);                        \
257                 flags = _raw_spin_lock_irqsave_nested(lock, subclass);  \
258         } while (0)
259 #else
260 #define raw_spin_lock_irqsave_nested(lock, flags, subclass)             \
261         do {                                                            \
262                 typecheck(unsigned long, flags);                        \
263                 flags = _raw_spin_lock_irqsave(lock);                   \
264         } while (0)
265 #endif
266 
267 #else
268 
269 #define raw_spin_lock_irqsave(lock, flags)              \
270         do {                                            \
271                 typecheck(unsigned long, flags);        \
272                 _raw_spin_lock_irqsave(lock, flags);    \
273         } while (0)
274 
275 #define raw_spin_lock_irqsave_nested(lock, flags, subclass)     \
276         raw_spin_lock_irqsave(lock, flags)
277 
278 #endif
279 
280 #define raw_spin_lock_irq(lock)         _raw_spin_lock_irq(lock)
281 #define raw_spin_lock_bh(lock)          _raw_spin_lock_bh(lock)
282 #define raw_spin_unlock(lock)           _raw_spin_unlock(lock)
283 #define raw_spin_unlock_irq(lock)       _raw_spin_unlock_irq(lock)
284 
285 #define raw_spin_unlock_irqrestore(lock, flags)         \
286         do {                                                    \
287                 typecheck(unsigned long, flags);                \
288                 _raw_spin_unlock_irqrestore(lock, flags);       \
289         } while (0)
290 #define raw_spin_unlock_bh(lock)        _raw_spin_unlock_bh(lock)
291 
292 #define raw_spin_trylock_bh(lock) \
293         __cond_lock(lock, _raw_spin_trylock_bh(lock))
294 
295 #define raw_spin_trylock_irq(lock) \
296 ({ \
297         local_irq_disable(); \
298         raw_spin_trylock(lock) ? \
299         1 : ({ local_irq_enable(); 0;  }); \
300 })
301 
302 #define raw_spin_trylock_irqsave(lock, flags) \
303 ({ \
304         local_irq_save(flags); \
305         raw_spin_trylock(lock) ? \
306         1 : ({ local_irq_restore(flags); 0; }); \
307 })
308 
309 /* Include rwlock functions */
310 #include <linux/rwlock.h>
311 
312 /*
313  * Pull the _spin_*()/_read_*()/_write_*() functions/declarations:
314  */
315 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
316 # include <linux/spinlock_api_smp.h>
317 #else
318 # include <linux/spinlock_api_up.h>
319 #endif
320 
321 /*
322  * Map the spin_lock functions to the raw variants for PREEMPT_RT=n
323  */
324 
325 static __always_inline raw_spinlock_t *spinlock_check(spinlock_t *lock)
326 {
327         return &lock->rlock;
328 }
329 
330 #define spin_lock_init(_lock)                           \
331 do {                                                    \
332         spinlock_check(_lock);                          \
333         raw_spin_lock_init(&(_lock)->rlock);            \
334 } while (0)
335 
336 static __always_inline void spin_lock(spinlock_t *lock)
337 {
338         raw_spin_lock(&lock->rlock);
339 }
340 
341 static __always_inline void spin_lock_bh(spinlock_t *lock)
342 {
343         raw_spin_lock_bh(&lock->rlock);
344 }
345 
346 static __always_inline int spin_trylock(spinlock_t *lock)
347 {
348         return raw_spin_trylock(&lock->rlock);
349 }
350 
351 #define spin_lock_nested(lock, subclass)                        \
352 do {                                                            \
353         raw_spin_lock_nested(spinlock_check(lock), subclass);   \
354 } while (0)
355 
356 #define spin_lock_nest_lock(lock, nest_lock)                            \
357 do {                                                                    \
358         raw_spin_lock_nest_lock(spinlock_check(lock), nest_lock);       \
359 } while (0)
360 
361 static __always_inline void spin_lock_irq(spinlock_t *lock)
362 {
363         raw_spin_lock_irq(&lock->rlock);
364 }
365 
366 #define spin_lock_irqsave(lock, flags)                          \
367 do {                                                            \
368         raw_spin_lock_irqsave(spinlock_check(lock), flags);     \
369 } while (0)
370 
371 #define spin_lock_irqsave_nested(lock, flags, subclass)                 \
372 do {                                                                    \
373         raw_spin_lock_irqsave_nested(spinlock_check(lock), flags, subclass); \
374 } while (0)
375 
376 static __always_inline void spin_unlock(spinlock_t *lock)
377 {
378         raw_spin_unlock(&lock->rlock);
379 }
380 
381 static __always_inline void spin_unlock_bh(spinlock_t *lock)
382 {
383         raw_spin_unlock_bh(&lock->rlock);
384 }
385 
386 static __always_inline void spin_unlock_irq(spinlock_t *lock)
387 {
388         raw_spin_unlock_irq(&lock->rlock);
389 }
390 
391 static __always_inline void spin_unlock_irqrestore(spinlock_t *lock, unsigned long flags)
392 {
393         raw_spin_unlock_irqrestore(&lock->rlock, flags);
394 }
395 
396 static __always_inline int spin_trylock_bh(spinlock_t *lock)
397 {
398         return raw_spin_trylock_bh(&lock->rlock);
399 }
400 
401 static __always_inline int spin_trylock_irq(spinlock_t *lock)
402 {
403         return raw_spin_trylock_irq(&lock->rlock);
404 }
405 
406 #define spin_trylock_irqsave(lock, flags)                       \
407 ({                                                              \
408         raw_spin_trylock_irqsave(spinlock_check(lock), flags); \
409 })
410 
411 /**
412  * spin_is_locked() - Check whether a spinlock is locked.
413  * @lock: Pointer to the spinlock.
414  *
415  * This function is NOT required to provide any memory ordering
416  * guarantees; it could be used for debugging purposes or, when
417  * additional synchronization is needed, accompanied with other
418  * constructs (memory barriers) enforcing the synchronization.
419  *
420  * Returns: 1 if @lock is locked, 0 otherwise.
421  *
422  * Note that the function only tells you that the spinlock is
423  * seen to be locked, not that it is locked on your CPU.
424  *
425  * Further, on CONFIG_SMP=n builds with CONFIG_DEBUG_SPINLOCK=n,
426  * the return value is always 0 (see include/linux/spinlock_up.h).
427  * Therefore you should not rely heavily on the return value.
428  */
429 static __always_inline int spin_is_locked(spinlock_t *lock)
430 {
431         return raw_spin_is_locked(&lock->rlock);
432 }
433 
434 static __always_inline int spin_is_contended(spinlock_t *lock)
435 {
436         return raw_spin_is_contended(&lock->rlock);
437 }
438 
439 #define assert_spin_locked(lock)        assert_raw_spin_locked(&(lock)->rlock)
440 
441 /*
442  * Pull the atomic_t declaration:
443  * (asm-mips/atomic.h needs above definitions)
444  */
445 #include <linux/atomic.h>
446 /**
447  * atomic_dec_and_lock - lock on reaching reference count zero
448  * @atomic: the atomic counter
449  * @lock: the spinlock in question
450  *
451  * Decrements @atomic by 1.  If the result is 0, returns true and locks
452  * @lock.  Returns false for all other cases.
453  */
454 extern int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock);
455 #define atomic_dec_and_lock(atomic, lock) \
456                 __cond_lock(lock, _atomic_dec_and_lock(atomic, lock))
457 
458 extern int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock,
459                                         unsigned long *flags);
460 #define atomic_dec_and_lock_irqsave(atomic, lock, flags) \
461                 __cond_lock(lock, _atomic_dec_and_lock_irqsave(atomic, lock, &(flags)))
462 
463 int __alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *lock_mask,
464                              size_t max_size, unsigned int cpu_mult,
465                              gfp_t gfp, const char *name,
466                              struct lock_class_key *key);
467 
468 #define alloc_bucket_spinlocks(locks, lock_mask, max_size, cpu_mult, gfp)    \
469         ({                                                                   \
470                 static struct lock_class_key key;                            \
471                 int ret;                                                     \
472                                                                              \
473                 ret = __alloc_bucket_spinlocks(locks, lock_mask, max_size,   \
474                                                cpu_mult, gfp, #locks, &key); \
475                 ret;                                                         \
476         })
477 
478 void free_bucket_spinlocks(spinlock_t *locks);
479 
480 #endif /* __LINUX_SPINLOCK_H */
481 

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