58cb1bc0e183af3460b3e8b293827371b8d04b64
[android-sdk/platform-bionic.git] / libc / include / stdatomic.h
1 /*-
2  * Copyright (c) 2011 Ed Schouten <ed@FreeBSD.org>
3  *                    David Chisnall <theraven@FreeBSD.org>
4  * All rights reserved.
5  *
6  * Redistribution and use in source and binary forms, with or without
7  * modification, are permitted provided that the following conditions
8  * are met:
9  * 1. Redistributions of source code must retain the above copyright
10  *    notice, this list of conditions and the following disclaimer.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  *    notice, this list of conditions and the following disclaimer in the
13  *    documentation and/or other materials provided with the distribution.
14  *
15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25  * SUCH DAMAGE.
26  *
27  * $FreeBSD$
28  */
30 #ifndef _STDATOMIC_H_
31 #define _STDATOMIC_H_
33 #include <sys/cdefs.h>
36 #if defined(__cplusplus) && __cplusplus >= 201103L && defined(_USING_LIBCXX)
37 # ifdef __clang__
38 #  if __has_feature(cxx_atomic)
39 #   define _STDATOMIC_HAVE_ATOMIC
40 #  endif
41 # else /* gcc */
42 #  if __GNUC_PREREQ(4, 7)
43 #   define _STDATOMIC_HAVE_ATOMIC
44 #  endif
45 # endif
46 #endif
48 #ifdef _STDATOMIC_HAVE_ATOMIC
50 /* We have a usable C++ <atomic>; use it instead.  */
52 #include <atomic>
54 #undef _Atomic
55         /* Also defined by <atomic> for gcc.  But not used in macros. */
56         /* Also a clang intrinsic.                                    */
57         /* Should not be used by client code before this file is      */
58         /* included.  The definitions in <atomic> themselves see      */
59         /* the old definition, as they should.                        */
60         /* Client code sees the following definition.                 */
62 #define _Atomic(t) std::atomic<t>
64 using std::atomic_is_lock_free;
65 using std::atomic_init;
66 using std::atomic_store;
67 using std::atomic_store_explicit;
68 using std::atomic_load;
69 using std::atomic_load_explicit;
70 using std::atomic_exchange;
71 using std::atomic_exchange_explicit;
72 using std::atomic_compare_exchange_strong;
73 using std::atomic_compare_exchange_strong_explicit;
74 using std::atomic_compare_exchange_weak;
75 using std::atomic_compare_exchange_weak_explicit;
76 using std::atomic_fetch_add;
77 using std::atomic_fetch_add_explicit;
78 using std::atomic_fetch_sub;
79 using std::atomic_fetch_sub_explicit;
80 using std::atomic_fetch_or;
81 using std::atomic_fetch_or_explicit;
82 using std::atomic_fetch_xor;
83 using std::atomic_fetch_xor_explicit;
84 using std::atomic_fetch_and;
85 using std::atomic_fetch_and_explicit;
86 using std::atomic_thread_fence;
87 using std::atomic_signal_fence;
89 using std::memory_order;
90 using std::memory_order_relaxed;
91 using std::memory_order_consume;
92 using std::memory_order_acquire;
93 using std::memory_order_release;
94 using std::memory_order_acq_rel;
95 using std::memory_order_seq_cst;
97 using std::atomic_bool;
98 using std::atomic_char;
99 using std::atomic_schar;
100 using std::atomic_uchar;
101 using std::atomic_short;
102 using std::atomic_ushort;
103 using std::atomic_int;
104 using std::atomic_uint;
105 using std::atomic_long;
106 using std::atomic_ulong;
107 using std::atomic_llong;
108 using std::atomic_ullong;
109 using std::atomic_char16_t;
110 using std::atomic_char32_t;
111 using std::atomic_wchar_t;
112 using std::atomic_int_least8_t;
113 using std::atomic_uint_least8_t;
114 using std::atomic_int_least16_t;
115 using std::atomic_uint_least16_t;
116 using std::atomic_int_least32_t;
117 using std::atomic_uint_least32_t;
118 using std::atomic_int_least64_t;
119 using std::atomic_uint_least64_t;
120 using std::atomic_int_fast8_t;
121 using std::atomic_uint_fast8_t;
122 using std::atomic_int_fast16_t;
123 using std::atomic_uint_fast16_t;
124 using std::atomic_int_fast32_t;
125 using std::atomic_uint_fast32_t;
126 using std::atomic_int_fast64_t;
127 using std::atomic_uint_fast64_t;
128 using std::atomic_intptr_t;
129 using std::atomic_uintptr_t;
130 using std::atomic_size_t;
131 using std::atomic_ptrdiff_t;
132 using std::atomic_intmax_t;
133 using std::atomic_uintmax_t;
135 #else /* <atomic> unavailable, possibly because this is C, not C++ */
137 #include <sys/types.h>
138 #include <stdbool.h>
140 /*
141  * C: Do it ourselves.
142  * Note that the runtime representation defined here should be compatible
143  * with the C++ one, i.e. an _Atomic(T) needs to contain the same
144  * bits as a T.
145  */
147 #include <stddef.h>  /* For ptrdiff_t.                          */
148 #include <stdint.h>  /* TODO: Should pollute namespace less.    */
149 #if __STDC_VERSION__ >= 201112L
150 # include <uchar.h>  /* For char16_t and char32_t.              */
151 #endif
153 #ifdef __clang__
154 # if __has_extension(c_atomic) || __has_extension(cxx_atomic)
155 #  define       __CLANG_ATOMICS
156 # else
157 #  error "stdatomic.h does not support your compiler"
158 # endif
159 # if __has_builtin(__sync_swap)
160 #  define __HAS_BUILTIN_SYNC_SWAP
161 # endif
162 #else
163 # if __GNUC_PREREQ(4, 7)
164 #  define       __GNUC_ATOMICS
165 # else
166 #  define       __SYNC_ATOMICS
167 #  ifdef __cplusplus
168 #   define       __ATOMICS_AVOID_DOT_INIT
169 #  endif
170 # endif
171 #endif
173 /*
174  * 7.17.1 Atomic lock-free macros.
175  */
177 #ifdef __GCC_ATOMIC_BOOL_LOCK_FREE
178 #define ATOMIC_BOOL_LOCK_FREE           __GCC_ATOMIC_BOOL_LOCK_FREE
179 #elif defined(__SYNC_ATOMICS)
180 #define ATOMIC_BOOL_LOCK_FREE           2 /* For all modern platforms */
181 #endif
182 #ifdef __GCC_ATOMIC_CHAR_LOCK_FREE
183 #define ATOMIC_CHAR_LOCK_FREE           __GCC_ATOMIC_CHAR_LOCK_FREE
184 #elif defined(__SYNC_ATOMICS)
185 #define ATOMIC_CHAR_LOCK_FREE           2
186 #endif
187 #ifdef __GCC_ATOMIC_CHAR16_T_LOCK_FREE
188 #define ATOMIC_CHAR16_T_LOCK_FREE       __GCC_ATOMIC_CHAR16_T_LOCK_FREE
189 #elif defined(__SYNC_ATOMICS)
190 #define ATOMIC_CHAR16_T_LOCK_FREE       2
191 #endif
192 #ifdef __GCC_ATOMIC_CHAR32_T_LOCK_FREE
193 #define ATOMIC_CHAR32_T_LOCK_FREE       __GCC_ATOMIC_CHAR32_T_LOCK_FREE
194 #elif defined(__SYNC_ATOMICS)
195 #define ATOMIC_CHAR32_T_LOCK_FREE       2
196 #endif
197 #ifdef __GCC_ATOMIC_WCHAR_T_LOCK_FREE
198 #define ATOMIC_WCHAR_T_LOCK_FREE        __GCC_ATOMIC_WCHAR_T_LOCK_FREE
199 #elif defined(__SYNC_ATOMICS)
200 #define ATOMIC_WCHAR_T_LOCK_FREE        2
201 #endif
202 #ifdef __GCC_ATOMIC_SHORT_LOCK_FREE
203 #define ATOMIC_SHORT_LOCK_FREE          __GCC_ATOMIC_SHORT_LOCK_FREE
204 #elif defined(__SYNC_ATOMICS)
205 #define ATOMIC_SHORT_LOCK_FREE          2
206 #endif
207 #ifdef __GCC_ATOMIC_INT_LOCK_FREE
208 #define ATOMIC_INT_LOCK_FREE            __GCC_ATOMIC_INT_LOCK_FREE
209 #elif defined(__SYNC_ATOMICS)
210 #define ATOMIC_INT_LOCK_FREE            2
211 #endif
212 #ifdef __GCC_ATOMIC_LONG_LOCK_FREE
213 #define ATOMIC_LONG_LOCK_FREE           __GCC_ATOMIC_LONG_LOCK_FREE
214 #elif defined(__SYNC_ATOMICS)
215 #define ATOMIC_LONG_LOCK_FREE           2
216 #endif
217 #ifdef __GCC_ATOMIC_LLONG_LOCK_FREE
218 #define ATOMIC_LLONG_LOCK_FREE          __GCC_ATOMIC_LLONG_LOCK_FREE
219 #elif defined(__SYNC_ATOMICS)
220 #define ATOMIC_LLONG_LOCK_FREE          1 /* maybe */
221 #endif
222 #ifdef __GCC_ATOMIC_POINTER_LOCK_FREE
223 #define ATOMIC_POINTER_LOCK_FREE        __GCC_ATOMIC_POINTER_LOCK_FREE
224 #elif defined(__SYNC_ATOMICS)
225 #define ATOMIC_POINTER_LOCK_FREE        2
226 #endif
228 /*
229  * 7.17.2 Initialization.
230  */
232 #if defined(__CLANG_ATOMICS)
233 #define ATOMIC_VAR_INIT(value)          (value)
234 #define atomic_init(obj, value)         __c11_atomic_init(obj, value)
235 #else
236 #ifdef __ATOMICS_AVOID_DOT_INIT
237 #define ATOMIC_VAR_INIT(value)          { value }
238 #else
239 #define ATOMIC_VAR_INIT(value)          { .__val = (value) }
240 #endif
241 #define atomic_init(obj, value)         ((void)((obj)->__val = (value)))
242 #endif
244 /*
245  * Clang and recent GCC both provide predefined macros for the memory
246  * orderings.  If we are using a compiler that doesn't define them, use the
247  * clang values - these will be ignored in the fallback path.
248  */
250 #ifndef __ATOMIC_RELAXED
251 #define __ATOMIC_RELAXED                0
252 #endif
253 #ifndef __ATOMIC_CONSUME
254 #define __ATOMIC_CONSUME                1
255 #endif
256 #ifndef __ATOMIC_ACQUIRE
257 #define __ATOMIC_ACQUIRE                2
258 #endif
259 #ifndef __ATOMIC_RELEASE
260 #define __ATOMIC_RELEASE                3
261 #endif
262 #ifndef __ATOMIC_ACQ_REL
263 #define __ATOMIC_ACQ_REL                4
264 #endif
265 #ifndef __ATOMIC_SEQ_CST
266 #define __ATOMIC_SEQ_CST                5
267 #endif
269 /*
270  * 7.17.3 Order and consistency.
271  *
272  * The memory_order_* constants that denote the barrier behaviour of the
273  * atomic operations.
274  * The enum values must be identical to those used by the
275  * C++ <atomic> header.
276  */
278 typedef enum {
279         memory_order_relaxed = __ATOMIC_RELAXED,
280         memory_order_consume = __ATOMIC_CONSUME,
281         memory_order_acquire = __ATOMIC_ACQUIRE,
282         memory_order_release = __ATOMIC_RELEASE,
283         memory_order_acq_rel = __ATOMIC_ACQ_REL,
284         memory_order_seq_cst = __ATOMIC_SEQ_CST
285 } memory_order;
287 /*
288  * 7.17.4 Fences.
289  */
291 static __inline void
292 atomic_thread_fence(memory_order __order __attribute__((unused)))
295 #ifdef __CLANG_ATOMICS
296         __c11_atomic_thread_fence(__order);
297 #elif defined(__GNUC_ATOMICS)
298         __atomic_thread_fence(__order);
299 #else
300         __sync_synchronize();
301 #endif
304 static __inline void
305 atomic_signal_fence(memory_order __order __attribute__((unused)))
308 #ifdef __CLANG_ATOMICS
309         __c11_atomic_signal_fence(__order);
310 #elif defined(__GNUC_ATOMICS)
311         __atomic_signal_fence(__order);
312 #else
313         __asm volatile ("" ::: "memory");
314 #endif
317 /*
318  * 7.17.5 Lock-free property.
319  */
321 #if defined(_KERNEL)
322 /* Atomics in kernelspace are always lock-free. */
323 #define atomic_is_lock_free(obj) \
324         ((void)(obj), (_Bool)1)
325 #elif defined(__CLANG_ATOMICS)
326 #define atomic_is_lock_free(obj) \
327         __c11_atomic_is_lock_free(sizeof(*(obj)))
328 #elif defined(__GNUC_ATOMICS)
329 #define atomic_is_lock_free(obj) \
330         __atomic_is_lock_free(sizeof((obj)->__val), &(obj)->__val)
331 #else
332 #define atomic_is_lock_free(obj) \
333         ((void)(obj), sizeof((obj)->__val) <= sizeof(void *))
334 #endif
336 /*
337  * 7.17.6 Atomic integer types.
338  */
340 #ifndef __CLANG_ATOMICS
341 /*
342  * No native support for _Atomic(). Place object in structure to prevent
343  * most forms of direct non-atomic access.
344  */
345 #define _Atomic(T)              struct { T volatile __val; }
346 #endif
348 typedef _Atomic(bool)                   atomic_bool;
349 typedef _Atomic(char)                   atomic_char;
350 typedef _Atomic(signed char)            atomic_schar;
351 typedef _Atomic(unsigned char)          atomic_uchar;
352 typedef _Atomic(short)                  atomic_short;
353 typedef _Atomic(unsigned short)         atomic_ushort;
354 typedef _Atomic(int)                    atomic_int;
355 typedef _Atomic(unsigned int)           atomic_uint;
356 typedef _Atomic(long)                   atomic_long;
357 typedef _Atomic(unsigned long)          atomic_ulong;
358 typedef _Atomic(long long)              atomic_llong;
359 typedef _Atomic(unsigned long long)     atomic_ullong;
360 #if __STDC_VERSION__ >= 201112L || __cplusplus >= 201103L
361   typedef _Atomic(char16_t)             atomic_char16_t;
362   typedef _Atomic(char32_t)             atomic_char32_t;
363 #endif
364 typedef _Atomic(wchar_t)                atomic_wchar_t;
365 typedef _Atomic(int_least8_t)           atomic_int_least8_t;
366 typedef _Atomic(uint_least8_t)  atomic_uint_least8_t;
367 typedef _Atomic(int_least16_t)  atomic_int_least16_t;
368 typedef _Atomic(uint_least16_t) atomic_uint_least16_t;
369 typedef _Atomic(int_least32_t)  atomic_int_least32_t;
370 typedef _Atomic(uint_least32_t) atomic_uint_least32_t;
371 typedef _Atomic(int_least64_t)  atomic_int_least64_t;
372 typedef _Atomic(uint_least64_t) atomic_uint_least64_t;
373 typedef _Atomic(int_fast8_t)            atomic_int_fast8_t;
374 typedef _Atomic(uint_fast8_t)           atomic_uint_fast8_t;
375 typedef _Atomic(int_fast16_t)           atomic_int_fast16_t;
376 typedef _Atomic(uint_fast16_t)  atomic_uint_fast16_t;
377 typedef _Atomic(int_fast32_t)           atomic_int_fast32_t;
378 typedef _Atomic(uint_fast32_t)  atomic_uint_fast32_t;
379 typedef _Atomic(int_fast64_t)           atomic_int_fast64_t;
380 typedef _Atomic(uint_fast64_t)  atomic_uint_fast64_t;
381 typedef _Atomic(intptr_t)               atomic_intptr_t;
382 typedef _Atomic(uintptr_t)              atomic_uintptr_t;
383 typedef _Atomic(size_t)         atomic_size_t;
384 typedef _Atomic(ptrdiff_t)              atomic_ptrdiff_t;
385 typedef _Atomic(intmax_t)               atomic_intmax_t;
386 typedef _Atomic(uintmax_t)              atomic_uintmax_t;
388 /*
389  * 7.17.7 Operations on atomic types.
390  */
392 /*
393  * Compiler-specific operations.
394  */
396 #if defined(__CLANG_ATOMICS)
397 #define atomic_compare_exchange_strong_explicit(object, expected,       \
398     desired, success, failure)                                          \
399         __c11_atomic_compare_exchange_strong(object, expected, desired, \
400             success, failure)
401 #define atomic_compare_exchange_weak_explicit(object, expected,         \
402     desired, success, failure)                                          \
403         __c11_atomic_compare_exchange_weak(object, expected, desired,   \
404             success, failure)
405 #define atomic_exchange_explicit(object, desired, order)                \
406         __c11_atomic_exchange(object, desired, order)
407 #define atomic_fetch_add_explicit(object, operand, order)               \
408         __c11_atomic_fetch_add(object, operand, order)
409 #define atomic_fetch_and_explicit(object, operand, order)               \
410         __c11_atomic_fetch_and(object, operand, order)
411 #define atomic_fetch_or_explicit(object, operand, order)                \
412         __c11_atomic_fetch_or(object, operand, order)
413 #define atomic_fetch_sub_explicit(object, operand, order)               \
414         __c11_atomic_fetch_sub(object, operand, order)
415 #define atomic_fetch_xor_explicit(object, operand, order)               \
416         __c11_atomic_fetch_xor(object, operand, order)
417 #define atomic_load_explicit(object, order)                             \
418         __c11_atomic_load(object, order)
419 #define atomic_store_explicit(object, desired, order)                   \
420         __c11_atomic_store(object, desired, order)
421 #elif defined(__GNUC_ATOMICS)
422 #define atomic_compare_exchange_strong_explicit(object, expected,       \
423     desired, success, failure)                                          \
424         __atomic_compare_exchange_n(&(object)->__val, expected,         \
425             desired, 0, success, failure)
426 #define atomic_compare_exchange_weak_explicit(object, expected,         \
427     desired, success, failure)                                          \
428         __atomic_compare_exchange_n(&(object)->__val, expected,         \
429             desired, 1, success, failure)
430 #define atomic_exchange_explicit(object, desired, order)                \
431         __atomic_exchange_n(&(object)->__val, desired, order)
432 #define atomic_fetch_add_explicit(object, operand, order)               \
433         __atomic_fetch_add(&(object)->__val, operand, order)
434 #define atomic_fetch_and_explicit(object, operand, order)               \
435         __atomic_fetch_and(&(object)->__val, operand, order)
436 #define atomic_fetch_or_explicit(object, operand, order)                \
437         __atomic_fetch_or(&(object)->__val, operand, order)
438 #define atomic_fetch_sub_explicit(object, operand, order)               \
439         __atomic_fetch_sub(&(object)->__val, operand, order)
440 #define atomic_fetch_xor_explicit(object, operand, order)               \
441         __atomic_fetch_xor(&(object)->__val, operand, order)
442 #define atomic_load_explicit(object, order)                             \
443         __atomic_load_n(&(object)->__val, order)
444 #define atomic_store_explicit(object, desired, order)                   \
445         __atomic_store_n(&(object)->__val, desired, order)
446 #else
447 #define __atomic_apply_stride(object, operand) \
448         (((__typeof__((object)->__val))0) + (operand))
449 #define atomic_compare_exchange_strong_explicit(object, expected,       \
450     desired, success, failure)  __extension__ ({                        \
451         __typeof__(expected) __ep = (expected);                         \
452         __typeof__(*__ep) __e = *__ep;                                  \
453         (void)(success); (void)(failure);                               \
454         (bool)((*__ep = __sync_val_compare_and_swap(&(object)->__val,   \
455             __e, desired)) == __e);                                     \
456 })
457 #define atomic_compare_exchange_weak_explicit(object, expected,         \
458     desired, success, failure)                                          \
459         atomic_compare_exchange_strong_explicit(object, expected,       \
460                 desired, success, failure)
461 #ifdef __HAS_BUILTIN_SYNC_SWAP
462 /* Clang provides a full-barrier atomic exchange - use it if available. */
463 #define atomic_exchange_explicit(object, desired, order)                \
464         ((void)(order), __sync_swap(&(object)->__val, desired))
465 #else
466 /*
467  * __sync_lock_test_and_set() is only an acquire barrier in theory (although in
468  * practice it is usually a full barrier) so we need an explicit barrier before
469  * it.
470  */
471 #define atomic_exchange_explicit(object, desired, order)                \
472 __extension__ ({                                                        \
473         __typeof__(object) __o = (object);                              \
474         __typeof__(desired) __d = (desired);                            \
475         (void)(order);                                                  \
476         __sync_synchronize();                                           \
477         __sync_lock_test_and_set(&(__o)->__val, __d);                   \
478 })
479 #endif
480 #define atomic_fetch_add_explicit(object, operand, order)               \
481         ((void)(order), __sync_fetch_and_add(&(object)->__val,          \
482             __atomic_apply_stride(object, operand)))
483 #define atomic_fetch_and_explicit(object, operand, order)               \
484         ((void)(order), __sync_fetch_and_and(&(object)->__val, operand))
485 #define atomic_fetch_or_explicit(object, operand, order)                \
486         ((void)(order), __sync_fetch_and_or(&(object)->__val, operand))
487 #define atomic_fetch_sub_explicit(object, operand, order)               \
488         ((void)(order), __sync_fetch_and_sub(&(object)->__val,          \
489             __atomic_apply_stride(object, operand)))
490 #define atomic_fetch_xor_explicit(object, operand, order)               \
491         ((void)(order), __sync_fetch_and_xor(&(object)->__val, operand))
492 #define atomic_load_explicit(object, order)                             \
493         ((void)(order), __sync_fetch_and_add(&(object)->__val, 0))
494 #define atomic_store_explicit(object, desired, order)                   \
495         ((void)atomic_exchange_explicit(object, desired, order))
496 #endif
498 /*
499  * Convenience functions.
500  *
501  * Don't provide these in kernel space. In kernel space, we should be
502  * disciplined enough to always provide explicit barriers.
503  */
505 #ifndef _KERNEL
506 #define atomic_compare_exchange_strong(object, expected, desired)       \
507         atomic_compare_exchange_strong_explicit(object, expected,       \
508             desired, memory_order_seq_cst, memory_order_seq_cst)
509 #define atomic_compare_exchange_weak(object, expected, desired)         \
510         atomic_compare_exchange_weak_explicit(object, expected,         \
511             desired, memory_order_seq_cst, memory_order_seq_cst)
512 #define atomic_exchange(object, desired)                                \
513         atomic_exchange_explicit(object, desired, memory_order_seq_cst)
514 #define atomic_fetch_add(object, operand)                               \
515         atomic_fetch_add_explicit(object, operand, memory_order_seq_cst)
516 #define atomic_fetch_and(object, operand)                               \
517         atomic_fetch_and_explicit(object, operand, memory_order_seq_cst)
518 #define atomic_fetch_or(object, operand)                                \
519         atomic_fetch_or_explicit(object, operand, memory_order_seq_cst)
520 #define atomic_fetch_sub(object, operand)                               \
521         atomic_fetch_sub_explicit(object, operand, memory_order_seq_cst)
522 #define atomic_fetch_xor(object, operand)                               \
523         atomic_fetch_xor_explicit(object, operand, memory_order_seq_cst)
524 #define atomic_load(object)                                             \
525         atomic_load_explicit(object, memory_order_seq_cst)
526 #define atomic_store(object, desired)                                   \
527         atomic_store_explicit(object, desired, memory_order_seq_cst)
528 #endif /* !_KERNEL */
530 /*
531  * 7.17.8 Atomic flag type and operations.
532  *
533  * XXX: Assume atomic_bool can be used as an atomic_flag. Is there some
534  * kind of compiler built-in type we could use?
535  */
537 typedef struct {
538         atomic_bool     __flag;
539 } atomic_flag;
541 #define ATOMIC_FLAG_INIT                { ATOMIC_VAR_INIT(false) }
543 static __inline bool
544 atomic_flag_test_and_set_explicit(volatile atomic_flag *__object,
545     memory_order __order)
547         return (atomic_exchange_explicit(&__object->__flag, 1, __order));
550 static __inline void
551 atomic_flag_clear_explicit(volatile atomic_flag *__object, memory_order __order)
554         atomic_store_explicit(&__object->__flag, 0, __order);
557 #ifndef _KERNEL
558 static __inline bool
559 atomic_flag_test_and_set(volatile atomic_flag *__object)
562         return (atomic_flag_test_and_set_explicit(__object,
563             memory_order_seq_cst));
566 static __inline void
567 atomic_flag_clear(volatile atomic_flag *__object)
570         atomic_flag_clear_explicit(__object, memory_order_seq_cst);
572 #endif /* !_KERNEL */
574 #endif /* <atomic> unavailable */
576 #endif /* !_STDATOMIC_H_ */