The Design and Implementation of the FreeBSD Operating System, Second Edition
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sys/sys/stdatomic.h

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    1 /*-
    2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
    3  *
    4  * Copyright (c) 2011 Ed Schouten <ed@FreeBSD.org>
    5  *                    David Chisnall <theraven@FreeBSD.org>
    6  * All rights reserved.
    7  *
    8  * Redistribution and use in source and binary forms, with or without
    9  * modification, are permitted provided that the following conditions
   10  * are met:
   11  * 1. Redistributions of source code must retain the above copyright
   12  *    notice, this list of conditions and the following disclaimer.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in the
   15  *    documentation and/or other materials provided with the distribution.
   16  *
   17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   27  * SUCH DAMAGE.
   28  *
   29  * $FreeBSD$
   30  */
   31 
   32 #ifndef _STDATOMIC_H_
   33 #define _STDATOMIC_H_
   34 
   35 #include <sys/cdefs.h>
   36 #include <sys/_types.h>
   37 
   38 #if __has_extension(c_atomic) || __has_extension(cxx_atomic)
   39 #define __CLANG_ATOMICS
   40 #elif __GNUC_PREREQ__(4, 7)
   41 #define __GNUC_ATOMICS
   42 #elif defined(__GNUC__)
   43 #define __SYNC_ATOMICS
   44 #else
   45 #error "stdatomic.h does not support your compiler"
   46 #endif
   47 
   48 /*
   49  * 7.17.1 Atomic lock-free macros.
   50  */
   51 
   52 #ifdef __GCC_ATOMIC_BOOL_LOCK_FREE
   53 #define ATOMIC_BOOL_LOCK_FREE           __GCC_ATOMIC_BOOL_LOCK_FREE
   54 #endif
   55 #ifdef __GCC_ATOMIC_CHAR_LOCK_FREE
   56 #define ATOMIC_CHAR_LOCK_FREE           __GCC_ATOMIC_CHAR_LOCK_FREE
   57 #endif
   58 #ifdef __GCC_ATOMIC_CHAR16_T_LOCK_FREE
   59 #define ATOMIC_CHAR16_T_LOCK_FREE       __GCC_ATOMIC_CHAR16_T_LOCK_FREE
   60 #endif
   61 #ifdef __GCC_ATOMIC_CHAR32_T_LOCK_FREE
   62 #define ATOMIC_CHAR32_T_LOCK_FREE       __GCC_ATOMIC_CHAR32_T_LOCK_FREE
   63 #endif
   64 #ifdef __GCC_ATOMIC_WCHAR_T_LOCK_FREE
   65 #define ATOMIC_WCHAR_T_LOCK_FREE        __GCC_ATOMIC_WCHAR_T_LOCK_FREE
   66 #endif
   67 #ifdef __GCC_ATOMIC_SHORT_LOCK_FREE
   68 #define ATOMIC_SHORT_LOCK_FREE          __GCC_ATOMIC_SHORT_LOCK_FREE
   69 #endif
   70 #ifdef __GCC_ATOMIC_INT_LOCK_FREE
   71 #define ATOMIC_INT_LOCK_FREE            __GCC_ATOMIC_INT_LOCK_FREE
   72 #endif
   73 #ifdef __GCC_ATOMIC_LONG_LOCK_FREE
   74 #define ATOMIC_LONG_LOCK_FREE           __GCC_ATOMIC_LONG_LOCK_FREE
   75 #endif
   76 #ifdef __GCC_ATOMIC_LLONG_LOCK_FREE
   77 #define ATOMIC_LLONG_LOCK_FREE          __GCC_ATOMIC_LLONG_LOCK_FREE
   78 #endif
   79 #ifdef __GCC_ATOMIC_POINTER_LOCK_FREE
   80 #define ATOMIC_POINTER_LOCK_FREE        __GCC_ATOMIC_POINTER_LOCK_FREE
   81 #endif
   82 
   83 /*
   84  * 7.17.2 Initialization.
   85  */
   86 
   87 #if defined(__CLANG_ATOMICS)
   88 #define ATOMIC_VAR_INIT(value)          (value)
   89 #define atomic_init(obj, value)         __c11_atomic_init(obj, value)
   90 #else
   91 #define ATOMIC_VAR_INIT(value)          { .__val = (value) }
   92 #define atomic_init(obj, value)         ((void)((obj)->__val = (value)))
   93 #endif
   94 
   95 /*
   96  * Clang and recent GCC both provide predefined macros for the memory
   97  * orderings.  If we are using a compiler that doesn't define them, use the
   98  * clang values - these will be ignored in the fallback path.
   99  */
  100 
  101 #ifndef __ATOMIC_RELAXED
  102 #define __ATOMIC_RELAXED                0
  103 #endif
  104 #ifndef __ATOMIC_CONSUME
  105 #define __ATOMIC_CONSUME                1
  106 #endif
  107 #ifndef __ATOMIC_ACQUIRE
  108 #define __ATOMIC_ACQUIRE                2
  109 #endif
  110 #ifndef __ATOMIC_RELEASE
  111 #define __ATOMIC_RELEASE                3
  112 #endif
  113 #ifndef __ATOMIC_ACQ_REL
  114 #define __ATOMIC_ACQ_REL                4
  115 #endif
  116 #ifndef __ATOMIC_SEQ_CST
  117 #define __ATOMIC_SEQ_CST                5
  118 #endif
  119 
  120 /*
  121  * 7.17.3 Order and consistency.
  122  *
  123  * The memory_order_* constants that denote the barrier behaviour of the
  124  * atomic operations.
  125  */
  126 
  127 typedef enum {
  128         memory_order_relaxed = __ATOMIC_RELAXED,
  129         memory_order_consume = __ATOMIC_CONSUME,
  130         memory_order_acquire = __ATOMIC_ACQUIRE,
  131         memory_order_release = __ATOMIC_RELEASE,
  132         memory_order_acq_rel = __ATOMIC_ACQ_REL,
  133         memory_order_seq_cst = __ATOMIC_SEQ_CST
  134 } memory_order;
  135 
  136 /*
  137  * 7.17.4 Fences.
  138  */
  139 
  140 static __inline void
  141 atomic_thread_fence(memory_order __order __unused)
  142 {
  143 
  144 #ifdef __CLANG_ATOMICS
  145         __c11_atomic_thread_fence(__order);
  146 #elif defined(__GNUC_ATOMICS)
  147         __atomic_thread_fence(__order);
  148 #else
  149         __sync_synchronize();
  150 #endif
  151 }
  152 
  153 static __inline void
  154 atomic_signal_fence(memory_order __order __unused)
  155 {
  156 
  157 #ifdef __CLANG_ATOMICS
  158         __c11_atomic_signal_fence(__order);
  159 #elif defined(__GNUC_ATOMICS)
  160         __atomic_signal_fence(__order);
  161 #else
  162         __asm volatile ("" ::: "memory");
  163 #endif
  164 }
  165 
  166 #if defined(__cplusplus) && !defined(_Bool)
  167 #define _Bool   bool
  168 #define __bool_locally_defined
  169 #endif
  170 
  171 /*
  172  * 7.17.5 Lock-free property.
  173  */
  174 
  175 #if defined(_KERNEL)
  176 /* Atomics in kernelspace are always lock-free. */
  177 #define atomic_is_lock_free(obj) \
  178         ((void)(obj), (_Bool)1)
  179 #elif defined(__CLANG_ATOMICS) || defined(__GNUC_ATOMICS)
  180 #define atomic_is_lock_free(obj) \
  181         __atomic_is_lock_free(sizeof(*(obj)), obj)
  182 #else
  183 #define atomic_is_lock_free(obj) \
  184         ((void)(obj), sizeof((obj)->__val) <= sizeof(void *))
  185 #endif
  186 
  187 /*
  188  * 7.17.6 Atomic integer types.
  189  */
  190 
  191 typedef _Atomic(_Bool)                  atomic_bool;
  192 typedef _Atomic(char)                   atomic_char;
  193 typedef _Atomic(signed char)            atomic_schar;
  194 typedef _Atomic(unsigned char)          atomic_uchar;
  195 typedef _Atomic(short)                  atomic_short;
  196 typedef _Atomic(unsigned short)         atomic_ushort;
  197 typedef _Atomic(int)                    atomic_int;
  198 typedef _Atomic(unsigned int)           atomic_uint;
  199 typedef _Atomic(long)                   atomic_long;
  200 typedef _Atomic(unsigned long)          atomic_ulong;
  201 typedef _Atomic(long long)              atomic_llong;
  202 typedef _Atomic(unsigned long long)     atomic_ullong;
  203 typedef _Atomic(__char16_t)             atomic_char16_t;
  204 typedef _Atomic(__char32_t)             atomic_char32_t;
  205 typedef _Atomic(___wchar_t)             atomic_wchar_t;
  206 typedef _Atomic(__int_least8_t)         atomic_int_least8_t;
  207 typedef _Atomic(__uint_least8_t)        atomic_uint_least8_t;
  208 typedef _Atomic(__int_least16_t)        atomic_int_least16_t;
  209 typedef _Atomic(__uint_least16_t)       atomic_uint_least16_t;
  210 typedef _Atomic(__int_least32_t)        atomic_int_least32_t;
  211 typedef _Atomic(__uint_least32_t)       atomic_uint_least32_t;
  212 typedef _Atomic(__int_least64_t)        atomic_int_least64_t;
  213 typedef _Atomic(__uint_least64_t)       atomic_uint_least64_t;
  214 typedef _Atomic(__int_fast8_t)          atomic_int_fast8_t;
  215 typedef _Atomic(__uint_fast8_t)         atomic_uint_fast8_t;
  216 typedef _Atomic(__int_fast16_t)         atomic_int_fast16_t;
  217 typedef _Atomic(__uint_fast16_t)        atomic_uint_fast16_t;
  218 typedef _Atomic(__int_fast32_t)         atomic_int_fast32_t;
  219 typedef _Atomic(__uint_fast32_t)        atomic_uint_fast32_t;
  220 typedef _Atomic(__int_fast64_t)         atomic_int_fast64_t;
  221 typedef _Atomic(__uint_fast64_t)        atomic_uint_fast64_t;
  222 typedef _Atomic(__intptr_t)             atomic_intptr_t;
  223 typedef _Atomic(__uintptr_t)            atomic_uintptr_t;
  224 typedef _Atomic(__size_t)               atomic_size_t;
  225 typedef _Atomic(__ptrdiff_t)            atomic_ptrdiff_t;
  226 typedef _Atomic(__intmax_t)             atomic_intmax_t;
  227 typedef _Atomic(__uintmax_t)            atomic_uintmax_t;
  228 
  229 /*
  230  * 7.17.7 Operations on atomic types.
  231  */
  232 
  233 /*
  234  * Compiler-specific operations.
  235  */
  236 
  237 #if defined(__CLANG_ATOMICS)
  238 #define atomic_compare_exchange_strong_explicit(object, expected,       \
  239     desired, success, failure)                                          \
  240         __c11_atomic_compare_exchange_strong(object, expected, desired, \
  241             success, failure)
  242 #define atomic_compare_exchange_weak_explicit(object, expected,         \
  243     desired, success, failure)                                          \
  244         __c11_atomic_compare_exchange_weak(object, expected, desired,   \
  245             success, failure)
  246 #define atomic_exchange_explicit(object, desired, order)                \
  247         __c11_atomic_exchange(object, desired, order)
  248 #define atomic_fetch_add_explicit(object, operand, order)               \
  249         __c11_atomic_fetch_add(object, operand, order)
  250 #define atomic_fetch_and_explicit(object, operand, order)               \
  251         __c11_atomic_fetch_and(object, operand, order)
  252 #define atomic_fetch_or_explicit(object, operand, order)                \
  253         __c11_atomic_fetch_or(object, operand, order)
  254 #define atomic_fetch_sub_explicit(object, operand, order)               \
  255         __c11_atomic_fetch_sub(object, operand, order)
  256 #define atomic_fetch_xor_explicit(object, operand, order)               \
  257         __c11_atomic_fetch_xor(object, operand, order)
  258 #define atomic_load_explicit(object, order)                             \
  259         __c11_atomic_load(object, order)
  260 #define atomic_store_explicit(object, desired, order)                   \
  261         __c11_atomic_store(object, desired, order)
  262 #elif defined(__GNUC_ATOMICS)
  263 #define atomic_compare_exchange_strong_explicit(object, expected,       \
  264     desired, success, failure)                                          \
  265         __atomic_compare_exchange_n(object, expected,                   \
  266             desired, 0, success, failure)
  267 #define atomic_compare_exchange_weak_explicit(object, expected,         \
  268     desired, success, failure)                                          \
  269         __atomic_compare_exchange_n(object, expected,                   \
  270             desired, 1, success, failure)
  271 #define atomic_exchange_explicit(object, desired, order)                \
  272         __atomic_exchange_n(object, desired, order)
  273 #define atomic_fetch_add_explicit(object, operand, order)               \
  274         __atomic_fetch_add(object, operand, order)
  275 #define atomic_fetch_and_explicit(object, operand, order)               \
  276         __atomic_fetch_and(object, operand, order)
  277 #define atomic_fetch_or_explicit(object, operand, order)                \
  278         __atomic_fetch_or(object, operand, order)
  279 #define atomic_fetch_sub_explicit(object, operand, order)               \
  280         __atomic_fetch_sub(object, operand, order)
  281 #define atomic_fetch_xor_explicit(object, operand, order)               \
  282         __atomic_fetch_xor(object, operand, order)
  283 #define atomic_load_explicit(object, order)                             \
  284         __atomic_load_n(object, order)
  285 #define atomic_store_explicit(object, desired, order)                   \
  286         __atomic_store_n(object, desired, order)
  287 #else
  288 #define __atomic_apply_stride(object, operand) \
  289         (((__typeof__((object)->__val))0) + (operand))
  290 #define atomic_compare_exchange_strong_explicit(object, expected,       \
  291     desired, success, failure)  __extension__ ({                        \
  292         __typeof__(expected) __ep = (expected);                         \
  293         __typeof__(*__ep) __e = *__ep;                                  \
  294         (void)(success); (void)(failure);                               \
  295         (_Bool)((*__ep = __sync_val_compare_and_swap(&(object)->__val,  \
  296             __e, desired)) == __e);                                     \
  297 })
  298 #define atomic_compare_exchange_weak_explicit(object, expected,         \
  299     desired, success, failure)                                          \
  300         atomic_compare_exchange_strong_explicit(object, expected,       \
  301                 desired, success, failure)
  302 #if __has_builtin(__sync_swap)
  303 /* Clang provides a full-barrier atomic exchange - use it if available. */
  304 #define atomic_exchange_explicit(object, desired, order)                \
  305         ((void)(order), __sync_swap(&(object)->__val, desired))
  306 #else
  307 /*
  308  * __sync_lock_test_and_set() is only an acquire barrier in theory (although in
  309  * practice it is usually a full barrier) so we need an explicit barrier before
  310  * it.
  311  */
  312 #define atomic_exchange_explicit(object, desired, order)                \
  313 __extension__ ({                                                        \
  314         __typeof__(object) __o = (object);                              \
  315         __typeof__(desired) __d = (desired);                            \
  316         (void)(order);                                                  \
  317         __sync_synchronize();                                           \
  318         __sync_lock_test_and_set(&(__o)->__val, __d);                   \
  319 })
  320 #endif
  321 #define atomic_fetch_add_explicit(object, operand, order)               \
  322         ((void)(order), __sync_fetch_and_add(&(object)->__val,          \
  323             __atomic_apply_stride(object, operand)))
  324 #define atomic_fetch_and_explicit(object, operand, order)               \
  325         ((void)(order), __sync_fetch_and_and(&(object)->__val, operand))
  326 #define atomic_fetch_or_explicit(object, operand, order)                \
  327         ((void)(order), __sync_fetch_and_or(&(object)->__val, operand))
  328 #define atomic_fetch_sub_explicit(object, operand, order)               \
  329         ((void)(order), __sync_fetch_and_sub(&(object)->__val,          \
  330             __atomic_apply_stride(object, operand)))
  331 #define atomic_fetch_xor_explicit(object, operand, order)               \
  332         ((void)(order), __sync_fetch_and_xor(&(object)->__val, operand))
  333 #define atomic_load_explicit(object, order)                             \
  334         ((void)(order), __sync_fetch_and_add(&(object)->__val, 0))
  335 #define atomic_store_explicit(object, desired, order)                   \
  336         ((void)atomic_exchange_explicit(object, desired, order))
  337 #endif
  338 
  339 /*
  340  * Convenience functions.
  341  *
  342  * Don't provide these in kernel space. In kernel space, we should be
  343  * disciplined enough to always provide explicit barriers.
  344  */
  345 
  346 #ifndef _KERNEL
  347 #define atomic_compare_exchange_strong(object, expected, desired)       \
  348         atomic_compare_exchange_strong_explicit(object, expected,       \
  349             desired, memory_order_seq_cst, memory_order_seq_cst)
  350 #define atomic_compare_exchange_weak(object, expected, desired)         \
  351         atomic_compare_exchange_weak_explicit(object, expected,         \
  352             desired, memory_order_seq_cst, memory_order_seq_cst)
  353 #define atomic_exchange(object, desired)                                \
  354         atomic_exchange_explicit(object, desired, memory_order_seq_cst)
  355 #define atomic_fetch_add(object, operand)                               \
  356         atomic_fetch_add_explicit(object, operand, memory_order_seq_cst)
  357 #define atomic_fetch_and(object, operand)                               \
  358         atomic_fetch_and_explicit(object, operand, memory_order_seq_cst)
  359 #define atomic_fetch_or(object, operand)                                \
  360         atomic_fetch_or_explicit(object, operand, memory_order_seq_cst)
  361 #define atomic_fetch_sub(object, operand)                               \
  362         atomic_fetch_sub_explicit(object, operand, memory_order_seq_cst)
  363 #define atomic_fetch_xor(object, operand)                               \
  364         atomic_fetch_xor_explicit(object, operand, memory_order_seq_cst)
  365 #define atomic_load(object)                                             \
  366         atomic_load_explicit(object, memory_order_seq_cst)
  367 #define atomic_store(object, desired)                                   \
  368         atomic_store_explicit(object, desired, memory_order_seq_cst)
  369 #endif /* !_KERNEL */
  370 
  371 /*
  372  * 7.17.8 Atomic flag type and operations.
  373  *
  374  * XXX: Assume atomic_bool can be used as an atomic_flag. Is there some
  375  * kind of compiler built-in type we could use?
  376  */
  377 
  378 typedef struct {
  379         atomic_bool     __flag;
  380 } atomic_flag;
  381 #define ATOMIC_FLAG_INIT                { ATOMIC_VAR_INIT(0) }
  382 
  383 static __inline _Bool
  384 atomic_flag_test_and_set_explicit(volatile atomic_flag *__object,
  385     memory_order __order)
  386 {
  387         return (atomic_exchange_explicit(&__object->__flag, 1, __order));
  388 }
  389 
  390 static __inline void
  391 atomic_flag_clear_explicit(volatile atomic_flag *__object, memory_order __order)
  392 {
  393 
  394         atomic_store_explicit(&__object->__flag, 0, __order);
  395 }
  396 
  397 #ifndef _KERNEL
  398 static __inline _Bool
  399 atomic_flag_test_and_set(volatile atomic_flag *__object)
  400 {
  401 
  402         return (atomic_flag_test_and_set_explicit(__object,
  403             memory_order_seq_cst));
  404 }
  405 
  406 static __inline void
  407 atomic_flag_clear(volatile atomic_flag *__object)
  408 {
  409 
  410         atomic_flag_clear_explicit(__object, memory_order_seq_cst);
  411 }
  412 #endif /* !_KERNEL */
  413 
  414 #ifdef __bool_locally_defined
  415 #undef _Bool
  416 #undef __bool_locally_defined
  417 #endif
  418 
  419 #endif /* !_STDATOMIC_H_ */

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