Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * generic-gcc.h
4 : * Atomic operations, implemented using gcc (or compatible) intrinsics.
5 : *
6 : * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
7 : * Portions Copyright (c) 1994, Regents of the University of California
8 : *
9 : * NOTES:
10 : *
11 : * Documentation:
12 : * * Legacy __sync Built-in Functions for Atomic Memory Access
13 : * https://gcc.gnu.org/onlinedocs/gcc-4.8.2/gcc/_005f_005fsync-Builtins.html
14 : * * Built-in functions for memory model aware atomic operations
15 : * https://gcc.gnu.org/onlinedocs/gcc-4.8.2/gcc/_005f_005fatomic-Builtins.html
16 : *
17 : * src/include/port/atomics/generic-gcc.h
18 : *
19 : *-------------------------------------------------------------------------
20 : */
21 :
22 : /* intentionally no include guards, should only be included by atomics.h */
23 : #ifndef INSIDE_ATOMICS_H
24 : #error "should be included via atomics.h"
25 : #endif
26 :
27 : /*
28 : * An empty asm block should be a sufficient compiler barrier.
29 : */
30 : #define pg_compiler_barrier_impl() __asm__ __volatile__("" ::: "memory")
31 :
32 : /*
33 : * If we're on GCC, we should be able to get a memory barrier
34 : * out of this compiler built-in. But we prefer to rely on platform specific
35 : * definitions where possible, and use this only as a fallback.
36 : */
37 : #if !defined(pg_memory_barrier_impl)
38 : # if defined(HAVE_GCC__ATOMIC_INT32_CAS)
39 : # define pg_memory_barrier_impl() __atomic_thread_fence(__ATOMIC_SEQ_CST)
40 : # elif defined(__GNUC__)
41 : # define pg_memory_barrier_impl() __sync_synchronize()
42 : # endif
43 : #endif /* !defined(pg_memory_barrier_impl) */
44 :
45 : #if !defined(pg_read_barrier_impl) && defined(HAVE_GCC__ATOMIC_INT32_CAS)
46 : /* acquire semantics include read barrier semantics */
47 : # define pg_read_barrier_impl() do \
48 : { \
49 : pg_compiler_barrier_impl(); \
50 : __atomic_thread_fence(__ATOMIC_ACQUIRE); \
51 : } while (0)
52 : #endif
53 :
54 : #if !defined(pg_write_barrier_impl) && defined(HAVE_GCC__ATOMIC_INT32_CAS)
55 : /* release semantics include write barrier semantics */
56 : # define pg_write_barrier_impl() do \
57 : { \
58 : pg_compiler_barrier_impl(); \
59 : __atomic_thread_fence(__ATOMIC_RELEASE); \
60 : } while (0)
61 : #endif
62 :
63 :
64 : /* generic gcc based atomic flag implementation */
65 : #if !defined(PG_HAVE_ATOMIC_FLAG_SUPPORT) \
66 : && (defined(HAVE_GCC__SYNC_INT32_TAS) || defined(HAVE_GCC__SYNC_CHAR_TAS))
67 :
68 : #define PG_HAVE_ATOMIC_FLAG_SUPPORT
69 : typedef struct pg_atomic_flag
70 : {
71 : /*
72 : * If we have a choice, use int-width TAS, because that is more efficient
73 : * and/or more reliably implemented on most non-Intel platforms. (Note
74 : * that this code isn't used on x86[_64]; see arch-x86.h for that.)
75 : */
76 : #ifdef HAVE_GCC__SYNC_INT32_TAS
77 : volatile int value;
78 : #else
79 : volatile char value;
80 : #endif
81 : } pg_atomic_flag;
82 :
83 : #endif /* !ATOMIC_FLAG_SUPPORT && SYNC_INT32_TAS */
84 :
85 : /* generic gcc based atomic uint32 implementation */
86 : #if !defined(PG_HAVE_ATOMIC_U32_SUPPORT) \
87 : && (defined(HAVE_GCC__ATOMIC_INT32_CAS) || defined(HAVE_GCC__SYNC_INT32_CAS))
88 :
89 : #define PG_HAVE_ATOMIC_U32_SUPPORT
90 : typedef struct pg_atomic_uint32
91 : {
92 : volatile uint32 value;
93 : } pg_atomic_uint32;
94 :
95 : #endif /* defined(HAVE_GCC__ATOMIC_INT32_CAS) || defined(HAVE_GCC__SYNC_INT32_CAS) */
96 :
97 : /* generic gcc based atomic uint64 implementation */
98 : #if !defined(PG_HAVE_ATOMIC_U64_SUPPORT) \
99 : && !defined(PG_DISABLE_64_BIT_ATOMICS) \
100 : && (defined(HAVE_GCC__ATOMIC_INT64_CAS) || defined(HAVE_GCC__SYNC_INT64_CAS))
101 :
102 : #define PG_HAVE_ATOMIC_U64_SUPPORT
103 : typedef struct pg_atomic_uint64
104 : {
105 : alignas(8) volatile uint64 value;
106 : } pg_atomic_uint64;
107 :
108 : #endif /* defined(HAVE_GCC__ATOMIC_INT64_CAS) || defined(HAVE_GCC__SYNC_INT64_CAS) */
109 :
110 : #ifdef PG_HAVE_ATOMIC_FLAG_SUPPORT
111 :
112 : #if defined(HAVE_GCC__SYNC_CHAR_TAS) || defined(HAVE_GCC__SYNC_INT32_TAS)
113 :
114 : #ifndef PG_HAVE_ATOMIC_TEST_SET_FLAG
115 : #define PG_HAVE_ATOMIC_TEST_SET_FLAG
116 : static inline bool
117 : pg_atomic_test_set_flag_impl(volatile pg_atomic_flag *ptr)
118 : {
119 : /* NB: only an acquire barrier, not a full one */
120 : /* some platform only support a 1 here */
121 : return __sync_lock_test_and_set(&ptr->value, 1) == 0;
122 : }
123 : #endif
124 :
125 : #endif /* defined(HAVE_GCC__SYNC_*_TAS) */
126 :
127 : #ifndef PG_HAVE_ATOMIC_UNLOCKED_TEST_FLAG
128 : #define PG_HAVE_ATOMIC_UNLOCKED_TEST_FLAG
129 : static inline bool
130 785406 : pg_atomic_unlocked_test_flag_impl(volatile pg_atomic_flag *ptr)
131 : {
132 785406 : return ptr->value == 0;
133 : }
134 : #endif
135 :
136 : #ifndef PG_HAVE_ATOMIC_CLEAR_FLAG
137 : #define PG_HAVE_ATOMIC_CLEAR_FLAG
138 : static inline void
139 : pg_atomic_clear_flag_impl(volatile pg_atomic_flag *ptr)
140 : {
141 : __sync_lock_release(&ptr->value);
142 : }
143 : #endif
144 :
145 : #ifndef PG_HAVE_ATOMIC_INIT_FLAG
146 : #define PG_HAVE_ATOMIC_INIT_FLAG
147 : static inline void
148 24206 : pg_atomic_init_flag_impl(volatile pg_atomic_flag *ptr)
149 : {
150 24206 : pg_atomic_clear_flag_impl(ptr);
151 24206 : }
152 : #endif
153 :
154 : #endif /* defined(PG_HAVE_ATOMIC_FLAG_SUPPORT) */
155 :
156 : /* prefer __atomic, it has a better API */
157 : #if !defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U32) && defined(HAVE_GCC__ATOMIC_INT32_CAS)
158 : #define PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U32
159 : static inline bool
160 : pg_atomic_compare_exchange_u32_impl(volatile pg_atomic_uint32 *ptr,
161 : uint32 *expected, uint32 newval)
162 : {
163 : /* FIXME: we can probably use a lower consistency model */
164 : return __atomic_compare_exchange_n(&ptr->value, expected, newval, false,
165 : __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
166 : }
167 : #endif
168 :
169 : #if !defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U32) && defined(HAVE_GCC__SYNC_INT32_CAS)
170 : #define PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U32
171 : static inline bool
172 : pg_atomic_compare_exchange_u32_impl(volatile pg_atomic_uint32 *ptr,
173 : uint32 *expected, uint32 newval)
174 : {
175 : bool ret;
176 : uint32 current;
177 : current = __sync_val_compare_and_swap(&ptr->value, *expected, newval);
178 : ret = current == *expected;
179 : *expected = current;
180 : return ret;
181 : }
182 : #endif
183 :
184 : /*
185 : * __sync_lock_test_and_set() only supports setting the value to 1 on some
186 : * platforms, so we only provide an __atomic implementation for
187 : * pg_atomic_exchange.
188 : *
189 : * We assume the availability of 32-bit __atomic_compare_exchange_n() implies
190 : * the availability of 32-bit __atomic_exchange_n().
191 : */
192 : #if !defined(PG_HAVE_ATOMIC_EXCHANGE_U32) && defined(HAVE_GCC__ATOMIC_INT32_CAS)
193 : #define PG_HAVE_ATOMIC_EXCHANGE_U32
194 : static inline uint32
195 29702 : pg_atomic_exchange_u32_impl(volatile pg_atomic_uint32 *ptr, uint32 newval)
196 : {
197 29702 : return __atomic_exchange_n(&ptr->value, newval, __ATOMIC_SEQ_CST);
198 : }
199 : #endif
200 :
201 : /* if we have 32-bit __sync_val_compare_and_swap, assume we have these too: */
202 :
203 : #if !defined(PG_HAVE_ATOMIC_FETCH_ADD_U32) && defined(HAVE_GCC__SYNC_INT32_CAS)
204 : #define PG_HAVE_ATOMIC_FETCH_ADD_U32
205 : static inline uint32
206 : pg_atomic_fetch_add_u32_impl(volatile pg_atomic_uint32 *ptr, int32 add_)
207 : {
208 : return __sync_fetch_and_add(&ptr->value, add_);
209 : }
210 : #endif
211 :
212 : #if !defined(PG_HAVE_ATOMIC_FETCH_SUB_U32) && defined(HAVE_GCC__SYNC_INT32_CAS)
213 : #define PG_HAVE_ATOMIC_FETCH_SUB_U32
214 : static inline uint32
215 882646052 : pg_atomic_fetch_sub_u32_impl(volatile pg_atomic_uint32 *ptr, int32 sub_)
216 : {
217 882646052 : return __sync_fetch_and_sub(&ptr->value, sub_);
218 : }
219 : #endif
220 :
221 : #if !defined(PG_HAVE_ATOMIC_FETCH_AND_U32) && defined(HAVE_GCC__SYNC_INT32_CAS)
222 : #define PG_HAVE_ATOMIC_FETCH_AND_U32
223 : static inline uint32
224 8582898 : pg_atomic_fetch_and_u32_impl(volatile pg_atomic_uint32 *ptr, uint32 and_)
225 : {
226 8582898 : return __sync_fetch_and_and(&ptr->value, and_);
227 : }
228 : #endif
229 :
230 : #if !defined(PG_HAVE_ATOMIC_FETCH_OR_U32) && defined(HAVE_GCC__SYNC_INT32_CAS)
231 : #define PG_HAVE_ATOMIC_FETCH_OR_U32
232 : static inline uint32
233 80030994 : pg_atomic_fetch_or_u32_impl(volatile pg_atomic_uint32 *ptr, uint32 or_)
234 : {
235 80030994 : return __sync_fetch_and_or(&ptr->value, or_);
236 : }
237 : #endif
238 :
239 :
240 : #if !defined(PG_DISABLE_64_BIT_ATOMICS)
241 :
242 : #if !defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U64) && defined(HAVE_GCC__ATOMIC_INT64_CAS)
243 : #define PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U64
244 : static inline bool
245 : pg_atomic_compare_exchange_u64_impl(volatile pg_atomic_uint64 *ptr,
246 : uint64 *expected, uint64 newval)
247 : {
248 : AssertPointerAlignment(expected, 8);
249 : return __atomic_compare_exchange_n(&ptr->value, expected, newval, false,
250 : __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
251 : }
252 : #endif
253 :
254 : #if !defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U64) && defined(HAVE_GCC__SYNC_INT64_CAS)
255 : #define PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U64
256 : static inline bool
257 : pg_atomic_compare_exchange_u64_impl(volatile pg_atomic_uint64 *ptr,
258 : uint64 *expected, uint64 newval)
259 : {
260 : bool ret;
261 : uint64 current;
262 :
263 : AssertPointerAlignment(expected, 8);
264 : current = __sync_val_compare_and_swap(&ptr->value, *expected, newval);
265 : ret = current == *expected;
266 : *expected = current;
267 : return ret;
268 : }
269 : #endif
270 :
271 : /*
272 : * __sync_lock_test_and_set() only supports setting the value to 1 on some
273 : * platforms, so we only provide an __atomic implementation for
274 : * pg_atomic_exchange.
275 : *
276 : * We assume the availability of 64-bit __atomic_compare_exchange_n() implies
277 : * the availability of 64-bit __atomic_exchange_n().
278 : */
279 : #if !defined(PG_HAVE_ATOMIC_EXCHANGE_U64) && defined(HAVE_GCC__ATOMIC_INT64_CAS)
280 : #define PG_HAVE_ATOMIC_EXCHANGE_U64
281 : static inline uint64
282 34611174 : pg_atomic_exchange_u64_impl(volatile pg_atomic_uint64 *ptr, uint64 newval)
283 : {
284 34611174 : return __atomic_exchange_n(&ptr->value, newval, __ATOMIC_SEQ_CST);
285 : }
286 : #endif
287 :
288 : /* if we have 64-bit __sync_val_compare_and_swap, assume we have these too: */
289 :
290 : #if !defined(PG_HAVE_ATOMIC_FETCH_ADD_U64) && defined(HAVE_GCC__SYNC_INT64_CAS)
291 : #define PG_HAVE_ATOMIC_FETCH_ADD_U64
292 : static inline uint64
293 : pg_atomic_fetch_add_u64_impl(volatile pg_atomic_uint64 *ptr, int64 add_)
294 : {
295 : return __sync_fetch_and_add(&ptr->value, add_);
296 : }
297 : #endif
298 :
299 : #if !defined(PG_HAVE_ATOMIC_FETCH_SUB_U64) && defined(HAVE_GCC__SYNC_INT64_CAS)
300 : #define PG_HAVE_ATOMIC_FETCH_SUB_U64
301 : static inline uint64
302 14 : pg_atomic_fetch_sub_u64_impl(volatile pg_atomic_uint64 *ptr, int64 sub_)
303 : {
304 14 : return __sync_fetch_and_sub(&ptr->value, sub_);
305 : }
306 : #endif
307 :
308 : #if !defined(PG_HAVE_ATOMIC_FETCH_AND_U64) && defined(HAVE_GCC__SYNC_INT64_CAS)
309 : #define PG_HAVE_ATOMIC_FETCH_AND_U64
310 : static inline uint64
311 18 : pg_atomic_fetch_and_u64_impl(volatile pg_atomic_uint64 *ptr, uint64 and_)
312 : {
313 18 : return __sync_fetch_and_and(&ptr->value, and_);
314 : }
315 : #endif
316 :
317 : #if !defined(PG_HAVE_ATOMIC_FETCH_OR_U64) && defined(HAVE_GCC__SYNC_INT64_CAS)
318 : #define PG_HAVE_ATOMIC_FETCH_OR_U64
319 : static inline uint64
320 12 : pg_atomic_fetch_or_u64_impl(volatile pg_atomic_uint64 *ptr, uint64 or_)
321 : {
322 12 : return __sync_fetch_and_or(&ptr->value, or_);
323 : }
324 : #endif
325 :
326 : #endif /* !defined(PG_DISABLE_64_BIT_ATOMICS) */
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