Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * generic.h
4 : * Implement higher level operations based on some lower level atomic
5 : * operations.
6 : *
7 : * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
8 : * Portions Copyright (c) 1994, Regents of the University of California
9 : *
10 : * src/include/port/atomics/generic.h
11 : *
12 : *-------------------------------------------------------------------------
13 : */
14 :
15 : /* intentionally no include guards, should only be included by atomics.h */
16 : #ifndef INSIDE_ATOMICS_H
17 : # error "should be included via atomics.h"
18 : #endif
19 :
20 : /*
21 : * If read or write barriers are undefined, we upgrade them to full memory
22 : * barriers.
23 : */
24 : #if !defined(pg_read_barrier_impl)
25 : # define pg_read_barrier_impl pg_memory_barrier_impl
26 : #endif
27 : #if !defined(pg_write_barrier_impl)
28 : # define pg_write_barrier_impl pg_memory_barrier_impl
29 : #endif
30 :
31 : #ifndef PG_HAVE_SPIN_DELAY
32 : #define PG_HAVE_SPIN_DELAY
33 : #define pg_spin_delay_impl() ((void)0)
34 : #endif
35 :
36 :
37 : /* provide fallback */
38 : #if !defined(PG_HAVE_ATOMIC_FLAG_SUPPORT) && defined(PG_HAVE_ATOMIC_U32_SUPPORT)
39 : #define PG_HAVE_ATOMIC_FLAG_SUPPORT
40 : typedef pg_atomic_uint32 pg_atomic_flag;
41 : #endif
42 :
43 : #ifndef PG_HAVE_ATOMIC_READ_U32
44 : #define PG_HAVE_ATOMIC_READ_U32
45 : static inline uint32
46 1078062620 : pg_atomic_read_u32_impl(volatile pg_atomic_uint32 *ptr)
47 : {
48 1078062620 : return ptr->value;
49 : }
50 : #endif
51 :
52 : #ifndef PG_HAVE_ATOMIC_WRITE_U32
53 : #define PG_HAVE_ATOMIC_WRITE_U32
54 : static inline void
55 75529572 : pg_atomic_write_u32_impl(volatile pg_atomic_uint32 *ptr, uint32 val)
56 : {
57 75529572 : ptr->value = val;
58 75529572 : }
59 : #endif
60 :
61 : #ifndef PG_HAVE_ATOMIC_UNLOCKED_WRITE_U32
62 : #define PG_HAVE_ATOMIC_UNLOCKED_WRITE_U32
63 : static inline void
64 8699228 : pg_atomic_unlocked_write_u32_impl(volatile pg_atomic_uint32 *ptr, uint32 val)
65 : {
66 8699228 : ptr->value = val;
67 8699228 : }
68 : #endif
69 :
70 : /*
71 : * provide fallback for test_and_set using atomic_exchange if available
72 : */
73 : #if !defined(PG_HAVE_ATOMIC_TEST_SET_FLAG) && defined(PG_HAVE_ATOMIC_EXCHANGE_U32)
74 :
75 : #define PG_HAVE_ATOMIC_INIT_FLAG
76 : static inline void
77 : pg_atomic_init_flag_impl(volatile pg_atomic_flag *ptr)
78 : {
79 : pg_atomic_write_u32_impl(ptr, 0);
80 : }
81 :
82 : #define PG_HAVE_ATOMIC_TEST_SET_FLAG
83 : static inline bool
84 : pg_atomic_test_set_flag_impl(volatile pg_atomic_flag *ptr)
85 : {
86 : return pg_atomic_exchange_u32_impl(ptr, 1) == 0;
87 : }
88 :
89 : #define PG_HAVE_ATOMIC_UNLOCKED_TEST_FLAG
90 : static inline bool
91 : pg_atomic_unlocked_test_flag_impl(volatile pg_atomic_flag *ptr)
92 : {
93 : return pg_atomic_read_u32_impl(ptr) == 0;
94 : }
95 :
96 :
97 : #define PG_HAVE_ATOMIC_CLEAR_FLAG
98 : static inline void
99 : pg_atomic_clear_flag_impl(volatile pg_atomic_flag *ptr)
100 : {
101 : /* XXX: release semantics suffice? */
102 : pg_memory_barrier_impl();
103 : pg_atomic_write_u32_impl(ptr, 0);
104 : }
105 :
106 : /*
107 : * provide fallback for test_and_set using atomic_compare_exchange if
108 : * available.
109 : */
110 : #elif !defined(PG_HAVE_ATOMIC_TEST_SET_FLAG) && defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U32)
111 :
112 : #define PG_HAVE_ATOMIC_INIT_FLAG
113 : static inline void
114 : pg_atomic_init_flag_impl(volatile pg_atomic_flag *ptr)
115 : {
116 : pg_atomic_write_u32_impl(ptr, 0);
117 : }
118 :
119 : #define PG_HAVE_ATOMIC_TEST_SET_FLAG
120 : static inline bool
121 : pg_atomic_test_set_flag_impl(volatile pg_atomic_flag *ptr)
122 : {
123 : uint32 value = 0;
124 : return pg_atomic_compare_exchange_u32_impl(ptr, &value, 1);
125 : }
126 :
127 : #define PG_HAVE_ATOMIC_UNLOCKED_TEST_FLAG
128 : static inline bool
129 : pg_atomic_unlocked_test_flag_impl(volatile pg_atomic_flag *ptr)
130 : {
131 : return pg_atomic_read_u32_impl(ptr) == 0;
132 : }
133 :
134 : #define PG_HAVE_ATOMIC_CLEAR_FLAG
135 : static inline void
136 : pg_atomic_clear_flag_impl(volatile pg_atomic_flag *ptr)
137 : {
138 : /* XXX: release semantics suffice? */
139 : pg_memory_barrier_impl();
140 : pg_atomic_write_u32_impl(ptr, 0);
141 : }
142 :
143 : #elif !defined(PG_HAVE_ATOMIC_TEST_SET_FLAG)
144 : # error "No pg_atomic_test_and_set provided"
145 : #endif /* !defined(PG_HAVE_ATOMIC_TEST_SET_FLAG) */
146 :
147 :
148 : #ifndef PG_HAVE_ATOMIC_INIT_U32
149 : #define PG_HAVE_ATOMIC_INIT_U32
150 : static inline void
151 47345224 : pg_atomic_init_u32_impl(volatile pg_atomic_uint32 *ptr, uint32 val_)
152 : {
153 47345224 : ptr->value = val_;
154 47345224 : }
155 : #endif
156 :
157 : #if !defined(PG_HAVE_ATOMIC_EXCHANGE_U32) && defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U32)
158 : #define PG_HAVE_ATOMIC_EXCHANGE_U32
159 : static inline uint32
160 : pg_atomic_exchange_u32_impl(volatile pg_atomic_uint32 *ptr, uint32 xchg_)
161 : {
162 : uint32 old;
163 : old = ptr->value; /* ok if read is not atomic */
164 : while (!pg_atomic_compare_exchange_u32_impl(ptr, &old, xchg_))
165 : /* skip */;
166 : return old;
167 : }
168 : #endif
169 :
170 : #if !defined(PG_HAVE_ATOMIC_FETCH_ADD_U32) && defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U32)
171 : #define PG_HAVE_ATOMIC_FETCH_ADD_U32
172 : static inline uint32
173 : pg_atomic_fetch_add_u32_impl(volatile pg_atomic_uint32 *ptr, int32 add_)
174 : {
175 : uint32 old;
176 : old = ptr->value; /* ok if read is not atomic */
177 : while (!pg_atomic_compare_exchange_u32_impl(ptr, &old, old + add_))
178 : /* skip */;
179 : return old;
180 : }
181 : #endif
182 :
183 : #if !defined(PG_HAVE_ATOMIC_FETCH_SUB_U32) && defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U32)
184 : #define PG_HAVE_ATOMIC_FETCH_SUB_U32
185 : static inline uint32
186 : pg_atomic_fetch_sub_u32_impl(volatile pg_atomic_uint32 *ptr, int32 sub_)
187 : {
188 : return pg_atomic_fetch_add_u32_impl(ptr, -sub_);
189 : }
190 : #endif
191 :
192 : #if !defined(PG_HAVE_ATOMIC_FETCH_AND_U32) && defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U32)
193 : #define PG_HAVE_ATOMIC_FETCH_AND_U32
194 : static inline uint32
195 : pg_atomic_fetch_and_u32_impl(volatile pg_atomic_uint32 *ptr, uint32 and_)
196 : {
197 : uint32 old;
198 : old = ptr->value; /* ok if read is not atomic */
199 : while (!pg_atomic_compare_exchange_u32_impl(ptr, &old, old & and_))
200 : /* skip */;
201 : return old;
202 : }
203 : #endif
204 :
205 : #if !defined(PG_HAVE_ATOMIC_FETCH_OR_U32) && defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U32)
206 : #define PG_HAVE_ATOMIC_FETCH_OR_U32
207 : static inline uint32
208 : pg_atomic_fetch_or_u32_impl(volatile pg_atomic_uint32 *ptr, uint32 or_)
209 : {
210 : uint32 old;
211 : old = ptr->value; /* ok if read is not atomic */
212 : while (!pg_atomic_compare_exchange_u32_impl(ptr, &old, old | or_))
213 : /* skip */;
214 : return old;
215 : }
216 : #endif
217 :
218 : #if !defined(PG_HAVE_ATOMIC_ADD_FETCH_U32) && defined(PG_HAVE_ATOMIC_FETCH_ADD_U32)
219 : #define PG_HAVE_ATOMIC_ADD_FETCH_U32
220 : static inline uint32
221 804 : pg_atomic_add_fetch_u32_impl(volatile pg_atomic_uint32 *ptr, int32 add_)
222 : {
223 804 : return pg_atomic_fetch_add_u32_impl(ptr, add_) + add_;
224 : }
225 : #endif
226 :
227 : #if !defined(PG_HAVE_ATOMIC_SUB_FETCH_U32) && defined(PG_HAVE_ATOMIC_FETCH_SUB_U32)
228 : #define PG_HAVE_ATOMIC_SUB_FETCH_U32
229 : static inline uint32
230 720016158 : pg_atomic_sub_fetch_u32_impl(volatile pg_atomic_uint32 *ptr, int32 sub_)
231 : {
232 720016158 : return pg_atomic_fetch_sub_u32_impl(ptr, sub_) - sub_;
233 : }
234 : #endif
235 :
236 : #if !defined(PG_HAVE_ATOMIC_READ_MEMBARRIER_U32) && defined(PG_HAVE_ATOMIC_FETCH_ADD_U32)
237 : #define PG_HAVE_ATOMIC_READ_MEMBARRIER_U32
238 : static inline uint32
239 : pg_atomic_read_membarrier_u32_impl(volatile pg_atomic_uint32 *ptr)
240 : {
241 : return pg_atomic_fetch_add_u32_impl(ptr, 0);
242 : }
243 : #endif
244 :
245 : #if !defined(PG_HAVE_ATOMIC_WRITE_MEMBARRIER_U32) && defined(PG_HAVE_ATOMIC_EXCHANGE_U32)
246 : #define PG_HAVE_ATOMIC_WRITE_MEMBARRIER_U32
247 : static inline void
248 28 : pg_atomic_write_membarrier_u32_impl(volatile pg_atomic_uint32 *ptr, uint32 val)
249 : {
250 28 : (void) pg_atomic_exchange_u32_impl(ptr, val);
251 28 : }
252 : #endif
253 :
254 : #if !defined(PG_HAVE_ATOMIC_EXCHANGE_U64) && defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U64)
255 : #define PG_HAVE_ATOMIC_EXCHANGE_U64
256 : static inline uint64
257 : pg_atomic_exchange_u64_impl(volatile pg_atomic_uint64 *ptr, uint64 xchg_)
258 : {
259 : uint64 old;
260 : old = ptr->value; /* ok if read is not atomic */
261 : while (!pg_atomic_compare_exchange_u64_impl(ptr, &old, xchg_))
262 : /* skip */;
263 : return old;
264 : }
265 : #endif
266 :
267 : #ifndef PG_HAVE_ATOMIC_WRITE_U64
268 : #define PG_HAVE_ATOMIC_WRITE_U64
269 :
270 : #if defined(PG_HAVE_8BYTE_SINGLE_COPY_ATOMICITY) && \
271 : !defined(PG_HAVE_ATOMIC_U64_SIMULATION)
272 :
273 : static inline void
274 38965114 : pg_atomic_write_u64_impl(volatile pg_atomic_uint64 *ptr, uint64 val)
275 : {
276 : /*
277 : * On this platform aligned 64bit writes are guaranteed to be atomic,
278 : * except if using the fallback implementation, where can't guarantee the
279 : * required alignment.
280 : */
281 : AssertPointerAlignment(ptr, 8);
282 38965114 : ptr->value = val;
283 38965114 : }
284 :
285 : #else
286 :
287 : static inline void
288 : pg_atomic_write_u64_impl(volatile pg_atomic_uint64 *ptr, uint64 val)
289 : {
290 : /*
291 : * 64 bit writes aren't safe on all platforms. In the generic
292 : * implementation implement them as an atomic exchange.
293 : */
294 : pg_atomic_exchange_u64_impl(ptr, val);
295 : }
296 :
297 : #endif /* PG_HAVE_8BYTE_SINGLE_COPY_ATOMICITY && !PG_HAVE_ATOMIC_U64_SIMULATION */
298 : #endif /* PG_HAVE_ATOMIC_WRITE_U64 */
299 :
300 : #ifndef PG_HAVE_ATOMIC_READ_U64
301 : #define PG_HAVE_ATOMIC_READ_U64
302 :
303 : #if defined(PG_HAVE_8BYTE_SINGLE_COPY_ATOMICITY) && \
304 : !defined(PG_HAVE_ATOMIC_U64_SIMULATION)
305 :
306 : static inline uint64
307 574129354 : pg_atomic_read_u64_impl(volatile pg_atomic_uint64 *ptr)
308 : {
309 : /*
310 : * On this platform aligned 64-bit reads are guaranteed to be atomic.
311 : */
312 : AssertPointerAlignment(ptr, 8);
313 574129354 : return ptr->value;
314 : }
315 :
316 : #else
317 :
318 : static inline uint64
319 : pg_atomic_read_u64_impl(volatile pg_atomic_uint64 *ptr)
320 : {
321 : uint64 old = 0;
322 :
323 : /*
324 : * 64-bit reads aren't atomic on all platforms. In the generic
325 : * implementation implement them as a compare/exchange with 0. That'll
326 : * fail or succeed, but always return the old value. Possibly might store
327 : * a 0, but only if the previous value also was a 0 - i.e. harmless.
328 : */
329 : pg_atomic_compare_exchange_u64_impl(ptr, &old, 0);
330 :
331 : return old;
332 : }
333 : #endif /* PG_HAVE_8BYTE_SINGLE_COPY_ATOMICITY && !PG_HAVE_ATOMIC_U64_SIMULATION */
334 : #endif /* PG_HAVE_ATOMIC_READ_U64 */
335 :
336 : #ifndef PG_HAVE_ATOMIC_INIT_U64
337 : #define PG_HAVE_ATOMIC_INIT_U64
338 : static inline void
339 5676764 : pg_atomic_init_u64_impl(volatile pg_atomic_uint64 *ptr, uint64 val_)
340 : {
341 5676764 : ptr->value = val_;
342 5676764 : }
343 : #endif
344 :
345 : #if !defined(PG_HAVE_ATOMIC_FETCH_ADD_U64) && defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U64)
346 : #define PG_HAVE_ATOMIC_FETCH_ADD_U64
347 : static inline uint64
348 : pg_atomic_fetch_add_u64_impl(volatile pg_atomic_uint64 *ptr, int64 add_)
349 : {
350 : uint64 old;
351 : old = ptr->value; /* ok if read is not atomic */
352 : while (!pg_atomic_compare_exchange_u64_impl(ptr, &old, old + add_))
353 : /* skip */;
354 : return old;
355 : }
356 : #endif
357 :
358 : #if !defined(PG_HAVE_ATOMIC_FETCH_SUB_U64) && defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U64)
359 : #define PG_HAVE_ATOMIC_FETCH_SUB_U64
360 : static inline uint64
361 : pg_atomic_fetch_sub_u64_impl(volatile pg_atomic_uint64 *ptr, int64 sub_)
362 : {
363 : return pg_atomic_fetch_add_u64_impl(ptr, -sub_);
364 : }
365 : #endif
366 :
367 : #if !defined(PG_HAVE_ATOMIC_FETCH_AND_U64) && defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U64)
368 : #define PG_HAVE_ATOMIC_FETCH_AND_U64
369 : static inline uint64
370 : pg_atomic_fetch_and_u64_impl(volatile pg_atomic_uint64 *ptr, uint64 and_)
371 : {
372 : uint64 old;
373 : old = ptr->value; /* ok if read is not atomic */
374 : while (!pg_atomic_compare_exchange_u64_impl(ptr, &old, old & and_))
375 : /* skip */;
376 : return old;
377 : }
378 : #endif
379 :
380 : #if !defined(PG_HAVE_ATOMIC_FETCH_OR_U64) && defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U64)
381 : #define PG_HAVE_ATOMIC_FETCH_OR_U64
382 : static inline uint64
383 : pg_atomic_fetch_or_u64_impl(volatile pg_atomic_uint64 *ptr, uint64 or_)
384 : {
385 : uint64 old;
386 : old = ptr->value; /* ok if read is not atomic */
387 : while (!pg_atomic_compare_exchange_u64_impl(ptr, &old, old | or_))
388 : /* skip */;
389 : return old;
390 : }
391 : #endif
392 :
393 : #if !defined(PG_HAVE_ATOMIC_ADD_FETCH_U64) && defined(PG_HAVE_ATOMIC_FETCH_ADD_U64)
394 : #define PG_HAVE_ATOMIC_ADD_FETCH_U64
395 : static inline uint64
396 188 : pg_atomic_add_fetch_u64_impl(volatile pg_atomic_uint64 *ptr, int64 add_)
397 : {
398 188 : return pg_atomic_fetch_add_u64_impl(ptr, add_) + add_;
399 : }
400 : #endif
401 :
402 : #if !defined(PG_HAVE_ATOMIC_SUB_FETCH_U64) && defined(PG_HAVE_ATOMIC_FETCH_SUB_U64)
403 : #define PG_HAVE_ATOMIC_SUB_FETCH_U64
404 : static inline uint64
405 6 : pg_atomic_sub_fetch_u64_impl(volatile pg_atomic_uint64 *ptr, int64 sub_)
406 : {
407 6 : return pg_atomic_fetch_sub_u64_impl(ptr, sub_) - sub_;
408 : }
409 : #endif
410 :
411 : #if !defined(PG_HAVE_ATOMIC_READ_MEMBARRIER_U64) && defined(PG_HAVE_ATOMIC_FETCH_ADD_U64)
412 : #define PG_HAVE_ATOMIC_READ_MEMBARRIER_U64
413 : static inline uint64
414 3975180 : pg_atomic_read_membarrier_u64_impl(volatile pg_atomic_uint64 *ptr)
415 : {
416 3975180 : return pg_atomic_fetch_add_u64_impl(ptr, 0);
417 : }
418 : #endif
419 :
420 : #if !defined(PG_HAVE_ATOMIC_WRITE_MEMBARRIER_U64) && defined(PG_HAVE_ATOMIC_EXCHANGE_U64)
421 : #define PG_HAVE_ATOMIC_WRITE_MEMBARRIER_U64
422 : static inline void
423 1812 : pg_atomic_write_membarrier_u64_impl(volatile pg_atomic_uint64 *ptr, uint64 val)
424 : {
425 1812 : (void) pg_atomic_exchange_u64_impl(ptr, val);
426 1812 : }
427 : #endif
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