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generic.h
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1 /*-------------------------------------------------------------------------
2  *
3  * generic.h
4  * Implement higher level operations based on some lower level atomic
5  * operations.
6  *
7  * Portions Copyright (c) 1996-2017, 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
41 #endif
42 
43 #ifndef PG_HAVE_ATOMIC_READ_U32
44 #define PG_HAVE_ATOMIC_READ_U32
45 static inline uint32
47 {
48  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
56 {
57  ptr->value = val;
58 }
59 #endif
60 
61 #ifndef PG_HAVE_ATOMIC_UNLOCKED_WRITE_U32
62 #define PG_HAVE_ATOMIC_UNLOCKED_WRITE_U32
63 static inline void
65 {
66  ptr->value = val;
67 }
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
78 {
80 }
81 
82 #define PG_HAVE_ATOMIC_TEST_SET_FLAG
83 static inline bool
85 {
86  return pg_atomic_exchange_u32_impl(ptr, &value, 1) == 0;
87 }
88 
89 #define PG_HAVE_ATOMIC_UNLOCKED_TEST_FLAG
90 static inline bool
92 {
93  return pg_atomic_read_u32_impl(ptr) == 0;
94 }
95 
96 
97 #define PG_HAVE_ATOMIC_CLEAR_FLAG
98 static inline void
100 {
101  /* XXX: release semantics suffice? */
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
115 {
116  pg_atomic_write_u32_impl(ptr, 0);
117 }
118 
119 #define PG_HAVE_ATOMIC_TEST_SET_FLAG
120 static inline bool
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
130 {
131  return pg_atomic_read_u32_impl(ptr) == 0;
132 }
133 
134 #define PG_HAVE_ATOMIC_CLEAR_FLAG
135 static inline void
137 {
138  /*
139  * Use a memory barrier + plain write if we have a native memory
140  * barrier. But don't do so if memory barriers use spinlocks - that'd lead
141  * to circularity if flags are used to implement spinlocks.
142  */
143 #ifndef PG_HAVE_MEMORY_BARRIER_EMULATION
144  /* XXX: release semantics suffice? */
146  pg_atomic_write_u32_impl(ptr, 0);
147 #else
148  uint32 value = 1;
149  pg_atomic_compare_exchange_u32_impl(ptr, &value, 0);
150 #endif
151 }
152 
153 #elif !defined(PG_HAVE_ATOMIC_TEST_SET_FLAG)
154 # error "No pg_atomic_test_and_set provided"
155 #endif /* !defined(PG_HAVE_ATOMIC_TEST_SET_FLAG) */
156 
157 
158 #ifndef PG_HAVE_ATOMIC_INIT_U32
159 #define PG_HAVE_ATOMIC_INIT_U32
160 static inline void
162 {
163  pg_atomic_write_u32_impl(ptr, val_);
164 }
165 #endif
166 
167 #if !defined(PG_HAVE_ATOMIC_EXCHANGE_U32) && defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U32)
168 #define PG_HAVE_ATOMIC_EXCHANGE_U32
169 static inline uint32
170 pg_atomic_exchange_u32_impl(volatile pg_atomic_uint32 *ptr, uint32 xchg_)
171 {
172  uint32 old;
173  old = ptr->value; /* ok if read is not atomic */
174  while (!pg_atomic_compare_exchange_u32_impl(ptr, &old, xchg_))
175  /* skip */;
176  return old;
177 }
178 #endif
179 
180 #if !defined(PG_HAVE_ATOMIC_FETCH_ADD_U32) && defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U32)
181 #define PG_HAVE_ATOMIC_FETCH_ADD_U32
182 static inline uint32
184 {
185  uint32 old;
186  old = ptr->value; /* ok if read is not atomic */
187  while (!pg_atomic_compare_exchange_u32_impl(ptr, &old, old + add_))
188  /* skip */;
189  return old;
190 }
191 #endif
192 
193 #if !defined(PG_HAVE_ATOMIC_FETCH_SUB_U32) && defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U32)
194 #define PG_HAVE_ATOMIC_FETCH_SUB_U32
195 static inline uint32
196 pg_atomic_fetch_sub_u32_impl(volatile pg_atomic_uint32 *ptr, int32 sub_)
197 {
198  return pg_atomic_fetch_add_u32_impl(ptr, -sub_);
199 }
200 #endif
201 
202 #if !defined(PG_HAVE_ATOMIC_FETCH_AND_U32) && defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U32)
203 #define PG_HAVE_ATOMIC_FETCH_AND_U32
204 static inline uint32
205 pg_atomic_fetch_and_u32_impl(volatile pg_atomic_uint32 *ptr, uint32 and_)
206 {
207  uint32 old;
208  old = ptr->value; /* ok if read is not atomic */
209  while (!pg_atomic_compare_exchange_u32_impl(ptr, &old, old & and_))
210  /* skip */;
211  return old;
212 }
213 #endif
214 
215 #if !defined(PG_HAVE_ATOMIC_FETCH_OR_U32) && defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U32)
216 #define PG_HAVE_ATOMIC_FETCH_OR_U32
217 static inline uint32
218 pg_atomic_fetch_or_u32_impl(volatile pg_atomic_uint32 *ptr, uint32 or_)
219 {
220  uint32 old;
221  old = ptr->value; /* ok if read is not atomic */
222  while (!pg_atomic_compare_exchange_u32_impl(ptr, &old, old | or_))
223  /* skip */;
224  return old;
225 }
226 #endif
227 
228 #if !defined(PG_HAVE_ATOMIC_ADD_FETCH_U32) && defined(PG_HAVE_ATOMIC_FETCH_ADD_U32)
229 #define PG_HAVE_ATOMIC_ADD_FETCH_U32
230 static inline uint32
231 pg_atomic_add_fetch_u32_impl(volatile pg_atomic_uint32 *ptr, int32 add_)
232 {
233  return pg_atomic_fetch_add_u32_impl(ptr, add_) + add_;
234 }
235 #endif
236 
237 #if !defined(PG_HAVE_ATOMIC_SUB_FETCH_U32) && defined(PG_HAVE_ATOMIC_FETCH_SUB_U32)
238 #define PG_HAVE_ATOMIC_SUB_FETCH_U32
239 static inline uint32
240 pg_atomic_sub_fetch_u32_impl(volatile pg_atomic_uint32 *ptr, int32 sub_)
241 {
242  return pg_atomic_fetch_sub_u32_impl(ptr, sub_) - sub_;
243 }
244 #endif
245 
246 #if !defined(PG_HAVE_ATOMIC_EXCHANGE_U64) && defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U64)
247 #define PG_HAVE_ATOMIC_EXCHANGE_U64
248 static inline uint64
249 pg_atomic_exchange_u64_impl(volatile pg_atomic_uint64 *ptr, uint64 xchg_)
250 {
251  uint64 old;
252  old = ptr->value; /* ok if read is not atomic */
253  while (!pg_atomic_compare_exchange_u64_impl(ptr, &old, xchg_))
254  /* skip */;
255  return old;
256 }
257 #endif
258 
259 #ifndef PG_HAVE_ATOMIC_WRITE_U64
260 #define PG_HAVE_ATOMIC_WRITE_U64
261 
262 #if defined(PG_HAVE_8BYTE_SINGLE_COPY_ATOMICITY) && \
263  !defined(PG_HAVE_ATOMIC_U64_SIMULATION)
264 
265 static inline void
266 pg_atomic_write_u64_impl(volatile pg_atomic_uint64 *ptr, uint64 val)
267 {
268  /*
269  * On this platform aligned 64bit writes are guaranteed to be atomic,
270  * except if using the fallback implementation, where can't guarantee the
271  * required alignment.
272  */
273  AssertPointerAlignment(ptr, 8);
274  ptr->value = val;
275 }
276 
277 #else
278 
279 static inline void
281 {
282  /*
283  * 64 bit writes aren't safe on all platforms. In the generic
284  * implementation implement them as an atomic exchange.
285  */
286  pg_atomic_exchange_u64_impl(ptr, val);
287 }
288 
289 #endif /* PG_HAVE_8BYTE_SINGLE_COPY_ATOMICITY && !PG_HAVE_ATOMIC_U64_SIMULATION */
290 #endif /* PG_HAVE_ATOMIC_WRITE_U64 */
291 
292 #ifndef PG_HAVE_ATOMIC_READ_U64
293 #define PG_HAVE_ATOMIC_READ_U64
294 
295 #if defined(PG_HAVE_8BYTE_SINGLE_COPY_ATOMICITY) && \
296  !defined(PG_HAVE_ATOMIC_U64_SIMULATION)
297 
298 static inline uint64
300 {
301  /*
302  * On this platform aligned 64-bit reads are guaranteed to be atomic.
303  */
304  AssertPointerAlignment(ptr, 8);
305  return ptr->value;
306 }
307 
308 #else
309 
310 static inline uint64
312 {
313  uint64 old = 0;
314 
315  /*
316  * 64-bit reads aren't atomic on all platforms. In the generic
317  * implementation implement them as a compare/exchange with 0. That'll
318  * fail or succeed, but always return the old value. Possibly might store
319  * a 0, but only if the previous value also was a 0 - i.e. harmless.
320  */
322 
323  return old;
324 }
325 #endif /* PG_HAVE_8BYTE_SINGLE_COPY_ATOMICITY && !PG_HAVE_ATOMIC_U64_SIMULATION */
326 #endif /* PG_HAVE_ATOMIC_READ_U64 */
327 
328 #ifndef PG_HAVE_ATOMIC_INIT_U64
329 #define PG_HAVE_ATOMIC_INIT_U64
330 static inline void
331 pg_atomic_init_u64_impl(volatile pg_atomic_uint64 *ptr, uint64 val_)
332 {
333  pg_atomic_write_u64_impl(ptr, val_);
334 }
335 #endif
336 
337 #if !defined(PG_HAVE_ATOMIC_FETCH_ADD_U64) && defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U64)
338 #define PG_HAVE_ATOMIC_FETCH_ADD_U64
339 static inline uint64
340 pg_atomic_fetch_add_u64_impl(volatile pg_atomic_uint64 *ptr, int64 add_)
341 {
342  uint64 old;
343  old = ptr->value; /* ok if read is not atomic */
344  while (!pg_atomic_compare_exchange_u64_impl(ptr, &old, old + add_))
345  /* skip */;
346  return old;
347 }
348 #endif
349 
350 #if !defined(PG_HAVE_ATOMIC_FETCH_SUB_U64) && defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U64)
351 #define PG_HAVE_ATOMIC_FETCH_SUB_U64
352 static inline uint64
353 pg_atomic_fetch_sub_u64_impl(volatile pg_atomic_uint64 *ptr, int64 sub_)
354 {
355  return pg_atomic_fetch_add_u64_impl(ptr, -sub_);
356 }
357 #endif
358 
359 #if !defined(PG_HAVE_ATOMIC_FETCH_AND_U64) && defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U64)
360 #define PG_HAVE_ATOMIC_FETCH_AND_U64
361 static inline uint64
362 pg_atomic_fetch_and_u64_impl(volatile pg_atomic_uint64 *ptr, uint64 and_)
363 {
364  uint64 old;
365  old = ptr->value; /* ok if read is not atomic */
366  while (!pg_atomic_compare_exchange_u64_impl(ptr, &old, old & and_))
367  /* skip */;
368  return old;
369 }
370 #endif
371 
372 #if !defined(PG_HAVE_ATOMIC_FETCH_OR_U64) && defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U64)
373 #define PG_HAVE_ATOMIC_FETCH_OR_U64
374 static inline uint64
375 pg_atomic_fetch_or_u64_impl(volatile pg_atomic_uint64 *ptr, uint64 or_)
376 {
377  uint64 old;
378  old = ptr->value; /* ok if read is not atomic */
379  while (!pg_atomic_compare_exchange_u64_impl(ptr, &old, old | or_))
380  /* skip */;
381  return old;
382 }
383 #endif
384 
385 #if !defined(PG_HAVE_ATOMIC_ADD_FETCH_U64) && defined(PG_HAVE_ATOMIC_FETCH_ADD_U64)
386 #define PG_HAVE_ATOMIC_ADD_FETCH_U64
387 static inline uint64
388 pg_atomic_add_fetch_u64_impl(volatile pg_atomic_uint64 *ptr, int64 add_)
389 {
390  return pg_atomic_fetch_add_u64_impl(ptr, add_) + add_;
391 }
392 #endif
393 
394 #if !defined(PG_HAVE_ATOMIC_SUB_FETCH_U64) && defined(PG_HAVE_ATOMIC_FETCH_SUB_U64)
395 #define PG_HAVE_ATOMIC_SUB_FETCH_U64
396 static inline uint64
397 pg_atomic_sub_fetch_u64_impl(volatile pg_atomic_uint64 *ptr, int64 sub_)
398 {
399  return pg_atomic_fetch_sub_u64_impl(ptr, sub_) - sub_;
400 }
401 #endif
static uint32 pg_atomic_read_u32_impl(volatile pg_atomic_uint32 *ptr)
Definition: generic.h:46
static void pg_atomic_init_u64_impl(volatile pg_atomic_uint64 *ptr, uint64 val_)
Definition: generic.h:331
struct pg_atomic_flag pg_atomic_flag
static void pg_atomic_unlocked_write_u32_impl(volatile pg_atomic_uint32 *ptr, uint32 val)
Definition: generic.h:64
bool pg_atomic_compare_exchange_u64_impl(volatile pg_atomic_uint64 *ptr, uint64 *expected, uint64 newval)
Definition: atomics.c:183
void pg_atomic_clear_flag_impl(volatile pg_atomic_flag *ptr)
Definition: atomics.c:80
bool pg_atomic_compare_exchange_u32_impl(volatile pg_atomic_uint32 *ptr, uint32 *expected, uint32 newval)
Definition: atomics.c:120
volatile uint32 value
Definition: fallback.h:100
signed int int32
Definition: c.h:246
uint32 pg_atomic_fetch_add_u32_impl(volatile pg_atomic_uint32 *ptr, int32 add_)
Definition: atomics.c:148
static void pg_atomic_write_u32_impl(volatile pg_atomic_uint32 *ptr, uint32 val)
Definition: generic.h:55
static struct @121 value
uint64 pg_atomic_fetch_add_u64_impl(volatile pg_atomic_uint64 *ptr, int64 add_)
Definition: atomics.c:211
unsigned int uint32
Definition: c.h:258
volatile uint64 value
Definition: fallback.h:118
void pg_atomic_init_flag_impl(volatile pg_atomic_flag *ptr)
Definition: atomics.c:55
#define AssertPointerAlignment(ptr, bndr)
Definition: c.h:685
static void pg_atomic_init_u32_impl(volatile pg_atomic_uint32 *ptr, uint32 val_)
Definition: generic.h:161
#define pg_memory_barrier_impl()
Definition: arch-hppa.h:17
static void pg_atomic_write_u64_impl(volatile pg_atomic_uint64 *ptr, uint64 val)
Definition: generic.h:280
bool pg_atomic_test_set_flag_impl(volatile pg_atomic_flag *ptr)
Definition: atomics.c:74
long val
Definition: informix.c:689
static bool pg_atomic_unlocked_test_flag_impl(volatile pg_atomic_flag *ptr)
Definition: fallback.h:136
static uint64 pg_atomic_read_u64_impl(volatile pg_atomic_uint64 *ptr)
Definition: generic.h:311