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generic-gcc.h
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1 /*-------------------------------------------------------------------------
2  *
3  * generic-gcc.h
4  * Atomic operations, implemented using gcc (or compatible) intrinsics.
5  *
6  * Portions Copyright (c) 1996-2017, 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  * http://gcc.gnu.org/onlinedocs/gcc-4.8.2/gcc/_005f_005fsync-Builtins.html
14  * * Built-in functions for memory model aware atomic operations
15  * http://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 4.1.0 or higher, 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 (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 1))
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() __atomic_thread_fence(__ATOMIC_ACQUIRE)
48 #endif
49 
50 #if !defined(pg_write_barrier_impl) && defined(HAVE_GCC__ATOMIC_INT32_CAS)
51 /* release semantics include write barrier semantics */
52 # define pg_write_barrier_impl() __atomic_thread_fence(__ATOMIC_RELEASE)
53 #endif
54 
55 
56 #ifdef HAVE_ATOMICS
57 
58 /* generic gcc based atomic flag implementation */
59 #if !defined(PG_HAVE_ATOMIC_FLAG_SUPPORT) \
60  && (defined(HAVE_GCC__SYNC_INT32_TAS) || defined(HAVE_GCC__SYNC_CHAR_TAS))
61 
62 #define PG_HAVE_ATOMIC_FLAG_SUPPORT
63 typedef struct pg_atomic_flag
64 {
65  /*
66  * If we have a choice, use int-width TAS, because that is more efficient
67  * and/or more reliably implemented on most non-Intel platforms. (Note
68  * that this code isn't used on x86[_64]; see arch-x86.h for that.)
69  */
70 #ifdef HAVE_GCC__SYNC_INT32_TAS
71  volatile int value;
72 #else
73  volatile char value;
74 #endif
76 
77 #endif /* !ATOMIC_FLAG_SUPPORT && SYNC_INT32_TAS */
78 
79 /* generic gcc based atomic uint32 implementation */
80 #if !defined(PG_HAVE_ATOMIC_U32_SUPPORT) \
81  && (defined(HAVE_GCC__ATOMIC_INT32_CAS) || defined(HAVE_GCC__SYNC_INT32_CAS))
82 
83 #define PG_HAVE_ATOMIC_U32_SUPPORT
84 typedef struct pg_atomic_uint32
85 {
86  volatile uint32 value;
88 
89 #endif /* defined(HAVE_GCC__ATOMIC_INT32_CAS) || defined(HAVE_GCC__SYNC_INT32_CAS) */
90 
91 /* generic gcc based atomic uint64 implementation */
92 #if !defined(PG_HAVE_ATOMIC_U64_SUPPORT) \
93  && !defined(PG_DISABLE_64_BIT_ATOMICS) \
94  && (defined(HAVE_GCC__ATOMIC_INT64_CAS) || defined(HAVE_GCC__SYNC_INT64_CAS))
95 
96 #define PG_HAVE_ATOMIC_U64_SUPPORT
97 
98 typedef struct pg_atomic_uint64
99 {
100  volatile uint64 value pg_attribute_aligned(8);
102 
103 #endif /* defined(HAVE_GCC__ATOMIC_INT64_CAS) || defined(HAVE_GCC__SYNC_INT64_CAS) */
104 
105 #ifdef PG_HAVE_ATOMIC_FLAG_SUPPORT
106 
107 #if defined(HAVE_GCC__SYNC_CHAR_TAS) || defined(HAVE_GCC__SYNC_INT32_TAS)
108 
109 #ifndef PG_HAVE_ATOMIC_TEST_SET_FLAG
110 #define PG_HAVE_ATOMIC_TEST_SET_FLAG
111 static inline bool
113 {
114  /* NB: only an acquire barrier, not a full one */
115  /* some platform only support a 1 here */
116  return __sync_lock_test_and_set(&ptr->value, 1) == 0;
117 }
118 #endif
119 
120 #endif /* defined(HAVE_GCC__SYNC_*_TAS) */
121 
122 #ifndef PG_HAVE_ATOMIC_UNLOCKED_TEST_FLAG
123 #define PG_HAVE_ATOMIC_UNLOCKED_TEST_FLAG
124 static inline bool
126 {
127  return ptr->value == 0;
128 }
129 #endif
130 
131 #ifndef PG_HAVE_ATOMIC_CLEAR_FLAG
132 #define PG_HAVE_ATOMIC_CLEAR_FLAG
133 static inline void
135 {
136  __sync_lock_release(&ptr->value);
137 }
138 #endif
139 
140 #ifndef PG_HAVE_ATOMIC_INIT_FLAG
141 #define PG_HAVE_ATOMIC_INIT_FLAG
142 static inline void
144 {
146 }
147 #endif
148 
149 #endif /* defined(PG_HAVE_ATOMIC_FLAG_SUPPORT) */
150 
151 /* prefer __atomic, it has a better API */
152 #if !defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U32) && defined(HAVE_GCC__ATOMIC_INT32_CAS)
153 #define PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U32
154 static inline bool
156  uint32 *expected, uint32 newval)
157 {
158  /* FIXME: we can probably use a lower consistency model */
159  return __atomic_compare_exchange_n(&ptr->value, expected, newval, false,
160  __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
161 }
162 #endif
163 
164 #if !defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U32) && defined(HAVE_GCC__SYNC_INT32_CAS)
165 #define PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U32
166 static inline bool
168  uint32 *expected, uint32 newval)
169 {
170  bool ret;
171  uint32 current;
172  current = __sync_val_compare_and_swap(&ptr->value, *expected, newval);
173  ret = current == *expected;
174  *expected = current;
175  return ret;
176 }
177 #endif
178 
179 #if !defined(PG_HAVE_ATOMIC_FETCH_ADD_U32) && defined(HAVE_GCC__SYNC_INT32_CAS)
180 #define PG_HAVE_ATOMIC_FETCH_ADD_U32
181 static inline uint32
183 {
184  return __sync_fetch_and_add(&ptr->value, add_);
185 }
186 #endif
187 
188 
189 #if !defined(PG_DISABLE_64_BIT_ATOMICS)
190 
191 #if !defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U64) && defined(HAVE_GCC__ATOMIC_INT64_CAS)
192 #define PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U64
193 static inline bool
195  uint64 *expected, uint64 newval)
196 {
197  return __atomic_compare_exchange_n(&ptr->value, expected, newval, false,
198  __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
199 }
200 #endif
201 
202 #if !defined(PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U64) && defined(HAVE_GCC__SYNC_INT64_CAS)
203 #define PG_HAVE_ATOMIC_COMPARE_EXCHANGE_U64
204 static inline bool
206  uint64 *expected, uint64 newval)
207 {
208  bool ret;
209  uint64 current;
210  current = __sync_val_compare_and_swap(&ptr->value, *expected, newval);
211  ret = current == *expected;
212  *expected = current;
213  return ret;
214 }
215 #endif
216 
217 #if !defined(PG_HAVE_ATOMIC_FETCH_ADD_U64) && defined(HAVE_GCC__SYNC_INT64_CAS)
218 #define PG_HAVE_ATOMIC_FETCH_ADD_U64
219 static inline uint64
220 pg_atomic_fetch_add_u64_impl(volatile pg_atomic_uint64 *ptr, int64 add_)
221 {
222  return __sync_fetch_and_add(&ptr->value, add_);
223 }
224 #endif
225 
226 #endif /* !defined(PG_DISABLE_64_BIT_ATOMICS) */
227 
228 #endif /* defined(HAVE_ATOMICS) */
struct pg_atomic_flag pg_atomic_flag
struct pg_atomic_uint32 pg_atomic_uint32
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
struct pg_atomic_uint64 pg_atomic_uint64
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:256
uint32 pg_atomic_fetch_add_u32_impl(volatile pg_atomic_uint32 *ptr, int32 add_)
Definition: atomics.c:148
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:268
volatile uint64 value
Definition: fallback.h:118
void pg_atomic_init_flag_impl(volatile pg_atomic_flag *ptr)
Definition: atomics.c:55
#define newval
bool pg_atomic_test_set_flag_impl(volatile pg_atomic_flag *ptr)
Definition: atomics.c:74
static bool pg_atomic_unlocked_test_flag_impl(volatile pg_atomic_flag *ptr)
Definition: fallback.h:136