aboutsummaryrefslogtreecommitdiff
path: root/examples/redis-unstable/src/atomicvar.h
diff options
context:
space:
mode:
Diffstat (limited to 'examples/redis-unstable/src/atomicvar.h')
-rw-r--r--examples/redis-unstable/src/atomicvar.h186
1 files changed, 0 insertions, 186 deletions
diff --git a/examples/redis-unstable/src/atomicvar.h b/examples/redis-unstable/src/atomicvar.h
deleted file mode 100644
index 3c332ee..0000000
--- a/examples/redis-unstable/src/atomicvar.h
+++ /dev/null
@@ -1,186 +0,0 @@
1/* This file implements atomic counters using c11 _Atomic, __atomic or __sync
2 * macros if available, otherwise we will throw an error when compile.
3 *
4 * The exported interface is composed of the following macros:
5 *
6 * atomicIncr(var,count) -- Increment the atomic counter
7 * atomicGetIncr(var,oldvalue_var,count) -- Get and increment the atomic counter
8 * atomicIncrGet(var,newvalue_var,count) -- Increment and get the atomic counter new value
9 * atomicDecr(var,count) -- Decrement the atomic counter
10 * atomicGet(var,dstvar) -- Fetch the atomic counter value
11 * atomicSet(var,value) -- Set the atomic counter value
12 * atomicGetWithSync(var,value) -- 'atomicGet' with inter-thread synchronization
13 * atomicSetWithSync(var,value) -- 'atomicSet' with inter-thread synchronization
14 * atomicCompareExchange(type,var,expected_var,desired) -- Compare and exchange (CAS) operation
15 *
16 * Atomic operations on flags.
17 * Flag type can be int, long, long long or their unsigned counterparts.
18 * The value of the flag can be 1 or 0.
19 *
20 * atomicFlagGetSet(var,oldvalue_var) -- Get and set the atomic counter value
21 *
22 * NOTE1: __atomic* and _Atomic implementations can be actually elaborated to support any value by changing the
23 * hardcoded new value passed to __atomic_exchange* from 1 to @param count
24 * i.e oldvalue_var = atomic_exchange_explicit(&var, count).
25 * However, in order to be compatible with the __sync functions family, we can use only 0 and 1.
26 * The only exchange alternative suggested by __sync is __sync_lock_test_and_set,
27 * But as described by the gnu manual for __sync_lock_test_and_set():
28 * https://gcc.gnu.org/onlinedocs/gcc/_005f_005fsync-Builtins.html
29 * "A target may support reduced functionality here by which the only valid value to store is the immediate constant 1. The exact value
30 * actually stored in *ptr is implementation defined."
31 * Hence, we can't rely on it for a any value other than 1.
32 * We eventually chose to implement this method with __sync_val_compare_and_swap since it satisfies functionality needed for atomicFlagGetSet
33 * (if the flag was 0 -> set to 1, if it's already 1 -> do nothing, but the final result is that the flag is set),
34 * and also it has a full barrier (__sync_lock_test_and_set has acquire barrier).
35 *
36 * NOTE2: Unlike other atomic type, which aren't guaranteed to be lock free, c11 atomic_flag does.
37 * To check whether a type is lock free, atomic_is_lock_free() can be used.
38 * It can be considered to limit the flag type to atomic_flag to improve performance.
39 *
40 * Never use return value from the macros, instead use the AtomicGetIncr()
41 * if you need to get the current value and increment it atomically, like
42 * in the following example:
43 *
44 * long oldvalue;
45 * atomicGetIncr(myvar,oldvalue,1);
46 * doSomethingWith(oldvalue);
47 *
48 * ----------------------------------------------------------------------------
49 *
50 * Copyright (c) 2015-Present, Redis Ltd.
51 * All rights reserved.
52 *
53 * Licensed under your choice of (a) the Redis Source Available License 2.0
54 * (RSALv2); or (b) the Server Side Public License v1 (SSPLv1); or (c) the
55 * GNU Affero General Public License v3 (AGPLv3).
56 */
57
58#include <pthread.h>
59#include "config.h"
60
61#ifndef __ATOMIC_VAR_H
62#define __ATOMIC_VAR_H
63
64/* Define redisAtomic for atomic variable. */
65#define redisAtomic
66
67/* To test Redis with Helgrind (a Valgrind tool) it is useful to define
68 * the following macro, so that __sync macros are used: those can be detected
69 * by Helgrind (even if they are less efficient) so that no false positive
70 * is reported. */
71// #define __ATOMIC_VAR_FORCE_SYNC_MACROS
72
73/* There will be many false positives if we test Redis with Helgrind, since
74 * Helgrind can't understand we have imposed ordering on the program, so
75 * we use macros in helgrind.h to tell Helgrind inter-thread happens-before
76 * relationship explicitly for avoiding false positives.
77 *
78 * For more details, please see: valgrind/helgrind.h and
79 * https://www.valgrind.org/docs/manual/hg-manual.html#hg-manual.effective-use
80 *
81 * These macros take effect only when 'make helgrind', and you must first
82 * install Valgrind in the default path configuration. */
83#ifdef __ATOMIC_VAR_FORCE_SYNC_MACROS
84#include <valgrind/helgrind.h>
85#else
86#define ANNOTATE_HAPPENS_BEFORE(v) ((void) v)
87#define ANNOTATE_HAPPENS_AFTER(v) ((void) v)
88#endif
89
90#if !defined(__ATOMIC_VAR_FORCE_SYNC_MACROS) && defined(__STDC_VERSION__) && \
91 (__STDC_VERSION__ >= 201112L) && !defined(__STDC_NO_ATOMICS__)
92/* Use '_Atomic' keyword if the compiler supports. */
93#undef redisAtomic
94#define redisAtomic _Atomic
95/* Implementation using _Atomic in C11. */
96
97#include <stdatomic.h>
98#define atomicIncr(var,count) atomic_fetch_add_explicit(&var,(count),memory_order_relaxed)
99#define atomicGetIncr(var,oldvalue_var,count) do { \
100 oldvalue_var = atomic_fetch_add_explicit(&var,(count),memory_order_relaxed); \
101} while(0)
102#define atomicIncrGet(var, newvalue_var, count) \
103 newvalue_var = atomicIncr(var,count) + count
104#define atomicDecr(var,count) atomic_fetch_sub_explicit(&var,(count),memory_order_relaxed)
105#define atomicGet(var,dstvar) do { \
106 dstvar = atomic_load_explicit(&var,memory_order_relaxed); \
107} while(0)
108#define atomicSet(var,value) atomic_store_explicit(&var,value,memory_order_relaxed)
109#define atomicGetWithSync(var,dstvar) do { \
110 dstvar = atomic_load_explicit(&var,memory_order_seq_cst); \
111} while(0)
112#define atomicSetWithSync(var,value) \
113 atomic_store_explicit(&var,value,memory_order_seq_cst)
114#define atomicCompareExchange(type,var,expected_var,desired) \
115 atomic_compare_exchange_weak_explicit(&var,&expected_var,desired,memory_order_relaxed,memory_order_relaxed)
116#define atomicFlagGetSet(var,oldvalue_var) \
117 oldvalue_var = atomic_exchange_explicit(&var,1,memory_order_relaxed)
118#define REDIS_ATOMIC_API "c11-builtin"
119
120#elif !defined(__ATOMIC_VAR_FORCE_SYNC_MACROS) && \
121 (!defined(__clang__) || !defined(__APPLE__) || __apple_build_version__ > 4210057) && \
122 defined(__ATOMIC_RELAXED) && defined(__ATOMIC_SEQ_CST)
123/* Implementation using __atomic macros. */
124
125#define atomicIncr(var,count) __atomic_add_fetch(&var,(count),__ATOMIC_RELAXED)
126#define atomicIncrGet(var, newvalue_var, count) \
127 newvalue_var = __atomic_add_fetch(&var,(count),__ATOMIC_RELAXED)
128#define atomicGetIncr(var,oldvalue_var,count) do { \
129 oldvalue_var = __atomic_fetch_add(&var,(count),__ATOMIC_RELAXED); \
130} while(0)
131#define atomicDecr(var,count) __atomic_sub_fetch(&var,(count),__ATOMIC_RELAXED)
132#define atomicGet(var,dstvar) do { \
133 dstvar = __atomic_load_n(&var,__ATOMIC_RELAXED); \
134} while(0)
135#define atomicSet(var,value) __atomic_store_n(&var,value,__ATOMIC_RELAXED)
136#define atomicGetWithSync(var,dstvar) do { \
137 dstvar = __atomic_load_n(&var,__ATOMIC_SEQ_CST); \
138} while(0)
139#define atomicSetWithSync(var,value) \
140 __atomic_store_n(&var,value,__ATOMIC_SEQ_CST)
141#define atomicCompareExchange(type,var,expected_var,desired) \
142 __atomic_compare_exchange_n(&var,&expected_var,desired,1,__ATOMIC_RELAXED,__ATOMIC_RELAXED)
143#define atomicFlagGetSet(var,oldvalue_var) \
144 oldvalue_var = __atomic_exchange_n(&var,1,__ATOMIC_RELAXED)
145#define REDIS_ATOMIC_API "atomic-builtin"
146
147#elif defined(HAVE_ATOMIC)
148/* Implementation using __sync macros. */
149
150#define atomicIncr(var,count) __sync_add_and_fetch(&var,(count))
151#define atomicIncrGet(var, newvalue_var, count) \
152 newvalue_var = __sync_add_and_fetch(&var,(count))
153#define atomicGetIncr(var,oldvalue_var,count) do { \
154 oldvalue_var = __sync_fetch_and_add(&var,(count)); \
155} while(0)
156#define atomicDecr(var,count) __sync_sub_and_fetch(&var,(count))
157#define atomicGet(var,dstvar) do { \
158 dstvar = __sync_sub_and_fetch(&var,0); \
159} while(0)
160#define atomicSet(var,value) do { \
161 while(!__sync_bool_compare_and_swap(&var,var,value)); \
162} while(0)
163/* Actually the builtin issues a full memory barrier by default. */
164#define atomicGetWithSync(var,dstvar) do { \
165 dstvar = __sync_sub_and_fetch(&var,0,__sync_synchronize); \
166 ANNOTATE_HAPPENS_AFTER(&var); \
167} while(0)
168#define atomicSetWithSync(var,value) do { \
169 ANNOTATE_HAPPENS_BEFORE(&var); \
170 while(!__sync_bool_compare_and_swap(&var,var,value,__sync_synchronize)); \
171} while(0)
172#define atomicCompareExchange(type,var,expected_var,desired) ({ \
173 type _old = __sync_val_compare_and_swap(&var,expected_var,desired); \
174 int _success = (_old == expected_var); \
175 if (!_success) expected_var = _old; \
176 _success; \
177})
178#define atomicFlagGetSet(var,oldvalue_var) \
179 oldvalue_var = __sync_val_compare_and_swap(&var,0,1)
180#define REDIS_ATOMIC_API "sync-builtin"
181
182#else
183#error "Unable to determine atomic operations for your platform"
184
185#endif
186#endif /* __ATOMIC_VAR_H */