Add CMM memory model
[urcu.git] / include / urcu / tls-compat.h
1 // SPDX-FileCopyrightText: 2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
2 //
3 // SPDX-License-Identifier: LGPL-2.1-or-later
4
5 #ifndef _URCU_TLS_COMPAT_H
6 #define _URCU_TLS_COMPAT_H
7
8 /*
9 * Userspace RCU library - Thread-Local Storage Compatibility Header
10 */
11
12 #include <stdlib.h>
13 #include <urcu/config.h>
14 #include <urcu/compiler.h>
15 #include <urcu/arch.h>
16
17 #ifdef __cplusplus
18 extern "C" {
19 #endif
20
21 #ifdef CONFIG_RCU_TLS
22
23 /*
24 * Default to '__thread' on all C and C++ compilers except MSVC. While C11 has
25 * '_Thread_local' and C++11 has 'thread_local', only '__thread' seems to have
26 * a compatible implementation when linking public extern symbols across
27 * language boundaries.
28 *
29 * For more details, see 'https://gcc.gnu.org/onlinedocs/gcc/Thread-Local.html'.
30 */
31 #if defined(_MSC_VER)
32 # define URCU_TLS_STORAGE_CLASS __declspec(thread)
33 #else
34 # define URCU_TLS_STORAGE_CLASS __thread
35 #endif
36
37 /*
38 * Hint: How to define/declare TLS variables of compound types
39 * such as array or function pointers?
40 *
41 * Answer: Use typedef to assign a type_name to the compound type.
42 * Example: Define a TLS variable which is an int array with len=4:
43 *
44 * typedef int my_int_array_type[4];
45 * DEFINE_URCU_TLS(my_int_array_type, var_name);
46 *
47 * Another example:
48 * typedef void (*call_rcu_flavor)(struct rcu_head *, XXXX);
49 * DECLARE_URCU_TLS(call_rcu_flavor, p_call_rcu);
50 *
51 * NOTE: URCU_TLS() is NOT async-signal-safe, you can't use it
52 * inside any function which can be called from signal handler.
53 *
54 * But if pthread_getspecific() is async-signal-safe in your
55 * platform, you can make URCU_TLS() async-signal-safe via:
56 * ensuring the first call to URCU_TLS() of a given TLS variable of
57 * all threads is called earliest from a non-signal handler function.
58 *
59 * Example: In any thread, the first call of URCU_TLS(rcu_reader)
60 * is called from rcu_register_thread(), so we can ensure all later
61 * URCU_TLS(rcu_reader) in any thread is async-signal-safe.
62 *
63 * Moreover, URCU_TLS variables should not be touched from signal
64 * handlers setup with with sigaltstack(2).
65 */
66
67 # define DECLARE_URCU_TLS(type, name) \
68 URCU_TLS_STORAGE_CLASS type name
69
70 # define DEFINE_URCU_TLS(type, name) \
71 URCU_TLS_STORAGE_CLASS type name
72
73 # define DEFINE_URCU_TLS_INIT(type, name, init) \
74 URCU_TLS_STORAGE_CLASS type name = (init)
75
76 # define URCU_TLS(name) (name)
77
78 #else /* #ifndef CONFIG_RCU_TLS */
79
80 /*
81 * The *_1() macros ensure macro parameters are expanded.
82 */
83
84 # include <pthread.h>
85
86 struct urcu_tls {
87 pthread_key_t key;
88 pthread_mutex_t init_mutex;
89 int init_done;
90 };
91
92 # define DECLARE_URCU_TLS_1(type, name) \
93 type *__tls_access_ ## name(void)
94 # define DECLARE_URCU_TLS(type, name) \
95 DECLARE_URCU_TLS_1(type, name)
96
97 /*
98 * Note: we don't free memory at process exit, since it will be dealt
99 * with by the OS.
100 */
101 # define DEFINE_URCU_TLS_INIT_1(type, name, do_init) \
102 type *__tls_access_ ## name(void) \
103 { \
104 static struct urcu_tls __tls_ ## name = { \
105 .key = 0, \
106 .init_mutex = PTHREAD_MUTEX_INITIALIZER,\
107 .init_done = 0, \
108 }; \
109 __typeof__(type) *__tls_p; \
110 if (!__tls_ ## name.init_done) { \
111 /* Mutex to protect concurrent init */ \
112 pthread_mutex_lock(&__tls_ ## name.init_mutex); \
113 if (!__tls_ ## name.init_done) { \
114 (void) pthread_key_create(&__tls_ ## name.key, \
115 free); \
116 cmm_smp_wmb(); /* create key before write init_done */ \
117 __tls_ ## name.init_done = 1; \
118 } \
119 pthread_mutex_unlock(&__tls_ ## name.init_mutex); \
120 } \
121 cmm_smp_rmb(); /* read init_done before getting key */ \
122 __tls_p = (__typeof__(type) *) pthread_getspecific(__tls_ ## name.key); \
123 if (caa_unlikely(__tls_p == NULL)) { \
124 __tls_p = (__typeof__(type) *) calloc(1, sizeof(type)); \
125 do_init \
126 (void) pthread_setspecific(__tls_ ## name.key, \
127 __tls_p); \
128 } \
129 return __tls_p; \
130 }
131
132 # define _URCU_TLS_INIT(init) \
133 *__tls_p = (init);
134
135 # define DEFINE_URCU_TLS_INIT(type, name, init) \
136 DEFINE_URCU_TLS_INIT_1(type, name, _URCU_TLS_INIT(init))
137
138 # define DEFINE_URCU_TLS(type, name) \
139 DEFINE_URCU_TLS_INIT_1(type, name, /* empty */)
140
141 # define URCU_TLS_1(name) (*__tls_access_ ## name())
142
143 # define URCU_TLS(name) URCU_TLS_1(name)
144
145 #endif /* #else #ifndef CONFIG_RCU_TLS */
146
147 #ifdef __cplusplus
148 }
149 #endif
150
151 #endif /* _URCU_TLS_COMPAT_H */
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