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4d0d66bb MD |
1 | #ifndef _URCU_TLS_COMPAT_H |
2 | #define _URCU_TLS_COMPAT_H | |
3 | ||
4 | /* | |
5 | * urcu/tls-compat.h | |
6 | * | |
7 | * Userspace RCU library - Thread-Local Storage Compatibility Header | |
8 | * | |
9 | * Copyright 2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
10 | * | |
11 | * This library is free software; you can redistribute it and/or | |
12 | * modify it under the terms of the GNU Lesser General Public | |
13 | * License as published by the Free Software Foundation; either | |
14 | * version 2.1 of the License, or (at your option) any later version. | |
15 | * | |
16 | * This library is distributed in the hope that it will be useful, | |
17 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
18 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
19 | * Lesser General Public License for more details. | |
20 | * | |
21 | * You should have received a copy of the GNU Lesser General Public | |
22 | * License along with this library; if not, write to the Free Software | |
23 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
24 | */ | |
25 | ||
26 | #include <stdlib.h> | |
27 | #include <urcu/config.h> | |
28 | #include <urcu/compiler.h> | |
29 | #include <urcu/arch.h> | |
30 | ||
31 | #ifdef __cplusplus | |
32 | extern "C" { | |
33 | #endif | |
34 | ||
35 | #ifdef CONFIG_RCU_TLS /* Based on ax_tls.m4 */ | |
36 | ||
c85e62f3 LJ |
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 exmaple: | |
48 | * typedef void (*call_rcu_flavor)(struct rcu_head *, XXXX); | |
49 | * DECLARE_URCU_TLS(call_rcu_flavor, p_call_rcu); | |
fa320ad0 LJ |
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. | |
9948a988 MD |
62 | * |
63 | * Moreover, URCU_TLS variables should not be touched from signal | |
64 | * handlers setup with with sigaltstack(2). | |
c85e62f3 LJ |
65 | */ |
66 | ||
4d0d66bb | 67 | # define DECLARE_URCU_TLS(type, name) \ |
3db1417f | 68 | CONFIG_RCU_TLS type name |
4d0d66bb MD |
69 | |
70 | # define DEFINE_URCU_TLS(type, name) \ | |
3db1417f | 71 | CONFIG_RCU_TLS type name |
4d0d66bb | 72 | |
3db1417f | 73 | # define URCU_TLS(name) (name) |
4d0d66bb MD |
74 | |
75 | #else /* #ifndef CONFIG_RCU_TLS */ | |
76 | ||
77 | # include <pthread.h> | |
78 | ||
79 | struct urcu_tls { | |
80 | pthread_key_t key; | |
81 | pthread_mutex_t init_mutex; | |
82 | int init_done; | |
83 | }; | |
84 | ||
85 | # define DECLARE_URCU_TLS(type, name) \ | |
86 | type *__tls_access_ ## name(void) | |
87 | ||
88 | /* | |
89 | * Note: we don't free memory at process exit, since it will be dealt | |
90 | * with by the OS. | |
91 | */ | |
92 | # define DEFINE_URCU_TLS(type, name) \ | |
93 | type *__tls_access_ ## name(void) \ | |
94 | { \ | |
95 | static struct urcu_tls __tls_ ## name = { \ | |
96 | .init_mutex = PTHREAD_MUTEX_INITIALIZER,\ | |
97 | .init_done = 0, \ | |
98 | }; \ | |
99 | void *__tls_p; \ | |
100 | if (!__tls_ ## name.init_done) { \ | |
101 | /* Mutex to protect concurrent init */ \ | |
102 | pthread_mutex_lock(&__tls_ ## name.init_mutex); \ | |
103 | if (!__tls_ ## name.init_done) { \ | |
104 | (void) pthread_key_create(&__tls_ ## name.key, \ | |
105 | free); \ | |
106 | cmm_smp_wmb(); /* create key before write init_done */ \ | |
107 | __tls_ ## name.init_done = 1; \ | |
108 | } \ | |
109 | pthread_mutex_unlock(&__tls_ ## name.init_mutex); \ | |
110 | } \ | |
111 | cmm_smp_rmb(); /* read init_done before getting key */ \ | |
112 | __tls_p = pthread_getspecific(__tls_ ## name.key); \ | |
113 | if (caa_unlikely(__tls_p == NULL)) { \ | |
114 | __tls_p = calloc(1, sizeof(type)); \ | |
115 | (void) pthread_setspecific(__tls_ ## name.key, \ | |
116 | __tls_p); \ | |
117 | } \ | |
118 | return __tls_p; \ | |
119 | } | |
120 | ||
121 | # define URCU_TLS(name) (*__tls_access_ ## name()) | |
122 | ||
123 | #endif /* #else #ifndef CONFIG_RCU_TLS */ | |
124 | ||
125 | #ifdef __cplusplus | |
126 | } | |
127 | #endif | |
128 | ||
129 | #endif /* _URCU_TLS_COMPAT_H */ |