include/urcu/tls-compat.h

   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
  36
  37 #if defined (__cplusplus) && (__cplusplus >= 201103L)
  38 # define URCU_TLS_STORAGE_CLASS thread_local
  39 #elif defined (__STDC_VERSION__) && (__STDC_VERSION__ >= 201112L)
  40 # define URCU_TLS_STORAGE_CLASS _Thread_local
  41 #elif defined (_MSC_VER)
  42 # define URCU_TLS_STORAGE_CLASS __declspec(thread)
  43 #else
  44 # define URCU_TLS_STORAGE_CLASS __thread
  45 #endif
  46
  47 /*
  48  * Hint: How to define/declare TLS variables of compound types
  49  *       such as array or function pointers?
  50  *
  51  * Answer: Use typedef to assign a type_name to the compound type.
  52  * Example: Define a TLS variable which is an int array with len=4:
  53  *
  54  *      typedef int my_int_array_type[4];
  55  *      DEFINE_URCU_TLS(my_int_array_type, var_name);
  56  *
  57  * Another example:
  58  *      typedef void (*call_rcu_flavor)(struct rcu_head *, XXXX);
  59  *      DECLARE_URCU_TLS(call_rcu_flavor, p_call_rcu);
  60  *
  61  * NOTE: URCU_TLS() is NOT async-signal-safe, you can't use it
  62  * inside any function which can be called from signal handler.
  63  *
  64  * But if pthread_getspecific() is async-signal-safe in your
  65  * platform, you can make URCU_TLS() async-signal-safe via:
  66  * ensuring the first call to URCU_TLS() of a given TLS variable of
  67  * all threads is called earliest from a non-signal handler function.
  68  *
  69  * Example: In any thread, the first call of URCU_TLS(rcu_reader)
  70  * is called from rcu_register_thread(), so we can ensure all later
  71  * URCU_TLS(rcu_reader) in any thread is async-signal-safe.
  72  *
  73  * Moreover, URCU_TLS variables should not be touched from signal
  74  * handlers setup with with sigaltstack(2).
  75  */
  76
  77 # define DECLARE_URCU_TLS(type, name)   \
  78         URCU_TLS_STORAGE_CLASS type name
  79
  80 # define DEFINE_URCU_TLS(type, name)    \
  81         URCU_TLS_STORAGE_CLASS type name
  82
  83 # define DEFINE_URCU_TLS_INIT(type, name, init) \
  84         URCU_TLS_STORAGE_CLASS type name = (init)
  85
  86 # define URCU_TLS(name)         (name)
  87
  88 #else /* #ifndef CONFIG_RCU_TLS */
  89
  90 /*
  91  * The *_1() macros ensure macro parameters are expanded.
  92  */
  93
  94 # include <pthread.h>
  95
  96 struct urcu_tls {
  97         pthread_key_t key;
  98         pthread_mutex_t init_mutex;
  99         int init_done;
 100 };
 101
 102 # define DECLARE_URCU_TLS_1(type, name)                         \
 103         type *__tls_access_ ## name(void)
 104 # define DECLARE_URCU_TLS(type, name)                           \
 105         DECLARE_URCU_TLS_1(type, name)
 106
 107 /*
 108  * Note: we don't free memory at process exit, since it will be dealt
 109  * with by the OS.
 110  */
 111 # define DEFINE_URCU_TLS_INIT_1(type, name, do_init)            \
 112         type *__tls_access_ ## name(void)                       \
 113         {                                                       \
 114                 static struct urcu_tls __tls_ ## name = {       \
 115                         .init_mutex = PTHREAD_MUTEX_INITIALIZER,\
 116                         .init_done = 0,                         \
 117                 };                                              \
 118                 __typeof__(type) *__tls_p;                      \
 119                 if (!__tls_ ## name.init_done) {                \
 120                         /* Mutex to protect concurrent init */  \
 121                         pthread_mutex_lock(&__tls_ ## name.init_mutex); \
 122                         if (!__tls_ ## name.init_done) {        \
 123                                 (void) pthread_key_create(&__tls_ ## name.key, \
 124                                         free);                  \
 125                                 cmm_smp_wmb();  /* create key before write init_done */ \
 126                                 __tls_ ## name.init_done = 1;   \
 127                         }                                       \
 128                         pthread_mutex_unlock(&__tls_ ## name.init_mutex); \
 129                 }                                               \
 130                 cmm_smp_rmb();  /* read init_done before getting key */ \
 131                 __tls_p = pthread_getspecific(__tls_ ## name.key); \
 132                 if (caa_unlikely(__tls_p == NULL)) {            \
 133                         __tls_p = calloc(1, sizeof(type));      \
 134                         do_init                                 \
 135                         (void) pthread_setspecific(__tls_ ## name.key,  \
 136                                 __tls_p);                       \
 137                 }                                               \
 138                 return __tls_p;                                 \
 139         }
 140
 141 # define _URCU_TLS_INIT(init)                                   \
 142         *__tls_p = (init);
 143
 144 # define DEFINE_URCU_TLS_INIT(type, name, init)                 \
 145         DEFINE_URCU_TLS_INIT_1(type, name, _URCU_TLS_INIT(init))
 146
 147 # define DEFINE_URCU_TLS(type, name)                            \
 148         DEFINE_URCU_TLS_INIT_1(type, name, /* empty */)
 149
 150 # define URCU_TLS_1(name)       (*__tls_access_ ## name())
 151
 152 # define URCU_TLS(name)         URCU_TLS_1(name)
 153
 154 #endif  /* #else #ifndef CONFIG_RCU_TLS */
 155
 156 #ifdef __cplusplus
 157 }
 158 #endif
 159
 160 #endif /* _URCU_TLS_COMPAT_H */