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 /*
  38  * Don't use C++ 'thread_local' on MacOs, the implementation is incompatible
  39  * with C and will result in a link error when accessing an extern variable
  40  * provided by the C library from C++ code.
  41  */
  42 #if defined (__cplusplus) && (__cplusplus >= 201103L) && !defined(__APPLE__)
  43 # define URCU_TLS_STORAGE_CLASS thread_local
  44 #elif defined (__STDC_VERSION__) && (__STDC_VERSION__ >= 201112L)
  45 # define URCU_TLS_STORAGE_CLASS _Thread_local
  46 #elif defined (_MSC_VER)
  47 # define URCU_TLS_STORAGE_CLASS __declspec(thread)
  48 #else
  49 # define URCU_TLS_STORAGE_CLASS __thread
  50 #endif
  51
  52 /*
  53  * Hint: How to define/declare TLS variables of compound types
  54  *       such as array or function pointers?
  55  *
  56  * Answer: Use typedef to assign a type_name to the compound type.
  57  * Example: Define a TLS variable which is an int array with len=4:
  58  *
  59  *      typedef int my_int_array_type[4];
  60  *      DEFINE_URCU_TLS(my_int_array_type, var_name);
  61  *
  62  * Another example:
  63  *      typedef void (*call_rcu_flavor)(struct rcu_head *, XXXX);
  64  *      DECLARE_URCU_TLS(call_rcu_flavor, p_call_rcu);
  65  *
  66  * NOTE: URCU_TLS() is NOT async-signal-safe, you can't use it
  67  * inside any function which can be called from signal handler.
  68  *
  69  * But if pthread_getspecific() is async-signal-safe in your
  70  * platform, you can make URCU_TLS() async-signal-safe via:
  71  * ensuring the first call to URCU_TLS() of a given TLS variable of
  72  * all threads is called earliest from a non-signal handler function.
  73  *
  74  * Example: In any thread, the first call of URCU_TLS(rcu_reader)
  75  * is called from rcu_register_thread(), so we can ensure all later
  76  * URCU_TLS(rcu_reader) in any thread is async-signal-safe.
  77  *
  78  * Moreover, URCU_TLS variables should not be touched from signal
  79  * handlers setup with with sigaltstack(2).
  80  */
  81
  82 # define DECLARE_URCU_TLS(type, name)   \
  83         URCU_TLS_STORAGE_CLASS type name
  84
  85 # define DEFINE_URCU_TLS(type, name)    \
  86         URCU_TLS_STORAGE_CLASS type name
  87
  88 # define DEFINE_URCU_TLS_INIT(type, name, init) \
  89         URCU_TLS_STORAGE_CLASS type name = (init)
  90
  91 # define URCU_TLS(name)         (name)
  92
  93 #else /* #ifndef CONFIG_RCU_TLS */
  94
  95 /*
  96  * The *_1() macros ensure macro parameters are expanded.
  97  */
  98
  99 # include <pthread.h>
 100
 101 struct urcu_tls {
 102         pthread_key_t key;
 103         pthread_mutex_t init_mutex;
 104         int init_done;
 105 };
 106
 107 # define DECLARE_URCU_TLS_1(type, name)                         \
 108         type *__tls_access_ ## name(void)
 109 # define DECLARE_URCU_TLS(type, name)                           \
 110         DECLARE_URCU_TLS_1(type, name)
 111
 112 /*
 113  * Note: we don't free memory at process exit, since it will be dealt
 114  * with by the OS.
 115  */
 116 # define DEFINE_URCU_TLS_INIT_1(type, name, do_init)            \
 117         type *__tls_access_ ## name(void)                       \
 118         {                                                       \
 119                 static struct urcu_tls __tls_ ## name = {       \
 120                         .init_mutex = PTHREAD_MUTEX_INITIALIZER,\
 121                         .init_done = 0,                         \
 122                 };                                              \
 123                 __typeof__(type) *__tls_p;                      \
 124                 if (!__tls_ ## name.init_done) {                \
 125                         /* Mutex to protect concurrent init */  \
 126                         pthread_mutex_lock(&__tls_ ## name.init_mutex); \
 127                         if (!__tls_ ## name.init_done) {        \
 128                                 (void) pthread_key_create(&__tls_ ## name.key, \
 129                                         free);                  \
 130                                 cmm_smp_wmb();  /* create key before write init_done */ \
 131                                 __tls_ ## name.init_done = 1;   \
 132                         }                                       \
 133                         pthread_mutex_unlock(&__tls_ ## name.init_mutex); \
 134                 }                                               \
 135                 cmm_smp_rmb();  /* read init_done before getting key */ \
 136                 __tls_p = pthread_getspecific(__tls_ ## name.key); \
 137                 if (caa_unlikely(__tls_p == NULL)) {            \
 138                         __tls_p = calloc(1, sizeof(type));      \
 139                         do_init                                 \
 140                         (void) pthread_setspecific(__tls_ ## name.key,  \
 141                                 __tls_p);                       \
 142                 }                                               \
 143                 return __tls_p;                                 \
 144         }
 145
 146 # define _URCU_TLS_INIT(init)                                   \
 147         *__tls_p = (init);
 148
 149 # define DEFINE_URCU_TLS_INIT(type, name, init)                 \
 150         DEFINE_URCU_TLS_INIT_1(type, name, _URCU_TLS_INIT(init))
 151
 152 # define DEFINE_URCU_TLS(type, name)                            \
 153         DEFINE_URCU_TLS_INIT_1(type, name, /* empty */)
 154
 155 # define URCU_TLS_1(name)       (*__tls_access_ ## name())
 156
 157 # define URCU_TLS(name)         URCU_TLS_1(name)
 158
 159 #endif  /* #else #ifndef CONFIG_RCU_TLS */
 160
 161 #ifdef __cplusplus
 162 }
 163 #endif
 164
 165 #endif /* _URCU_TLS_COMPAT_H */