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   /* Based on ax_tls.m4 */
  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 exmaple:
  48  *      typedef void (*call_rcu_flavor)(struct rcu_head *, XXXX);
  49  *      DECLARE_URCU_TLS(call_rcu_flavor, p_call_rcu);
  50  */
  51
  52 # define DECLARE_URCU_TLS(type, name)   \
  53         CONFIG_RCU_TLS type name
  54
  55 # define DEFINE_URCU_TLS(type, name)    \
  56         CONFIG_RCU_TLS type name
  57
  58 # define URCU_TLS(name)         (name)
  59
  60 #else /* #ifndef CONFIG_RCU_TLS */
  61
  62 # include <pthread.h>
  63
  64 struct urcu_tls {
  65         pthread_key_t key;
  66         pthread_mutex_t init_mutex;
  67         int init_done;
  68 };
  69
  70 # define DECLARE_URCU_TLS(type, name)                           \
  71         type *__tls_access_ ## name(void)
  72
  73 /*
  74  * Note: we don't free memory at process exit, since it will be dealt
  75  * with by the OS.
  76  */
  77 # define DEFINE_URCU_TLS(type, name)                            \
  78         type *__tls_access_ ## name(void)                       \
  79         {                                                       \
  80                 static struct urcu_tls __tls_ ## name = {       \
  81                         .init_mutex = PTHREAD_MUTEX_INITIALIZER,\
  82                         .init_done = 0,                         \
  83                 };                                              \
  84                 void *__tls_p;                                  \
  85                 if (!__tls_ ## name.init_done) {                \
  86                         /* Mutex to protect concurrent init */  \
  87                         pthread_mutex_lock(&__tls_ ## name.init_mutex); \
  88                         if (!__tls_ ## name.init_done) {        \
  89                                 (void) pthread_key_create(&__tls_ ## name.key, \
  90                                         free);                  \
  91                                 cmm_smp_wmb();  /* create key before write init_done */ \
  92                                 __tls_ ## name.init_done = 1;   \
  93                         }                                       \
  94                         pthread_mutex_unlock(&__tls_ ## name.init_mutex); \
  95                 }                                               \
  96                 cmm_smp_rmb();  /* read init_done before getting key */ \
  97                 __tls_p = pthread_getspecific(__tls_ ## name.key); \
  98                 if (caa_unlikely(__tls_p == NULL)) {            \
  99                         __tls_p = calloc(1, sizeof(type));      \
 100                         (void) pthread_setspecific(__tls_ ## name.key,  \
 101                                 __tls_p);                       \
 102                 }                                               \
 103                 return __tls_p;                                 \
 104         }
 105
 106 # define URCU_TLS(name)         (*__tls_access_ ## name())
 107
 108 #endif  /* #else #ifndef CONFIG_RCU_TLS */
 109
 110 #ifdef __cplusplus
 111 }
 112 #endif
 113
 114 #endif /* _URCU_TLS_COMPAT_H */