Cleanup: Re-organise source dir

[userspace-rcu.git] / include / urcu / tls-compat.h

diff --git a/include/urcu/tls-compat.h b/include/urcu/tls-compat.h
new file mode 100644 (file)
index 0000000..8ac1ea0
--- /dev/null
+++ b/include/urcu/tls-compat.h
@@ -0,0 +1,140 @@
+#ifndef _URCU_TLS_COMPAT_H
+#define _URCU_TLS_COMPAT_H
+
+/*
+ * urcu/tls-compat.h
+ *
+ * Userspace RCU library - Thread-Local Storage Compatibility Header
+ *
+ * Copyright 2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <stdlib.h>
+#include <urcu/config.h>
+#include <urcu/compiler.h>
+#include <urcu/arch.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifdef CONFIG_RCU_TLS  /* Based on ax_tls.m4 */
+
+/*
+ * Hint: How to define/declare TLS variables of compound types
+ *       such as array or function pointers?
+ *
+ * Answer: Use typedef to assign a type_name to the compound type.
+ * Example: Define a TLS variable which is an int array with len=4:
+ *
+ *     typedef int my_int_array_type[4];
+ *     DEFINE_URCU_TLS(my_int_array_type, var_name);
+ *
+ * Another example:
+ *     typedef void (*call_rcu_flavor)(struct rcu_head *, XXXX);
+ *     DECLARE_URCU_TLS(call_rcu_flavor, p_call_rcu);
+ *
+ * NOTE: URCU_TLS() is NOT async-signal-safe, you can't use it
+ * inside any function which can be called from signal handler.
+ *
+ * But if pthread_getspecific() is async-signal-safe in your
+ * platform, you can make URCU_TLS() async-signal-safe via:
+ * ensuring the first call to URCU_TLS() of a given TLS variable of
+ * all threads is called earliest from a non-signal handler function.
+ *
+ * Example: In any thread, the first call of URCU_TLS(rcu_reader)
+ * is called from rcu_register_thread(), so we can ensure all later
+ * URCU_TLS(rcu_reader) in any thread is async-signal-safe.
+ *
+ * Moreover, URCU_TLS variables should not be touched from signal
+ * handlers setup with with sigaltstack(2).
+ */
+
+# define DECLARE_URCU_TLS(type, name)  \
+       CONFIG_RCU_TLS type name
+
+# define DEFINE_URCU_TLS(type, name)   \
+       CONFIG_RCU_TLS type name
+
+# define URCU_TLS(name)                (name)
+
+#else /* #ifndef CONFIG_RCU_TLS */
+
+/*
+ * The *_1() macros ensure macro parameters are expanded.
+ */
+
+# include <pthread.h>
+
+struct urcu_tls {
+       pthread_key_t key;
+       pthread_mutex_t init_mutex;
+       int init_done;
+};
+
+# define DECLARE_URCU_TLS_1(type, name)                                \
+       type *__tls_access_ ## name(void)
+# define DECLARE_URCU_TLS(type, name)                          \
+       DECLARE_URCU_TLS_1(type, name)
+
+/*
+ * Note: we don't free memory at process exit, since it will be dealt
+ * with by the OS.
+ */
+# define DEFINE_URCU_TLS_1(type, name)                         \
+       type *__tls_access_ ## name(void)                       \
+       {                                                       \
+               static struct urcu_tls __tls_ ## name = {       \
+                       .init_mutex = PTHREAD_MUTEX_INITIALIZER,\
+                       .init_done = 0,                         \
+               };                                              \
+               void *__tls_p;                                  \
+               if (!__tls_ ## name.init_done) {                \
+                       /* Mutex to protect concurrent init */  \
+                       pthread_mutex_lock(&__tls_ ## name.init_mutex); \
+                       if (!__tls_ ## name.init_done) {        \
+                               (void) pthread_key_create(&__tls_ ## name.key, \
+                                       free);                  \
+                               cmm_smp_wmb();  /* create key before write init_done */ \
+                               __tls_ ## name.init_done = 1;   \
+                       }                                       \
+                       pthread_mutex_unlock(&__tls_ ## name.init_mutex); \
+               }                                               \
+               cmm_smp_rmb();  /* read init_done before getting key */ \
+               __tls_p = pthread_getspecific(__tls_ ## name.key); \
+               if (caa_unlikely(__tls_p == NULL)) {            \
+                       __tls_p = calloc(1, sizeof(type));      \
+                       (void) pthread_setspecific(__tls_ ## name.key,  \
+                               __tls_p);                       \
+               }                                               \
+               return __tls_p;                                 \
+       }
+
+# define DEFINE_URCU_TLS(type, name)                           \
+       DEFINE_URCU_TLS_1(type, name)
+
+# define URCU_TLS_1(name)      (*__tls_access_ ## name())
+
+# define URCU_TLS(name)                URCU_TLS_1(name)
+
+#endif /* #else #ifndef CONFIG_RCU_TLS */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _URCU_TLS_COMPAT_H */