*
* Userspace RCU library
*
- * Copyright February 2009 - Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
+ * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
+ * Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
*
- * Distributed under LGPLv2.1
+ * 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
*
* IBM's contributions to this file may be relicensed under LGPLv2 or later.
*/
/* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
#include "urcu.h"
+#ifndef DEBUG_FULL_MB
+void __attribute__((constructor)) urcu_init(void);
+void __attribute__((destructor)) urcu_exit(void);
+#else
+static inline void urcu_init(void)
+{
+}
+#endif
+
+int init_done;
+
pthread_mutex_t urcu_mutex = PTHREAD_MUTEX_INITIALIZER;
/*
* Ensured by STORE_SHARED and LOAD_SHARED.
*/
+ /*
+ * Adding a smp_mb() which is _not_ formally required, but makes the
+ * model easier to understand. It does not have a big performance impact
+ * anyway, given this is the write-side.
+ */
+ smp_mb();
+
/*
* Wait for previous parity to be empty of readers.
*/
* Ensured by STORE_SHARED and LOAD_SHARED.
*/
+ /*
+ * Adding a smp_mb() which is _not_ formally required, but makes the
+ * model easier to understand. It does not have a big performance impact
+ * anyway, given this is the write-side.
+ */
+ smp_mb();
+
switch_next_urcu_qparity(); /* 1 -> 0 */
/*
* Ensured by STORE_SHARED and LOAD_SHARED.
*/
+ /*
+ * Adding a smp_mb() which is _not_ formally required, but makes the
+ * model easier to understand. It does not have a big performance impact
+ * anyway, given this is the write-side.
+ */
+ smp_mb();
+
/*
* Wait for previous parity to be empty of readers.
*/
void rcu_register_thread(void)
{
internal_urcu_lock();
+ urcu_init(); /* In case gcc does not support constructor attribute */
rcu_add_reader(pthread_self());
internal_urcu_unlock();
}
smp_mb();
}
-void __attribute__((constructor)) urcu_init(void)
+/*
+ * urcu_init constructor. Called when the library is linked, but also when
+ * reader threads are calling rcu_register_thread().
+ * Should only be called by a single thread at a given time. This is ensured by
+ * holing the internal_urcu_lock() from rcu_register_thread() or by running at
+ * library load time, which should not be executed by multiple threads nor
+ * concurrently with rcu_register_thread() anyway.
+ */
+void urcu_init(void)
{
struct sigaction act;
int ret;
+ if (init_done)
+ return;
+ init_done = 1;
+
act.sa_sigaction = sigurcu_handler;
+ act.sa_flags = SA_SIGINFO;
+ sigemptyset(&act.sa_mask);
ret = sigaction(SIGURCU, &act, NULL);
if (ret) {
perror("Error in sigaction");
}
}
-void __attribute__((destructor)) urcu_exit(void)
+void urcu_exit(void)
{
struct sigaction act;
int ret;