urcu.c: declare noop urcu_init() function non-static

[urcu.git] / urcu.c

diff --git a/urcu.c b/urcu.c
index 7ab87c4e4f00fb61ef3a8931494754d7bfcf0188..c210a1341ade8a189752417249bb47bca73a03aa 100644 (file)
--- a/urcu.c
+++ b/urcu.c
@@ -3,9 +3,22 @@
  *
  * 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.
  */
@@ -23,6 +36,17 @@
 /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
 #include "urcu.h"
 
+#ifndef CONFIG_URCU_AVOID_SIGNALS
+void __attribute__((constructor)) urcu_init(void);
+void __attribute__((destructor)) urcu_exit(void);
+#else
+void urcu_init(void)
+{
+}
+#endif
+
+int init_done;
+
 pthread_mutex_t urcu_mutex = PTHREAD_MUTEX_INITIALIZER;
 
 /*
@@ -103,7 +127,7 @@ static void switch_next_urcu_qparity(void)
        STORE_SHARED(urcu_gp_ctr, urcu_gp_ctr ^ RCU_GP_CTR_BIT);
 }
 
-#ifdef DEBUG_FULL_MB
+#ifdef CONFIG_URCU_AVOID_SIGNALS
 #ifdef HAS_INCOHERENT_CACHES
 static void force_mb_single_thread(struct reader_registry *index)
 {
@@ -115,7 +139,7 @@ static void force_mb_all_threads(void)
 {
        smp_mb();
 }
-#else /* #ifdef DEBUG_FULL_MB */
+#else /* #ifdef CONFIG_URCU_AVOID_SIGNALS */
 #ifdef HAS_INCOHERENT_CACHES
 static void force_mb_single_thread(struct reader_registry *index)
 {
@@ -182,7 +206,7 @@ static void force_mb_all_threads(void)
        }
        smp_mb();       /* read ->need_mb before ending the barrier */
 }
-#endif /* #else #ifdef DEBUG_FULL_MB */
+#endif /* #else #ifdef CONFIG_URCU_AVOID_SIGNALS */
 
 void wait_for_quiescent_state(void)
 {
@@ -235,6 +259,13 @@ void synchronize_rcu(void)
         * 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.
         */
@@ -248,6 +279,13 @@ void synchronize_rcu(void)
         * 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 */
 
        /*
@@ -258,6 +296,13 @@ void synchronize_rcu(void)
         * 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.
         */
@@ -363,6 +408,7 @@ static void rcu_remove_reader(pthread_t id)
 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();
 }
@@ -374,7 +420,7 @@ void rcu_unregister_thread(void)
        internal_urcu_unlock();
 }
 
-#ifndef DEBUG_FULL_MB
+#ifndef CONFIG_URCU_AVOID_SIGNALS
 static void sigurcu_handler(int signo, siginfo_t *siginfo, void *context)
 {
        /*
@@ -387,12 +433,26 @@ static void sigurcu_handler(int signo, siginfo_t *siginfo, void *context)
        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 | SA_RESTART;
+       sigemptyset(&act.sa_mask);
        ret = sigaction(SIGURCU, &act, NULL);
        if (ret) {
                perror("Error in sigaction");
@@ -400,7 +460,7 @@ void __attribute__((constructor)) urcu_init(void)
        }
 }
 
-void __attribute__((destructor)) urcu_exit(void)
+void urcu_exit(void)
 {
        struct sigaction act;
        int ret;
@@ -413,4 +473,4 @@ void __attribute__((destructor)) urcu_exit(void)
        assert(act.sa_sigaction == sigurcu_handler);
        free(registry);
 }
-#endif /* #ifndef DEBUG_FULL_MB */
+#endif /* #ifndef CONFIG_URCU_AVOID_SIGNALS */