Add CMM memory model

[userspace-rcu.git] / src / urcu.c

diff --git a/src/urcu.c b/src/urcu.c
index 67c6525ddc9479cd0c63de0805998c99fa32b07c..ccc134ca9d8c79363523c9b2b9670cd919ab5784 100644 (file)
--- a/src/urcu.c
+++ b/src/urcu.c
@@ -1,25 +1,11 @@
+// SPDX-FileCopyrightText: 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+// SPDX-FileCopyrightText: 2009 Paul E. McKenney, IBM Corporation.
+//
+// SPDX-License-Identifier: LGPL-2.1-or-later
+
 /*
- * urcu.c
- *
  * Userspace RCU library
  *
- * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- * Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
- *
- * 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.
  */
 
@@ -109,9 +95,13 @@ void rcu_init(void)
 static int init_done;
 
 void __attribute__((constructor)) rcu_init(void);
-void __attribute__((destructor)) rcu_exit(void);
+
+static DEFINE_URCU_TLS(int, rcu_signal_was_blocked);
 #endif
 
+void __attribute__((destructor)) rcu_exit(void);
+static void urcu_call_rcu_exit(void);
+
 /*
  * rcu_gp_lock ensures mutual exclusion between threads calling
  * synchronize_rcu().
@@ -259,17 +249,25 @@ static void wait_gp(void)
        smp_mb_master();
        /* Temporarily unlock the registry lock. */
        mutex_unlock(&rcu_registry_lock);
-       if (uatomic_read(&rcu_gp.futex) != -1)
-               goto end;
-       while (futex_async(&rcu_gp.futex, FUTEX_WAIT, -1,
-                       NULL, NULL, 0)) {
+       while (uatomic_read(&rcu_gp.futex) == -1) {
+               if (!futex_async(&rcu_gp.futex, FUTEX_WAIT, -1, NULL, NULL, 0)) {
+                       /*
+                        * Prior queued wakeups queued by unrelated code
+                        * using the same address can cause futex wait to
+                        * return 0 even through the futex value is still
+                        * -1 (spurious wakeups). Check the value again
+                        * in user-space to validate whether it really
+                        * differs from -1.
+                        */
+                       continue;
+               }
                switch (errno) {
-               case EWOULDBLOCK:
+               case EAGAIN:
                        /* Value already changed. */
                        goto end;
                case EINTR:
                        /* Retry if interrupted by signal. */
-                       break;  /* Get out of switch. */
+                       break;  /* Get out of switch. Check again. */
                default:
                        /* Unexpected error. */
                        urcu_die(errno);
@@ -529,8 +527,52 @@ int rcu_read_ongoing(void)
        return _rcu_read_ongoing();
 }
 
+#ifdef RCU_SIGNAL
+/*
+ * Make sure the signal used by the urcu-signal flavor is unblocked
+ * while the thread is registered.
+ */
+static
+void urcu_signal_unblock(void)
+{
+       sigset_t mask, oldmask;
+       int ret;
+
+       ret = sigemptyset(&mask);
+       urcu_posix_assert(!ret);
+       ret = sigaddset(&mask, SIGRCU);
+       urcu_posix_assert(!ret);
+       ret = pthread_sigmask(SIG_UNBLOCK, &mask, &oldmask);
+       urcu_posix_assert(!ret);
+       URCU_TLS(rcu_signal_was_blocked) = sigismember(&oldmask, SIGRCU);
+}
+
+static
+void urcu_signal_restore(void)
+{
+       sigset_t mask;
+       int ret;
+
+       if (!URCU_TLS(rcu_signal_was_blocked))
+               return;
+       ret = sigemptyset(&mask);
+       urcu_posix_assert(!ret);
+       ret = sigaddset(&mask, SIGRCU);
+       urcu_posix_assert(!ret);
+       ret = pthread_sigmask(SIG_BLOCK, &mask, NULL);
+       urcu_posix_assert(!ret);
+}
+#else
+static
+void urcu_signal_unblock(void) { }
+static
+void urcu_signal_restore(void) { }
+#endif
+
 void rcu_register_thread(void)
 {
+       urcu_signal_unblock();
+
        URCU_TLS(rcu_reader).tid = pthread_self();
        urcu_posix_assert(URCU_TLS(rcu_reader).need_mb == 0);
        urcu_posix_assert(!(URCU_TLS(rcu_reader).ctr & URCU_GP_CTR_NEST_MASK));
@@ -550,6 +592,8 @@ void rcu_unregister_thread(void)
        URCU_TLS(rcu_reader).registered = 0;
        cds_list_del(&URCU_TLS(rcu_reader).node);
        mutex_unlock(&rcu_registry_lock);
+
+       urcu_signal_restore();
 }
 
 #ifdef RCU_MEMBARRIER
@@ -640,21 +684,24 @@ void rcu_init(void)
                urcu_die(errno);
 }
 
+/*
+ * Don't unregister the SIGRCU signal handler anymore, because
+ * call_rcu threads could still be using it shortly before the
+ * application exits.
+ * Assertion disabled because call_rcu threads are now rcu
+ * readers, and left running at exit.
+ * urcu_posix_assert(cds_list_empty(&registry));
+ */
+
+#endif /* #ifdef RCU_SIGNAL */
+
 void rcu_exit(void)
 {
-       /*
-        * Don't unregister the SIGRCU signal handler anymore, because
-        * call_rcu threads could still be using it shortly before the
-        * application exits.
-        * Assertion disabled because call_rcu threads are now rcu
-        * readers, and left running at exit.
-        * urcu_posix_assert(cds_list_empty(&registry));
-        */
+       urcu_call_rcu_exit();
 }
 
-#endif /* #ifdef RCU_SIGNAL */
-
 DEFINE_RCU_FLAVOR(rcu_flavor);
 
 #include "urcu-call-rcu-impl.h"
 #include "urcu-defer-impl.h"
+#include "urcu-poll-impl.h"