X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=src%2Furcu-qsbr.c;h=98e27655031ac1afe8985ae5b9089d5d968dfb7c;hb=acdb82a20ba20467b89c67aa44ca03da610513a9;hp=40c0fbdb35519983186c67615f8c285a691f91d8;hpb=a0ec6d9b6b67e37fc81c98e04008907bc500cde8;p=userspace-rcu.git

diff --git a/src/urcu-qsbr.c b/src/urcu-qsbr.c
index 40c0fbd..98e2765 100644
--- a/src/urcu-qsbr.c
+++ b/src/urcu-qsbr.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-qsbr.c
- *
  * Userspace RCU QSBR 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.
  */
 
@@ -28,13 +14,13 @@
 #include <stdio.h>
 #include <pthread.h>
 #include <signal.h>
-#include <assert.h>
 #include <stdlib.h>
 #include <stdint.h>
 #include <string.h>
 #include <errno.h>
 #include <poll.h>
 
+#include <urcu/assert.h>
 #include <urcu/wfcqueue.h>
 #include <urcu/map/urcu-qsbr.h>
 #define BUILD_QSBR_LIB
@@ -53,6 +39,7 @@
 #define _LGPL_SOURCE
 
 void __attribute__((destructor)) urcu_qsbr_exit(void);
+static void urcu_call_rcu_exit(void);
 
 /*
  * rcu_gp_lock ensures mutual exclusion between threads calling
@@ -123,17 +110,25 @@ static void wait_gp(void)
 {
 	/* Read reader_gp before read futex */
 	cmm_smp_rmb();
-	if (uatomic_read(&urcu_qsbr_gp.futex) != -1)
-		return;
-	while (futex_noasync(&urcu_qsbr_gp.futex, FUTEX_WAIT, -1,
-			NULL, NULL, 0)) {
+	while (uatomic_read(&urcu_qsbr_gp.futex) == -1) {
+		if (!futex_noasync(&urcu_qsbr_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. */
 			return;
 		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);
@@ -278,7 +273,7 @@ void urcu_qsbr_synchronize_rcu(void)
 	/*
 	 * Wait for readers to observe original parity or be quiescent.
 	 * wait_for_readers() can release and grab again rcu_registry_lock
-	 * interally.
+	 * internally.
 	 */
 	wait_for_readers(&registry, &cur_snap_readers, &qsreaders);
 
@@ -321,7 +316,7 @@ void urcu_qsbr_synchronize_rcu(void)
 	/*
 	 * Wait for readers to observe new parity or be quiescent.
 	 * wait_for_readers() can release and grab again rcu_registry_lock
-	 * interally.
+	 * internally.
 	 */
 	wait_for_readers(&cur_snap_readers, NULL, &qsreaders);
 
@@ -410,7 +405,7 @@ void urcu_qsbr_synchronize_rcu(void)
 	/*
 	 * Wait for readers to observe new count of be quiescent.
 	 * wait_for_readers() can release and grab again rcu_registry_lock
-	 * interally.
+	 * internally.
 	 */
 	wait_for_readers(&registry, NULL, &qsreaders);
 
@@ -470,10 +465,10 @@ void urcu_qsbr_thread_online(void)
 void urcu_qsbr_register_thread(void)
 {
 	URCU_TLS(urcu_qsbr_reader).tid = pthread_self();
-	assert(URCU_TLS(urcu_qsbr_reader).ctr == 0);
+	urcu_posix_assert(URCU_TLS(urcu_qsbr_reader).ctr == 0);
 
 	mutex_lock(&rcu_registry_lock);
-	assert(!URCU_TLS(urcu_qsbr_reader).registered);
+	urcu_posix_assert(!URCU_TLS(urcu_qsbr_reader).registered);
 	URCU_TLS(urcu_qsbr_reader).registered = 1;
 	cds_list_add(&URCU_TLS(urcu_qsbr_reader).node, &registry);
 	mutex_unlock(&rcu_registry_lock);
@@ -487,7 +482,7 @@ void urcu_qsbr_unregister_thread(void)
 	 * with a waiting writer.
 	 */
 	_urcu_qsbr_thread_offline();
-	assert(URCU_TLS(urcu_qsbr_reader).registered);
+	urcu_posix_assert(URCU_TLS(urcu_qsbr_reader).registered);
 	URCU_TLS(urcu_qsbr_reader).registered = 0;
 	mutex_lock(&rcu_registry_lock);
 	cds_list_del(&URCU_TLS(urcu_qsbr_reader).node);
@@ -499,11 +494,13 @@ void urcu_qsbr_exit(void)
 	/*
 	 * Assertion disabled because call_rcu threads are now rcu
 	 * readers, and left running at exit.
-	 * assert(cds_list_empty(&registry));
+	 * urcu_posix_assert(cds_list_empty(&registry));
 	 */
+	urcu_call_rcu_exit();
 }
 
 DEFINE_RCU_FLAVOR(rcu_flavor);
 
 #include "urcu-call-rcu-impl.h"
 #include "urcu-defer-impl.h"
+#include "urcu-poll-impl.h"