X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=src%2Furcu-wait.h;h=c586ec9da8a007519cc7d6a793a9b6598cea46be;hp=47ac5eb35884f437ca299e48cf656e2c301557f7;hb=HEAD;hpb=cafe8ce139ea02d497582c4abb27d065e6e46d79

diff --git a/src/urcu-wait.h b/src/urcu-wait.h
index 47ac5eb..d77282b 100644
--- a/src/urcu-wait.h
+++ b/src/urcu-wait.h
@@ -1,30 +1,18 @@
+// SPDX-FileCopyrightText: 2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+//
+// SPDX-License-Identifier: LGPL-2.1-or-later
+
 #ifndef _URCU_WAIT_H
 #define _URCU_WAIT_H
 
 /*
- * urcu-wait.h
- *
  * Userspace RCU library wait/wakeup management
- *
- * Copyright (c) 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 <urcu/assert.h>
 #include <urcu/uatomic.h>
 #include <urcu/wfstack.h>
+#include <urcu/futex.h>
 #include "urcu-die.h"
 
 /*
@@ -48,7 +36,7 @@ struct urcu_wait_node {
 };
 
 #define URCU_WAIT_NODE_INIT(name, _state)		\
-	{ .state = _state }
+	{ .node = { .next = NULL }, .state = _state }
 
 #define DEFINE_URCU_WAIT_NODE(name, state)		\
 	struct urcu_wait_node name = URCU_WAIT_NODE_INIT(name, state)
@@ -125,16 +113,15 @@ void urcu_wait_node_init(struct urcu_wait_node *node,
 static inline
 void urcu_adaptative_wake_up(struct urcu_wait_node *wait)
 {
-	cmm_smp_mb();
-	assert(uatomic_read(&wait->state) == URCU_WAIT_WAITING);
-	uatomic_set(&wait->state, URCU_WAIT_WAKEUP);
+	urcu_posix_assert(uatomic_read(&wait->state) == URCU_WAIT_WAITING);
+	uatomic_store(&wait->state, URCU_WAIT_WAKEUP, CMM_RELEASE);
 	if (!(uatomic_read(&wait->state) & URCU_WAIT_RUNNING)) {
 		if (futex_noasync(&wait->state, FUTEX_WAKE, 1,
 				NULL, NULL, 0) < 0)
 			urcu_die(errno);
 	}
 	/* Allow teardown of struct urcu_wait memory. */
-	uatomic_or(&wait->state, URCU_WAIT_TEARDOWN);
+	uatomic_or_mo(&wait->state, URCU_WAIT_TEARDOWN, CMM_RELEASE);
 }
 
 /*
@@ -149,19 +136,30 @@ void urcu_adaptative_busy_wait(struct urcu_wait_node *wait)
 	/* Load and test condition before read state */
 	cmm_smp_rmb();
 	for (i = 0; i < URCU_WAIT_ATTEMPTS; i++) {
-		if (uatomic_read(&wait->state) != URCU_WAIT_WAITING)
+		if (uatomic_load(&wait->state, CMM_ACQUIRE) != URCU_WAIT_WAITING)
 			goto skip_futex_wait;
 		caa_cpu_relax();
 	}
-	while (futex_noasync(&wait->state, FUTEX_WAIT, URCU_WAIT_WAITING,
-			NULL, NULL, 0)) {
+	while (uatomic_load(&wait->state, CMM_ACQUIRE) == URCU_WAIT_WAITING) {
+		if (!futex_noasync(&wait->state, FUTEX_WAIT, URCU_WAIT_WAITING, 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
+			 * URCU_WAIT_WAITING (spurious wakeups). Check
+			 * the value again in user-space to validate
+			 * whether it really differs from
+			 * URCU_WAIT_WAITING.
+			 */
+			continue;
+		}
 		switch (errno) {
-		case EWOULDBLOCK:
+		case EAGAIN:
 			/* Value already changed. */
 			goto skip_futex_wait;
 		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);
@@ -177,13 +175,13 @@ skip_futex_wait:
 	 * memory allocated for struct urcu_wait.
 	 */
 	for (i = 0; i < URCU_WAIT_ATTEMPTS; i++) {
-		if (uatomic_read(&wait->state) & URCU_WAIT_TEARDOWN)
+		if (uatomic_load(&wait->state, CMM_RELAXED) & URCU_WAIT_TEARDOWN)
 			break;
 		caa_cpu_relax();
 	}
-	while (!(uatomic_read(&wait->state) & URCU_WAIT_TEARDOWN))
+	while (!(uatomic_load(&wait->state, CMM_ACQUIRE) & URCU_WAIT_TEARDOWN))
 		poll(NULL, 0, 10);
-	assert(uatomic_read(&wait->state) & URCU_WAIT_TEARDOWN);
+	urcu_posix_assert(uatomic_read(&wait->state) & URCU_WAIT_TEARDOWN);
 }
 
 static inline
@@ -197,7 +195,7 @@ void urcu_wake_all_waiters(struct urcu_waiters *waiters)
 			caa_container_of(iter, struct urcu_wait_node, node);
 
 		/* Don't wake already running threads */
-		if (wait_node->state & URCU_WAIT_RUNNING)
+		if (uatomic_load(&wait_node->state, CMM_RELAXED) & URCU_WAIT_RUNNING)
 			continue;
 		urcu_adaptative_wake_up(wait_node);
 	}