X-Git-Url: http://git.lttng.org/?a=blobdiff_plain;f=liblttng-ust-java-agent%2Fjava%2Flttng-ust-agent-common%2Forg%2Flttng%2Fust%2Fagent%2Fcontext%2FContextInfoManager.java;h=22efe022e794c3b1930570f560df5b408567ea2a;hb=c0c0989ab70574e09b2f7e8b48c2da6af664a849;hp=86ded59b346ab6984ca4594826d4d9f5716cb5d4;hpb=cad6b749231be8c91fcfd3616934032b5dfd3614;p=lttng-ust.git

diff --git a/liblttng-ust-java-agent/java/lttng-ust-agent-common/org/lttng/ust/agent/context/ContextInfoManager.java b/liblttng-ust-java-agent/java/lttng-ust-agent-common/org/lttng/ust/agent/context/ContextInfoManager.java
index 86ded59b..22efe022 100644
--- a/liblttng-ust-java-agent/java/lttng-ust-agent-common/org/lttng/ust/agent/context/ContextInfoManager.java
+++ b/liblttng-ust-java-agent/java/lttng-ust-agent-common/org/lttng/ust/agent/context/ContextInfoManager.java
@@ -1,18 +1,8 @@
 /*
- * Copyright (C) 2015 - EfficiOS Inc., Alexandre Montplaisir <alexmonthy@efficios.com>
+ * SPDX-License-Identifier: LGPL-2.1-only
  *
- * This library is free software; you can redistribute it and/or modify it
- * under the terms of the GNU Lesser General Public License, version 2.1 only,
- * as published by the Free Software Foundation.
- *
- * 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
+ * Copyright (C) 2015 EfficiOS Inc.
+ * Copyright (C) 2015 Alexandre Montplaisir <alexmonthy@efficios.com>
  */
 
 package org.lttng.ust.agent.context;
@@ -40,6 +30,10 @@ public final class ContextInfoManager {
 	private final Map<String, IContextInfoRetriever> contextInfoRetrievers = new ConcurrentHashMap<String, IContextInfoRetriever>();
 	private final Map<String, Long> contextInforRetrieverRefs = new HashMap<String, Long>();
 
+	/**
+	 * Lock used to keep the two maps above in sync when retrievers are
+	 * registered or unregistered.
+	 */
 	private final Object retrieverLock = new Object();
 
 	/** Singleton class, constructor should not be accessed directly */
@@ -163,6 +157,13 @@ public final class ContextInfoManager {
 	 *         was none
 	 */
 	public IContextInfoRetriever getContextInfoRetriever(String retrieverName) {
+		/*
+		 * Note that this method does not take the retrieverLock, it lets
+		 * concurrent threads access the ConcurrentHashMap directly.
+		 *
+		 * It's fine for a get() to happen during a registration or
+		 * unregistration, it's first-come-first-serve.
+		 */
 		return contextInfoRetrievers.get(retrieverName);
 	}