From 3dd47a3b94cdbeb0ef349c8212e7eb1d3d696140 Mon Sep 17 00:00:00 2001
From: Charles Honton <chonton@proofpoint.com>
Date: Wed, 21 Aug 2024 14:27:02 -0700
Subject: [PATCH 1/5] update AvoidSynchronizedAtMethodLevel message to mention
 ReentrantLock see https://openjdk.org/jeps/8337395

---
 .../category/java/multithreading.xml          | 68 +++++++++++++++++--
 1 file changed, 61 insertions(+), 7 deletions(-)

diff --git a/pmd-java/src/main/resources/category/java/multithreading.xml b/pmd-java/src/main/resources/category/java/multithreading.xml
index 88750e9ab0..89dde428b3 100644
--- a/pmd-java/src/main/resources/category/java/multithreading.xml
+++ b/pmd-java/src/main/resources/category/java/multithreading.xml
@@ -12,13 +12,13 @@ Rules that flag issues when dealing with multiple threads of execution.
     <rule name="AvoidSynchronizedAtMethodLevel"
           language="java"
           since="3.0"
-          message="Use block level rather than method level synchronization"
+          message="Use block level locking rather than method level synchronization"
           class="net.sourceforge.pmd.lang.rule.xpath.XPathRule"
           externalInfoUrl="${pmd.website.baseurl}/pmd_rules_java_multithreading.html#avoidsynchronizedatmethodlevel">
         <description>
-Method-level synchronization can cause problems when new code is added to the method.
-Block-level synchronization helps to ensure that only the code that needs synchronization
-gets it.
+Method-level synchronization will pin virtual threads and can cause performance problems. Additionally, it can cause
+problems when new code is added to the method.  Block-level ReentrantLock helps to ensure that only the code that
+needs mutual exclusion will be locked.
         </description>
         <priority>3</priority>
         <properties>
@@ -30,7 +30,7 @@ gets it.
 <![CDATA[
 public class Foo {
     // Try to avoid this:
-    synchronized void foo() {
+    synchronized void bar() {
         // code, that doesn't need synchronization
         // ...
         // code, that requires synchronization
@@ -41,13 +41,18 @@ public class Foo {
         // ...
     }
     // Prefer this:
+    Lock instanceLock = new ReentrantLock();
+
     void bar() {
         // code, that doesn't need synchronization
         // ...
-        synchronized(this) {
+        try {
+            instanceLock.lock();  // or instanceLock.tryLock(long time, TimeUnit unit)
             if (!sharedData.has("bar")) {
                 sharedData.add("bar");
             }
+        } finally {
+            instanceLock.unlock();
         }
         // more code, that doesn't need synchronization
         // ...
@@ -58,11 +63,16 @@ public class Foo {
     }
 
     // Prefer this:
+    private static Lock CLS_LOCK = new ReentrantLock();
+
     static void barStatic() {
         // code, that doesn't need synchronization
         // ...
-        synchronized(Foo.class) {
+        try {
+            CLS_LOCK.lock();
             // code, that requires synchronization
+        } finally {
+            CLS_LOCK.unlock();
         }
         // more code, that doesn't need synchronization
         // ...
@@ -72,6 +82,50 @@ public class Foo {
         </example>
     </rule>
 
+  <rule name="AvoidSynchronizedStatement"
+        language="java"
+        since="7.5.0"
+        message="Use ReentrantLock rather than synchronization"
+        class="net.sourceforge.pmd.lang.rule.xpath.XPathRule"
+        externalInfoUrl="${pmd.website.baseurl}/pmd_rules_java_multithreading.html#avoidsynchronizedstatement">
+    <description>
+      Synchronization will pin virtual threads and can cause performance problems.
+    </description>
+    <priority>3</priority>
+    <properties>
+      <property name="xpath">
+        <value>//SynchronizedStatement</value>
+      </property>
+    </properties>
+    <example>
+      <![CDATA[
+public class Foo {
+    // Try to avoid this:
+    void foo() {
+        // code that doesn't need mutual exclusion
+        synchronized(this) {
+            // code that requires mutual exclusion
+        }
+        // more code that doesn't need mutual exclusion
+    }
+    // Prefer this:
+    Lock instanceLock = new ReentrantLock();
+
+    void foo() {
+        // code that doesn't need mutual exclusion
+        try {
+            instanceLock.lock();  // or instanceLock.tryLock(long time, TimeUnit unit)
+            // code that requires mutual exclusion
+        } finally {
+            instanceLock.unlock();
+        }
+        // more code that doesn't need mutual exclusion
+    }
+}
+]]>
+    </example>
+  </rule>
+
     <rule name="AvoidThreadGroup"
           language="java"
           since="3.6"

From 8a39917fa24b5cf0a1cb398fda359ce9e2e0ad15 Mon Sep 17 00:00:00 2001
From: Charles Honton <chonton@proofpoint.com>
Date: Thu, 22 Aug 2024 13:54:17 -0700
Subject: [PATCH 2/5] added unit test

---
 .../AvoidSynchronizedStatementTest.java       | 11 +++++++
 .../xml/AvoidSynchronizedStatement.xml        | 32 +++++++++++++++++++
 2 files changed, 43 insertions(+)
 create mode 100644 pmd-java/src/test/java/net/sourceforge/pmd/lang/java/rule/multithreading/AvoidSynchronizedStatementTest.java
 create mode 100644 pmd-java/src/test/resources/net/sourceforge/pmd/lang/java/rule/multithreading/xml/AvoidSynchronizedStatement.xml

diff --git a/pmd-java/src/test/java/net/sourceforge/pmd/lang/java/rule/multithreading/AvoidSynchronizedStatementTest.java b/pmd-java/src/test/java/net/sourceforge/pmd/lang/java/rule/multithreading/AvoidSynchronizedStatementTest.java
new file mode 100644
index 0000000000..bb02194212
--- /dev/null
+++ b/pmd-java/src/test/java/net/sourceforge/pmd/lang/java/rule/multithreading/AvoidSynchronizedStatementTest.java
@@ -0,0 +1,11 @@
+/**
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
+package net.sourceforge.pmd.lang.java.rule.multithreading;
+
+import net.sourceforge.pmd.test.PmdRuleTst;
+
+class AvoidSynchronizedStatementTest extends PmdRuleTst {
+    // no additional unit tests
+}
diff --git a/pmd-java/src/test/resources/net/sourceforge/pmd/lang/java/rule/multithreading/xml/AvoidSynchronizedStatement.xml b/pmd-java/src/test/resources/net/sourceforge/pmd/lang/java/rule/multithreading/xml/AvoidSynchronizedStatement.xml
new file mode 100644
index 0000000000..811db288e9
--- /dev/null
+++ b/pmd-java/src/test/resources/net/sourceforge/pmd/lang/java/rule/multithreading/xml/AvoidSynchronizedStatement.xml
@@ -0,0 +1,32 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<test-data
+    xmlns="http://pmd.sourceforge.net/rule-tests"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://pmd.sourceforge.net/rule-tests http://pmd.sourceforge.net/rule-tests_1_0_0.xsd">
+
+    <test-code>
+        <description>TEST1</description>
+        <expected-problems>1</expected-problems>
+        <code><![CDATA[
+public class Foo {
+    void foo () {
+        synchronized(mutex) {}
+    }
+}
+        ]]></code>
+    </test-code>
+
+    <test-code>
+        <description>#991 AvoidSynchronizedStatement for static methods</description>
+        <expected-problems>1</expected-problems>
+        <code><![CDATA[
+public class Test {
+    public static void foo() {
+        synchronized(Test.class) {
+            // only a block is synchronized on Test.class
+        }
+    }
+}
+        ]]></code>
+    </test-code>
+</test-data>

From 93db59bea51292d6c9042301ba28b774aefbaf6b Mon Sep 17 00:00:00 2001
From: Andreas Dangel <andreas.dangel@adangel.org>
Date: Thu, 29 Aug 2024 12:41:02 +0200
Subject: [PATCH 3/5] Apply suggestions from code review

---
 .../resources/category/java/multithreading.xml    |  4 ++--
 .../xml/AvoidSynchronizedStatement.xml            | 15 +++++++++++++--
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/pmd-java/src/main/resources/category/java/multithreading.xml b/pmd-java/src/main/resources/category/java/multithreading.xml
index 89dde428b3..605829ce67 100644
--- a/pmd-java/src/main/resources/category/java/multithreading.xml
+++ b/pmd-java/src/main/resources/category/java/multithreading.xml
@@ -30,7 +30,7 @@ needs mutual exclusion will be locked.
 <![CDATA[
 public class Foo {
     // Try to avoid this:
-    synchronized void bar() {
+    synchronized void foo() {
         // code, that doesn't need synchronization
         // ...
         // code, that requires synchronization
@@ -63,7 +63,7 @@ public class Foo {
     }
 
     // Prefer this:
-    private static Lock CLS_LOCK = new ReentrantLock();
+    private static Lock CLASS_LOCK = new ReentrantLock();
 
     static void barStatic() {
         // code, that doesn't need synchronization
diff --git a/pmd-java/src/test/resources/net/sourceforge/pmd/lang/java/rule/multithreading/xml/AvoidSynchronizedStatement.xml b/pmd-java/src/test/resources/net/sourceforge/pmd/lang/java/rule/multithreading/xml/AvoidSynchronizedStatement.xml
index 811db288e9..d5962a3c11 100644
--- a/pmd-java/src/test/resources/net/sourceforge/pmd/lang/java/rule/multithreading/xml/AvoidSynchronizedStatement.xml
+++ b/pmd-java/src/test/resources/net/sourceforge/pmd/lang/java/rule/multithreading/xml/AvoidSynchronizedStatement.xml
@@ -5,7 +5,7 @@
     xsi:schemaLocation="http://pmd.sourceforge.net/rule-tests http://pmd.sourceforge.net/rule-tests_1_0_0.xsd">
 
     <test-code>
-        <description>TEST1</description>
+        <description>Synchronized block in instance method</description>
         <expected-problems>1</expected-problems>
         <code><![CDATA[
 public class Foo {
@@ -17,7 +17,7 @@ public class Foo {
     </test-code>
 
     <test-code>
-        <description>#991 AvoidSynchronizedStatement for static methods</description>
+        <description>Synchronized block in static methods</description>
         <expected-problems>1</expected-problems>
         <code><![CDATA[
 public class Test {
@@ -26,6 +26,17 @@ public class Test {
             // only a block is synchronized on Test.class
         }
     }
+}
+        ]]></code>
+    </test-code>
+    
+    <test-code>
+        <description>synchronized methods are not flagged - we have a separate rule AvoidSynchronizedAtMethodLevel for that</description>
+        <expected-problems>0</expected-problems>
+        <code><![CDATA[
+public class Test {
+    public synchronized void foo() {}
+    public static synchronized void fooStatic() {}
 }
         ]]></code>
     </test-code>

From a4cac6b74f26c952f7cdfc973a000feaa3b4f98e Mon Sep 17 00:00:00 2001
From: Andreas Dangel <andreas.dangel@pmd-code.org>
Date: Thu, 29 Aug 2024 12:46:30 +0200
Subject: [PATCH 4/5]  Update @chonton as a contributor

---
 .all-contributorsrc                   | 3 ++-
 docs/pages/pmd/projectdocs/credits.md | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/.all-contributorsrc b/.all-contributorsrc
index f76cd95f82..bc334b0795 100644
--- a/.all-contributorsrc
+++ b/.all-contributorsrc
@@ -1929,7 +1929,8 @@
       "avatar_url": "https://avatars.githubusercontent.com/u/1444125?v=4",
       "profile": "http://www.linkedin.com/in/chonton",
       "contributions": [
-        "bug"
+        "bug",
+        "code"
       ]
     },
     {
diff --git a/docs/pages/pmd/projectdocs/credits.md b/docs/pages/pmd/projectdocs/credits.md
index 7cbe0baec8..f292c30e7e 100644
--- a/docs/pages/pmd/projectdocs/credits.md
+++ b/docs/pages/pmd/projectdocs/credits.md
@@ -171,7 +171,7 @@ Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/d
       <td align="center" valign="top" width="14.28%"><a href="https://c-otto.de/"><img src="https://avatars.githubusercontent.com/u/344948?v=4?s=100" width="100px;" alt="Carsten Otto"/><br /><sub><b>Carsten Otto</b></sub></a><br /><a href="https://github.com/pmd/pmd/issues?q=author%3AC-Otto" title="Bug reports">🐛</a></td>
       <td align="center" valign="top" width="14.28%"><a href="https://github.com/HoushCE29"><img src="https://avatars.githubusercontent.com/u/22387324?v=4?s=100" width="100px;" alt="Charlie Housh"/><br /><sub><b>Charlie Housh</b></sub></a><br /><a href="https://github.com/pmd/pmd/issues?q=author%3AHoushCE29" title="Bug reports">🐛</a></td>
       <td align="center" valign="top" width="14.28%"><a href="https://github.com/ChuckJonas"><img src="https://avatars.githubusercontent.com/u/5217568?v=4?s=100" width="100px;" alt="Charlie Jonas"/><br /><sub><b>Charlie Jonas</b></sub></a><br /><a href="https://github.com/pmd/pmd/issues?q=author%3AChuckJonas" title="Bug reports">🐛</a></td>
-      <td align="center" valign="top" width="14.28%"><a href="http://www.linkedin.com/in/chonton"><img src="https://avatars.githubusercontent.com/u/1444125?v=4?s=100" width="100px;" alt="Chas Honton"/><br /><sub><b>Chas Honton</b></sub></a><br /><a href="https://github.com/pmd/pmd/issues?q=author%3Achonton" title="Bug reports">🐛</a></td>
+      <td align="center" valign="top" width="14.28%"><a href="http://www.linkedin.com/in/chonton"><img src="https://avatars.githubusercontent.com/u/1444125?v=4?s=100" width="100px;" alt="Chas Honton"/><br /><sub><b>Chas Honton</b></sub></a><br /><a href="https://github.com/pmd/pmd/issues?q=author%3Achonton" title="Bug reports">🐛</a> <a href="https://github.com/pmd/pmd/commits?author=chonton" title="Code">💻</a></td>
       <td align="center" valign="top" width="14.28%"><a href="https://github.com/willamette"><img src="https://avatars.githubusercontent.com/u/1435016?v=4?s=100" width="100px;" alt="Chen Yang"/><br /><sub><b>Chen Yang</b></sub></a><br /><a href="https://github.com/pmd/pmd/issues?q=author%3Awillamette" title="Bug reports">🐛</a></td>
       <td align="center" valign="top" width="14.28%"><a href="https://github.com/bashagithub"><img src="https://avatars.githubusercontent.com/u/25314601?v=4?s=100" width="100px;" alt="Chotu"/><br /><sub><b>Chotu</b></sub></a><br /><a href="https://github.com/pmd/pmd/issues?q=author%3Abashagithub" title="Bug reports">🐛</a></td>
       <td align="center" valign="top" width="14.28%"><a href="https://github.com/tophersmith"><img src="https://avatars.githubusercontent.com/u/812876?v=4?s=100" width="100px;" alt="Chris Smith"/><br /><sub><b>Chris Smith</b></sub></a><br /><a href="https://github.com/pmd/pmd/issues?q=author%3Atophersmith" title="Bug reports">🐛</a></td>

From 3c3be3c81dd3fdf0d759c26276fbaebf985ca1cf Mon Sep 17 00:00:00 2001
From: Andreas Dangel <andreas.dangel@pmd-code.org>
Date: Thu, 29 Aug 2024 12:48:14 +0200
Subject: [PATCH 5/5] [doc] Update release notes (#5175)

---
 docs/pages/release_notes.md                              | 8 ++++++++
 pmd-java/src/main/resources/rulesets/java/quickstart.xml | 1 +
 2 files changed, 9 insertions(+)

diff --git a/docs/pages/release_notes.md b/docs/pages/release_notes.md
index 39aef42caa..58bd741913 100644
--- a/docs/pages/release_notes.md
+++ b/docs/pages/release_notes.md
@@ -14,9 +14,16 @@ This is a {{ site.pmd.release_type }} release.
 
 ### 🚀 New and noteworthy
 
+### 🌟 New and changed rules
+#### New Rules
+* The new Java rule {%rule java/multithreading/AvoidSynchronizedStatement %} finds synchronization blocks that
+  could cause performance issues with virtual threads due to pinning.
+
 ### 🐛 Fixed Issues
 * apex-performance
   * [#5139](https://github.com/pmd/pmd/issues/5139): \[apex] OperationWithHighCostInLoop not firing in triggers
+* java-multithreading
+  * [#5175](https://github.com/pmd/pmd/issues/5175): \[java] Update AvoidSynchronizedAtMethodLevel message to mention ReentrantLock, new rule AvoidSynchronizedStatement
 * plsql-bestpractices
   * [#5132](https://github.com/pmd/pmd/issues/5132): \[plsql] TomKytesDespair - exception for more complex exception handler
 
@@ -32,6 +39,7 @@ This is a {{ site.pmd.release_type }} release.
     because this is an implementation class that should not be used directly.
 
 ### ✨ External Contributions
+* [#5175](https://github.com/pmd/pmd/pull/5175): \[java] Update AvoidSynchronizedAtMethodLevel message to mention ReentrantLock, new rule AvoidSynchronizedStatement - [Chas Honton](https://github.com/chonton) (@chonton)
 
 {% endtocmaker %}
 
diff --git a/pmd-java/src/main/resources/rulesets/java/quickstart.xml b/pmd-java/src/main/resources/rulesets/java/quickstart.xml
index 4afb964163..97eb2742da 100644
--- a/pmd-java/src/main/resources/rulesets/java/quickstart.xml
+++ b/pmd-java/src/main/resources/rulesets/java/quickstart.xml
@@ -279,6 +279,7 @@
 
 
     <!-- <rule ref="category/java/multithreading.xml/AvoidSynchronizedAtMethodLevel" /> -->
+    <!-- <rule ref="category/java/multithreading.xml/AvoidSynchronizedStatement" /> -->
     <rule ref="category/java/multithreading.xml/AvoidThreadGroup"/>
     <rule ref="category/java/multithreading.xml/AvoidUsingVolatile"/>
     <!-- <rule ref="category/java/multithreading.xml/DoNotUseThreads" /> -->