From 202fd421f7e8b0f4a9c7393d1045e879acd13e64 Mon Sep 17 00:00:00 2001
From: Leonid Mesnik <lmesnik@openjdk.org>
Date: Tue, 17 Sep 2024 22:36:37 +0000
Subject: [PATCH] 8340213: jcmd VM.events ignores max argument

Reviewed-by: szaldana, cjplummer, amenkov, mli
---
 .../share/services/diagnosticCommand.cpp      |  1 -
 .../serviceability/dcmd/vm/EventsTest.java    | 24 ++++++++++++++++++-
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/src/hotspot/share/services/diagnosticCommand.cpp b/src/hotspot/share/services/diagnosticCommand.cpp
index 7a2c0838146..4d4a5239b3b 100644
--- a/src/hotspot/share/services/diagnosticCommand.cpp
+++ b/src/hotspot/share/services/diagnosticCommand.cpp
@@ -899,7 +899,6 @@ void EventLogDCmd::execute(DCmdSource source, TRAPS) {
   int max = -1;
   if (max_value != nullptr) {
     char* endptr = nullptr;
-    int max;
     if (!parse_integer(max_value, &max)) {
       output()->print_cr("Invalid max option: \"%s\".", max_value);
       return;
diff --git a/test/hotspot/jtreg/serviceability/dcmd/vm/EventsTest.java b/test/hotspot/jtreg/serviceability/dcmd/vm/EventsTest.java
index b5fca58a5c5..9828a8990e0 100644
--- a/test/hotspot/jtreg/serviceability/dcmd/vm/EventsTest.java
+++ b/test/hotspot/jtreg/serviceability/dcmd/vm/EventsTest.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2019, 2024, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -25,6 +25,7 @@ import jdk.test.lib.dcmd.CommandExecutor;
 import jdk.test.lib.dcmd.JMXExecutor;
 import jdk.test.lib.process.OutputAnalyzer;
 import org.testng.annotations.Test;
+import org.testng.Assert;
 
 /*
  * @test
@@ -38,6 +39,9 @@ import org.testng.annotations.Test;
  */
 public class EventsTest {
 
+    // MAX should be less than number of actually recorded events
+    private static int MAX = 9;
+
     static String buildHeaderPattern(String logname) {
         return "^" + logname + ".*\\(\\d+ events\\):";
     }
@@ -64,9 +68,27 @@ public class EventsTest {
         output.stdoutShouldNotMatch(buildHeaderPattern("Classes unloaded"));
     }
 
+    public void run_max(CommandExecutor executor) {
+        OutputAnalyzer output = executor.execute("VM.events max=" + MAX);
+        long lines = output.asLines().stream().filter(x -> x.contains("Loading class")).count();
+        Assert.assertTrue(lines == MAX, "There are should be " + MAX + " lines");
+    }
+
+    public void run_max_selected(CommandExecutor executor) {
+        OutputAnalyzer output = executor.execute("VM.events log=load max=" + MAX);
+        output.stdoutShouldMatch(buildHeaderPattern("Classes loaded"));
+        long lines = output.asLines().stream().filter(x -> x.contains("Loading class")).count();
+        Assert.assertTrue(lines == MAX, "There are should be " + MAX + " lines");
+        output.stdoutShouldNotMatch(buildHeaderPattern("Events"));
+        output.stdoutShouldNotMatch(buildHeaderPattern("Compilation"));
+    }
+
+
     @Test
     public void jmx() {
         run_all(new JMXExecutor());
         run_selected(new JMXExecutor());
+        run_max(new JMXExecutor());
+        run_max_selected(new JMXExecutor());
     }
 }