Add AllowUserSignalHandlers.

src/main/java/org/github/joa/JvmOptions.java

@@ -141,6 +141,17 @@ public class JvmOptions {
      */
     private String aggressiveOpts;
 
+    /**
+     * Option to allow the application to install signal handlers. Disabled by default.
+     * 
+     * For example:
+     * 
+     * <pre>
+     * -XX:+AllowUserSignalHandlers
+     * </pre>
+     */
+    private String allowUserSignalHandlers;
+
     /**
      * Option to enable/disable touching all java heap memory pages on JVM startup.
      * 
@@ -2047,6 +2058,7 @@ public class JvmOptions {
      * </pre>
      */
     private String softRefLRUPolicyMSPerMB;
+
     /**
      * The option for starting JDK Flight Recorder (JFR). For example:
      * 
@@ -2067,7 +2079,6 @@ public class JvmOptions {
      * </pre>
      */
     private String startFlightRecording;
-
     /**
      * Option to set the number of <code>String</code>s to pool in the String table to optimize memory.
      * 
@@ -3092,6 +3103,9 @@ public JvmOptions(JvmContext jvmContext) {
                 } else if (option.matches("^-XX:[\\-+]AggressiveOpts$")) {
                     aggressiveOpts = option;
                     key = "AggressiveOpts";
+                } else if (option.matches("^-XX:[\\-+]AllowUserSignalHandlers$")) {
+                    allowUserSignalHandlers = option;
+                    key = "AllowUserSignalHandlers";
                 } else if (option.matches("^-XX:[\\-+]AlwaysPreTouch$")) {
                     alwaysPreTouch = option;
                     key = "alwaysPreTouch";
@@ -4725,6 +4739,10 @@ public void doAnalysis() {
             if (JdkUtil.isOptionEnabled(aggressiveOpts)) {
                 addAnalysis(Analysis.INFO_AGGRESSIVE_OPTS_ENABLED);
             }
+            // Check for -XX:+AllowUserSignalHandlers
+            if (JdkUtil.isOptionEnabled(allowUserSignalHandlers)) {
+                addAnalysis(Analysis.INFO_ALLOW_USER_SIGNAL_HANDLERS_ENABLED);
+            }
             // Check for ZGC memory uncommitting disabled.
             if (JdkUtil.isOptionDisabled(zUncommit) || ((JdkUtil.isOptionEnabled(useZGc)
                     || jvmContext.getGarbageCollectors().contains(GarbageCollector.ZGC_GENERATIONAL)
@@ -4801,6 +4819,10 @@ public String getAggressiveOpts() {
         return aggressiveOpts;
     }
 
+    public String getAllowUserSignalHandlers() {
+        return allowUserSignalHandlers;
+    }
+
     public String getAlwaysPreTouch() {
         return alwaysPreTouch;
     }

src/main/java/org/github/joa/util/Analysis.java

@@ -133,6 +133,11 @@ public enum Analysis {
      */
     INFO_AGGRESSIVE_OPTS_ENABLED("info.aggressive.opts.enabled"),
 
+    /**
+     * Property key for allowing user signal handlers with -XX:+AllowUserSignalHandlers.
+     */
+    INFO_ALLOW_USER_SIGNAL_HANDLERS_ENABLED("info.allow.user.signal.handlers.enabled"),
+
     /**
      * Property key for biased locking disabled (-XX:-UseBiasedLocking) when it is enabled by default (or the default is
      * unknown) and {@link org.github.joa.domain.GarbageCollector#SHENANDOAH} is not identified.

src/main/resources/org/github/joa/analysis.properties

@@ -19,7 +19,8 @@ info.64.d64.redundant=The -d64 flag does not serve a purpose in JDK8 and is remo
 info.64.server.redundant=The -server flag no longer serves a purpose in JDK8+ and can be removed, as only the server JIT compiler is included in 64-bit JDKs.
 info.active.processor.count=The number of cpu/cores is being explicitly set with -XX:ActiveProcessorCount=N. Unless multiple JVMs and/or processes are collocated and competing for resources, it's generally best to remove this option and let the JVM determine cpu/cores from cgroup settings.
 info.aggressive.opts.enabled=-XX:+AggressiveOpts is not a recommended option. It's original intent was to enable/disable various experimental performance optimizations; however, the meaning has varied over time, with functionality removed or integrated. Currently, the only effect is setting 'AutoBoxCacheMax' to 20000 and 'BiasedLockingStartupDelay' to 500. These are questionable settings, but if they are desired, it is recommended to set them directly. Disabled by default, deprecated in JDK11, and removed in JDK17.
-info.biased.locking.disabled=Biased locking is explicity disabled with -XX-UseBiasedLocking. Biased locking is a threading optimization that benefits objects that are only locked by a single thread. Enabled by default in JDK8/11, disabled by default and dreprecated in JDK17, and removed in JDK21.
+info.allow.user.signal.handlers.enabled=User signal handlers are allowed with -XX:+AllowUserSignalHandlers.
+info.biased.locking.disabled=Biased locking is explicitly disabled with -XX-UseBiasedLocking. Biased locking is a threading optimization that benefits objects that are only locked by a single thread. Enabled by default in JDK8/11, disabled by default and dreprecated in JDK17, and removed in JDK21.
 info.biased.locking.disabled.redundant=-XX-UseBiasedLocking is redundant (disabled by default) and can be removed. Biased locking is a threading optimization that benefits objects that are only locked by a single thread. Dreprecated in JDK17 and removed in JDK21.
 info.biased.locking.enabled=Biased locking is explicitly enabled with -XX+UseBiasedLocking. Biased locking is a threading optimization that benefits objects that are only locked by a single thread. Enabled by default in JDK8/11, disabled by default and dreprecated in JDK17, and removed in JDK21.
 info.biased.locking.enabled.redundant=-XX+UseBiasedLocking is redundant (enabled by default) and can be removed. Biased locking is a threading optimization that benefits objects that are only locked by a single thread. Disabled by default and dreprecated in JDK17 and removed in JDK21.

src/test/java/org/github/joa/TestJvmOptions.java

@@ -76,6 +76,15 @@ void testAgentLib() {
                 "JDPA socket transport (debugging) not correct.");
     }
 
+    @Test
+    void testAllowUserSignalHandlers() {
+        String opts = "-Xms1g -XX:+AllowUserSignalHandlers -Xmx1g";
+        JvmContext context = new JvmContext(opts);
+        JvmOptions jvmOptions = new JvmOptions(context);
+        assertEquals("-XX:+AllowUserSignalHandlers", jvmOptions.getAllowUserSignalHandlers(),
+                "AllowUserSignalHandlers not correct.");
+    }
+
     @Test
     void testBiasedLockingStartupDelay() {
         String opts = "-Xms1000m -XX:BiasedLockingStartupDelay=500 -Xmx1500m";

src/test/java/org/github/joa/util/TestAnalysis.java

@@ -53,6 +53,17 @@ void testAggressiveOptsEnabled() {
                 Analysis.INFO_AGGRESSIVE_OPTS_ENABLED + " analysis not identified.");
     }
 
+    @Test
+    void testAllowUserSignalHandlersEnabled() {
+        String opts = "-XX:+AllowUserSignalHandlers";
+        JvmContext context = new JvmContext(opts);
+        context.setContainer(true);
+        JvmOptions jvmOptions = new JvmOptions(context);
+        jvmOptions.doAnalysis();
+        assertTrue(jvmOptions.hasAnalysis(Analysis.INFO_ALLOW_USER_SIGNAL_HANDLERS_ENABLED.getKey()),
+                Analysis.INFO_ALLOW_USER_SIGNAL_HANDLERS_ENABLED + " analysis not identified.");
+    }
+
     @Test
     void testAlwaysPreTouchContainer() {
         String opts = "-XX:+AlwaysPreTouch";