diff --git a/dd-java-agent/instrumentation/java/java-lang/java-lang-21.0/src/main/java/datadog/trace/instrumentation/java/lang/jdk21/VirtualThreadInstrumentation.java b/dd-java-agent/instrumentation/java/java-lang/java-lang-21.0/src/main/java/datadog/trace/instrumentation/java/lang/jdk21/VirtualThreadInstrumentation.java index d1ad6e30ebc..6ba368bbfbf 100644 --- a/dd-java-agent/instrumentation/java/java-lang/java-lang-21.0/src/main/java/datadog/trace/instrumentation/java/lang/jdk21/VirtualThreadInstrumentation.java +++ b/dd-java-agent/instrumentation/java/java-lang/java-lang-21.0/src/main/java/datadog/trace/instrumentation/java/lang/jdk21/VirtualThreadInstrumentation.java @@ -66,11 +66,14 @@ public final class VirtualThreadInstrumentation extends InstrumenterModule.Conte Instrumenter.HasMethodAdvice, ExcludeFilterProvider { - // Preload classes used by Context.swap() to avoid class loading on the virtual thread mount path. - // DatadogClassLoader loads these from a JarFile using synchronized I/O, which pins - // virtual thread carrier threads and can deadlock the application. + /** + * Preloads mount/unmount helpers to avoid class loading during a JVMTI mount transition. Class + * loading can wait for that same transition to finish, or pin carriers in synchronized jar I/O. + */ private static final String[] PRELOAD_CLASS_NAMES = { - "datadog.trace.core.scopemanager.ScopeContext", "datadog.trace.core.scopemanager.ScopeStack" + VIRTUAL_THREAD_STATE_CLASS_NAME, + "datadog.trace.core.scopemanager.ScopeContext", + "datadog.trace.core.scopemanager.ScopeStack" }; public VirtualThreadInstrumentation() { diff --git a/dd-smoke-tests/concurrent/java-21/src/main/java/datadog/smoketest/concurrent/VirtualThreadStartup.java b/dd-smoke-tests/concurrent/java-21/src/main/java/datadog/smoketest/concurrent/VirtualThreadStartup.java new file mode 100644 index 00000000000..085253d69e5 --- /dev/null +++ b/dd-smoke-tests/concurrent/java-21/src/main/java/datadog/smoketest/concurrent/VirtualThreadStartup.java @@ -0,0 +1,12 @@ +package datadog.smoketest.concurrent; + +public class VirtualThreadStartup { + public static void main(String[] args) throws InterruptedException { + boolean[] ran = {false}; + Thread thread = Thread.startVirtualThread(() -> ran[0] = true); + thread.join(); + if (!ran[0]) { + throw new AssertionError("Virtual thread did not execute"); + } + } +} diff --git a/dd-smoke-tests/concurrent/java-21/src/test/java/datadog/smoketest/concurrent/VirtualThreadStartupSmokeTest.java b/dd-smoke-tests/concurrent/java-21/src/test/java/datadog/smoketest/concurrent/VirtualThreadStartupSmokeTest.java new file mode 100644 index 00000000000..e53bd644316 --- /dev/null +++ b/dd-smoke-tests/concurrent/java-21/src/test/java/datadog/smoketest/concurrent/VirtualThreadStartupSmokeTest.java @@ -0,0 +1,28 @@ +package datadog.smoketest.concurrent; + +import static datadog.smoketest.backend.AgentBackend.testAgent; +import static java.util.concurrent.TimeUnit.SECONDS; + +import datadog.smoketest.SmokeCliApp; +import org.junit.jupiter.api.Test; +import org.junit.jupiter.api.extension.RegisterExtension; + +class VirtualThreadStartupSmokeTest { + @RegisterExtension + static final SmokeCliApp app = + SmokeCliApp.named("virtual-thread-startup") + .mainClass( + "datadog.smoketest.concurrent.VirtualThreadStartup", + System.getProperty("datadog.smoketest.shadowJar.path")) + .jvmArgs( + "-Djdk.virtualThreadScheduler.parallelism=1", + "-Djdk.virtualThreadScheduler.maxPoolSize=1") + .backend(testAgent()) + .skipTelemetryCheck() + .build(); + + @Test + void startsVirtualThreadWithoutActiveContext() { + app.assertCompletesWithValue(30, SECONDS, 0); + } +}