Only close context that is active

Previously, SpringApplicationShutdownHook would call close() on any
registered application context even if it wasn't active as it had
already been closed. This could lead to deadlock if the context was
closed and System.exit was called during application context refresh.

This commit updates SpringApplicationShutdownHook so that it only
calls close() on active contexts. This prevents deadlock as it avoids
trying to sychronize on the context's startupShutdownMonitor on
the shutdown hook thread while it's still held on the main thread
which called System.exit and is waiting for all of the shutdown hooks
to complete.

Fixes gh-27049

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/SpringApplicationShutdownHook.java

@@ -125,6 +125,9 @@ void reset() {
 	 * @param context the context to clean
 	 */
 	private void closeAndWait(ConfigurableApplicationContext context) {
+		if (!context.isActive()) {
+			return;
+		}
 		context.close();
 		try {
 			int waited = 0;

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/SpringApplicationShutdownHookTests.java

@@ -26,10 +26,12 @@
 import org.awaitility.Awaitility;
 import org.junit.jupiter.api.Test;
 
+import org.springframework.beans.factory.InitializingBean;
 import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
 import org.springframework.beans.factory.support.DefaultListableBeanFactory;
 import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.context.support.AbstractApplicationContext;
+import org.springframework.context.support.GenericApplicationContext;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
@@ -91,6 +93,15 @@ void runWhenContextIsBeingClosedInAnotherThreadWaitsUntilContextIsInactive() thr
 		assertThat(finished).containsExactly(context, handlerAction);
 	}
 
+	@Test
+	void runDueToExitDuringRefreshWhenContextHasBeenClosedDoesNotDeadlock() throws InterruptedException {
+		GenericApplicationContext context = new GenericApplicationContext();
+		TestSpringApplicationShutdownHook shutdownHook = new TestSpringApplicationShutdownHook();
+		shutdownHook.registerApplicationContext(context);
+		context.registerBean(CloseContextAndExit.class, context, shutdownHook);
+		context.refresh();
+	}
+
 	@Test
 	void runWhenContextIsClosedDirectlyRunsHandlerActions() {
 		TestSpringApplicationShutdownHook shutdownHook = new TestSpringApplicationShutdownHook();
@@ -221,4 +232,28 @@ public void run() {
 
 	}
 
+	static class CloseContextAndExit implements InitializingBean {
+
+		private final ConfigurableApplicationContext context;
+
+		private final Runnable shutdownHook;
+
+		CloseContextAndExit(ConfigurableApplicationContext context, SpringApplicationShutdownHook shutdownHook) {
+			this.context = context;
+			this.shutdownHook = shutdownHook;
+		}
+
+		@Override
+		public void afterPropertiesSet() throws Exception {
+			this.context.close();
+			// Simulate System.exit by running the hook on a separate thread and waiting
+			// for it to complete
+			Thread thread = new Thread(this.shutdownHook);
+			thread.start();
+			thread.join(15000);
+			assertThat(thread.isAlive()).isFalse();
+		}
+
+	}
+
 }