backport 44d62c8e21fb09381f9f86a081f70549cc321b1e

Author: GoeLin

src/jdk.attach/linux/classes/sun/tools/attach/VirtualMachineImpl.java

@@ -35,6 +35,8 @@
 import java.nio.file.Path;
 import java.nio.file.Paths;
 
+import java.util.Optional;
+
 import java.util.regex.Pattern;
 
 import static java.nio.charset.StandardCharsets.UTF_8;
@@ -368,7 +370,11 @@ private static boolean checkCatchesAndSendQuitTo(int pid, boolean throwIfNotRead
         if (okToSendQuit) {
             sendQuitTo(pid);
         } else if (throwIfNotReady) {
-            final var cmdline = Files.lines(procPid.resolve("cmdline")).findFirst();
+            Optional<String> cmdline = Optional.empty();
+
+            try (final var clf = Files.lines(procPid.resolve("cmdline"))) {
+                cmdline = clf.findFirst();
+            }
 
             var cmd = "null"; // default
 

test/hotspot/jtreg/containers/docker/TestJcmdWithSideCar.java

@@ -43,8 +43,8 @@
 import java.io.IOException;
 import java.io.InputStreamReader;
 import java.nio.file.Paths;
-import java.util.Arrays;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collections;
 import java.util.EnumSet;
 import java.util.List;
@@ -53,7 +53,9 @@
 import java.util.function.Consumer;
 import java.util.regex.Pattern;
 import java.util.stream.Collectors;
+
 import jdk.test.lib.Container;
+import jdk.test.lib.Platform;
 import jdk.test.lib.Utils;
 import jdk.test.lib.containers.docker.Common;
 import jdk.test.lib.containers.docker.DockerRunOptions;
@@ -109,6 +111,11 @@ public static void main(String[] args) throws Exception {
                 mainContainer.waitForMainMethodStart(TIME_TO_WAIT_FOR_MAIN_METHOD_START);
 
                 for (AttachStrategy attachStrategy : EnumSet.allOf(AttachStrategy.class)) {
+                    if (attachStrategy == AttachStrategy.ACCESS_TMP_VIA_PROC_ROOT &&
+                        elevated && !Platform.isRoot()) {
+                        // Elevated attach via proc/root not yet supported.
+                        continue;
+                    }
                     long mainProcPid = testCase01(attachStrategy, elevated);
 
                     // Excluding the test case below until JDK-8228850 is fixed