Merge loom into fibers

Author: AlanBateman

src/hotspot/share/services/diagnosticCommand.hpp

@@ -943,7 +943,8 @@ class VThreadSchedulerDCmd : public DCmd {
     return "Thread.vthread_scheduler";
   }
   static const char* description() {
-    return "Print the virtual thread scheduler.";
+    return "Print the virtual thread scheduler, and the delayed task schedulers that support "
+           "virtual threads doing timed operations.";
   }
   static const char* impact() { return "Low"; }
   virtual void execute(DCmdSource source, TRAPS);
@@ -956,7 +957,7 @@ class VThreadPollersDCmd : public DCmd {
     return "Thread.vthread_pollers";
   }
   static const char* description() {
-    return "Print the virtual thread I/O pollers.";
+    return "Print the I/O pollers that support virtual threads doing blocking network I/O operations.";
   }
   static const char* impact() { return "Low"; }
   virtual void execute(DCmdSource source, TRAPS);

src/java.base/share/classes/jdk/internal/vm/JcmdVThreadCommands.java

@@ -32,7 +32,8 @@
 import sun.nio.ch.Poller;
 
 /**
- * The implementation for the jcmd Thread.vthread_* diagnostic commands.
+ * The implementation for the jcmd Thread.vthread_* diagnostic commands. These methods are
+ * called from the "Attach Listener" thread.
  */
 public class JcmdVThreadCommands {
     private static final JavaLangAccess JLA = SharedSecrets.getJavaLangAccess();
@@ -47,22 +48,21 @@ private static byte[] printScheduler() {
 
         // virtual thread scheduler
         sb.append(JLA.virtualThreadDefaultScheduler())
-                .append(System.lineSeparator());
+          .append(System.lineSeparator());
 
         // break
         sb.append(System.lineSeparator());
 
         // delayed task schedulers
+        sb.append("Delayed task schedulers:").append(System.lineSeparator());
         var delayedTaskSchedulers = JLA.virtualThreadDelayedTaskSchedulers().toList();
-        sb.append("Delayed task schedulers:")
-                .append(System.lineSeparator());
-        for (int i = 0; i < delayedTaskSchedulers.size(); i++) {
-            sb.append('[')
-                    .append(i)
-                    .append("] ")
-                    .append(delayedTaskSchedulers.get(i))
-                    .append(System.lineSeparator());
-        }
+        IntStream.range(0, delayedTaskSchedulers.size())
+                .forEach(i -> sb.append('[')
+                                .append(i)
+                                .append("] ")
+                                .append(delayedTaskSchedulers.get(i))
+                                .append(System.lineSeparator()));
+
         return sb.toString().getBytes(StandardCharsets.UTF_8);
     }
 
@@ -78,30 +78,34 @@ private static byte[] printPollers() {
 
         if (masterPoller != null) {
             sb.append("Master I/O poller:")
-                    .append(System.lineSeparator())
-                    .append(masterPoller)
-                    .append(System.lineSeparator());
+              .append(System.lineSeparator())
+              .append(masterPoller)
+              .append(System.lineSeparator());
+
+            // break
             sb.append(System.lineSeparator());
         }
 
         sb.append("Read I/O pollers:");
         sb.append(System.lineSeparator());
         IntStream.range(0, readPollers.size())
                 .forEach(i -> sb.append('[')
-                        .append(i)
-                        .append("] ")
-                        .append(readPollers.get(i))
-                        .append(System.lineSeparator()));
+                                .append(i)
+                                .append("] ")
+                                .append(readPollers.get(i))
+                                .append(System.lineSeparator()));
+
+        // break
         sb.append(System.lineSeparator());
 
         sb.append("Write I/O pollers:");
         sb.append(System.lineSeparator());
         IntStream.range(0, writePollers.size())
                 .forEach(i -> sb.append('[')
-                        .append(i)
-                        .append("] ")
-                        .append(writePollers.get(i))
-                        .append(System.lineSeparator()));
+                                .append(i)
+                                .append("] ")
+                                .append(writePollers.get(i))
+                                .append(System.lineSeparator()));
 
         return sb.toString().getBytes(StandardCharsets.UTF_8);
     }

src/jdk.jcmd/share/man/jcmd.md

@@ -738,12 +738,13 @@ The following commands are available:
     -   `-l`: (Optional) Prints `java.util.concurrent` locks (BOOLEAN, false)
 
 `Thread.vthread_scheduler`
-:   Print the virtual thread scheduler.
+:   Print the virtual thread scheduler, and the delayed task schedulers that support
+    virtual threads doing timed operations.
 
     Impact: Low
 
 `Thread.vthread_pollers`
-:   Print the virtual thread I/O pollers.
+:   Print the I/O pollers that support virtual threads doing blocking network I/O operations.
 
     Impact: Low
 

test/hotspot/jtreg/serviceability/dcmd/thread/VThreadCommandsTest.java

@@ -79,9 +79,9 @@ void testVThreadPollers() throws Exception {
                 try (var listener = new ServerSocket()) {
                     InetAddress lb = InetAddress.getLoopbackAddress();
                     listener.bind(new InetSocketAddress(lb, 0));
-                    listener.setSoTimeout(1000);
+                    listener.setSoTimeout(200);
                     try (Socket s = listener.accept()) {
-                        fail("Connection from " + s.getRemoteSocketAddress());
+                        System.err.format("Connection from %s ??%n", s.getRemoteSocketAddress());
                     } catch (SocketTimeoutException e) {
                         // expected
                     }