8372198: Avoid closing PlainHttpConnection while holding a lock

src/java.net.http/share/classes/jdk/internal/net/http/ConnectionPool.java

@@ -205,32 +205,38 @@ void returnToPool(HttpConnection conn, Deadline now, long keepAlive) {
 
         // it's possible that cleanup may have been called.
         HttpConnection toClose = null;
+        boolean stopping = false;
         stateLock.lock();
         try {
             if (cleanup.isDone()) {
                 return;
-            } else if (stopped) {
-                conn.close();
-                return;
-            }
-            if (MAX_POOL_SIZE > 0 && expiryList.size() >= MAX_POOL_SIZE) {
-                toClose = expiryList.removeOldest();
-                if (toClose != null) removeFromPool(toClose);
-            }
-            if (conn instanceof PlainHttpConnection) {
-                putConnection(conn, plainPool);
+            } else if (stopping = stopped) {
+                toClose = conn;
             } else {
-                assert conn.isSecure();
-                putConnection(conn, sslPool);
+                if (MAX_POOL_SIZE > 0 && expiryList.size() >= MAX_POOL_SIZE) {
+                    toClose = expiryList.removeOldest();
+                    if (toClose != null) removeFromPool(toClose);
+                }
+                if (conn instanceof PlainHttpConnection) {
+                    putConnection(conn, plainPool);
+                } else {
+                    assert conn.isSecure();
+                    putConnection(conn, sslPool);
+                }
+                expiryList.add(conn, now, keepAlive);
             }
-            expiryList.add(conn, now, keepAlive);
         } finally {
             stateLock.unlock();
         }
         if (toClose != null) {
             if (debug.on()) {
-                debug.log("Maximum pool size reached: removing oldest connection %s",
-                          toClose.dbgString());
+                if (stopping) {
+                    debug.log("Stopping: close connection %s",
+                            toClose.dbgString());
+                } else {
+                    debug.log("Maximum pool size reached: removing oldest connection %s",
+                            toClose.dbgString());
+                }
             }
             close(toClose);
         }

src/java.net.http/share/classes/jdk/internal/net/http/HttpClientImpl.java

@@ -1333,6 +1333,13 @@ String getName() {
 
         // Only called by the selector manager thread
         private void shutdown() {
+            // first stop the client to avoid seeing exceptions
+            // about "selector manager closed"
+            Log.logTrace("{0}: stopping", owner.dbgTag);
+            try {
+                owner.stop();
+            } catch (Throwable ignored) {
+            }
             try {
                 lock.lock();
                 try {
@@ -1345,6 +1352,7 @@ private void shutdown() {
                 }
             } catch (IOException ignored) {
             } finally {
+                // cleanup anything that might have been left behind
                 owner.stop();
             }
         }

src/java.net.http/share/classes/jdk/internal/net/http/PlainHttpConnection.java

@@ -311,20 +311,20 @@ void close(Throwable cause) {
             var connectTimerEvent = this.connectTimerEvent;
             if (connectTimerEvent != null)
                 client().cancelTimer(connectTimerEvent);
-            if (Log.channel()) {
-                Log.logChannel("Closing channel: " + chan);
-            }
-            try {
-                tube.signalClosed(errorRef.get());
-                chan.close();
-            } finally {
-                client().connectionClosed(this);
-            }
+        } finally {
+            stateLock.unlock();
+        }
+        if (Log.channel()) {
+            Log.logChannel("Closing channel: " + chan);
+        }
+        try {
+            tube.signalClosed(errorRef.get());
+            chan.close();
         } catch (IOException e) {
             debug.log("Closing resulted in " + e);
             Log.logTrace("Closing resulted in " + e);
         } finally {
-            stateLock.unlock();
+            client().connectionClosed(this);
         }
     }