8258753: StartTlsResponse.close() hangs due to synchronization issues

Reviewed-by: coffeys

Author: Prajwal Kumaraswamy

src/java.base/share/classes/sun/security/ssl/SSLSocketImpl.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1996, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1996, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -1784,17 +1784,23 @@ private void waitForClose() throws IOException {
             SSLLogger.fine("wait for close_notify or alert");
         }
 
-        while (!conContext.isInboundClosed()) {
-            try {
-                Plaintext plainText = decode(null);
-                // discard and continue
-                if (SSLLogger.isOn && SSLLogger.isOn("ssl")) {
-                    SSLLogger.finest(
-                        "discard plaintext while waiting for close", plainText);
+        appInput.readLock.lock();
+        try {
+            while (!conContext.isInboundClosed()) {
+                try {
+                    Plaintext plainText = decode(null);
+                    // discard and continue
+                    if (SSLLogger.isOn && SSLLogger.isOn("ssl")) {
+                        SSLLogger.finest(
+                                "discard plaintext while waiting for close",
+                                plainText);
+                    }
+                } catch (Exception e) {   // including RuntimeException
+                    handleException(e);
                 }
-            } catch (Exception e) {   // including RuntimeException
-                handleException(e);
             }
+        } finally {
+            appInput.readLock.unlock();
         }
     }
 }