Refactor to reduce pinning in HTTP/2 code when using virtual threads

java/org/apache/coyote/http2/StreamProcessor.java

@@ -22,6 +22,8 @@
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.Set;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
 
 import jakarta.servlet.ServletConnection;
 import jakarta.servlet.http.HttpServletResponse;
@@ -55,6 +57,7 @@ class StreamProcessor extends AbstractProcessor {
 
     private static final Set<String> H2_PSEUDO_HEADERS_REQUEST = new HashSet<>();
 
+    private final Lock processLock = new ReentrantLock();
     private final Http2UpgradeHandler handler;
     private final Stream stream;
     private SendfileData sendfileData = null;
@@ -77,8 +80,9 @@ class StreamProcessor extends AbstractProcessor {
 
     final void process(SocketEvent event) {
         try {
-            // FIXME: the regular processor syncs on socketWrapper, but here this deadlocks
-            synchronized (this) {
+            // Note: The regular processor uses the socketWrapper lock, but using that here triggers a deadlock
+            processLock.lock();
+            try {
                 // HTTP/2 equivalent of AbstractConnectionHandler#process() without the
                 // socket <-> processor mapping
                 SocketState state = SocketState.CLOSED;
@@ -134,6 +138,8 @@ final void process(SocketEvent event) {
                         recycle();
                     }
                 }
+            } finally {
+                processLock.unlock();
             }
         } finally {
             handler.executeQueuedStream();

webapps/docs/changelog.xml

@@ -147,6 +147,10 @@
         <code>certificateKeystoreFile</code> attribute of an
         <code>SSLHostConfigCertificate</code> instance. (markt)
       </fix>
+      <scode>
+        Refactor HTTP/2 implementation to reduce pinning when using virtual
+        threads. (markt)
+      </scode>
     </changelog>
   </subsection>
   <subsection name="WebSocket">