Remove some synchronization in Reference to avoid deadlock

Issue #13823

Signed-off-by: Peter Shipton <[email protected]>

Author: pshipton

jcl/src/java.base/share/classes/java/lang/ref/Reference.java

@@ -60,7 +60,7 @@ public abstract sealed class Reference<T> extends Object permits PhantomReferenc
 
 	private T referent;
 	private ReferenceQueue queue;
-	private int state;
+	private volatile int state;
 
 	/* jdk.lang.ref.disableClearBeforeEnqueue property allow reverting to the old behavior(non clear before enqueue)
 	 *  defer initializing the immutable variable to avoid bootstrap error
@@ -181,9 +181,7 @@ public T get() {
 	@Deprecated(since="16")
 	/*[ENDIF] JAVA_SPEC_VERSION >= 16 */
 	public boolean isEnqueued () {
-		synchronized(this) {
-			return state == STATE_ENQUEUED;
-		}
+		return state == STATE_ENQUEUED;
 	}
 
 	/**
@@ -255,10 +253,7 @@ void initReference (T r, ReferenceQueue q) {
 	 * Set the enqueued field to false.
 	 */
 	void dequeue() {
-		/*[PR 112508] not synchronized, so isEnqueued() could return wrong result */
-		synchronized(this) {
-			state = STATE_CLEARED;
-		}
+		state = STATE_CLEARED;
 	}
 
 	/*[IF JAVA_SPEC_VERSION >= 9]*/