8342905: Thread.setContextClassloader from thread in FJP commonPool task no longer works after JDK-8327501 redux

Reviewed-by: alanb

Author: Viktor Klang

src/java.base/share/classes/java/util/concurrent/ForkJoinPool.java

@@ -51,6 +51,8 @@
 import java.util.function.Predicate;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.locks.LockSupport;
+
+import jdk.internal.access.JavaLangAccess;
 import jdk.internal.access.JavaUtilConcurrentFJPAccess;
 import jdk.internal.access.SharedSecrets;
 import jdk.internal.misc.Unsafe;
@@ -1133,9 +1135,7 @@ static final class DefaultForkJoinWorkerThreadFactory
         implements ForkJoinWorkerThreadFactory {
         public final ForkJoinWorkerThread newThread(ForkJoinPool pool) {
             boolean isCommon = (pool.workerNamePrefix == null);
-            @SuppressWarnings("removal")
-            SecurityManager sm = System.getSecurityManager();
-            if (sm != null && isCommon)
+            if (isCommon && JLA.allowSecurityManager())
                 return newCommonWithACC(pool);
             else
                 return newRegularWithACC(pool);
@@ -1152,6 +1152,8 @@ public final ForkJoinWorkerThread newThread(ForkJoinPool pool) {
         @SuppressWarnings("removal")
         static volatile AccessControlContext regularACC, commonACC;
 
+        private static final JavaLangAccess JLA = SharedSecrets.getJavaLangAccess();
+
         @SuppressWarnings("removal")
         static ForkJoinWorkerThread newRegularWithACC(ForkJoinPool pool) {
             AccessControlContext acc = regularACC;