test/hotspot/jtreg/vmTestbase/nsk/jdi/ObjectReference/referringObjects/referringObjects001/referringObjects001.java

*** 49,58 ****
--- 49,59 ----
   *         done
   *     - Debugger VM
   *         create references of all possible types to single object, ObjectReference.referringObjects should return only
   *         referrers with supported type(Strong, PhantomReference, SoftReference, WeakReference)
   *
+  * @requires vm.gc != "Z"
   * @library /vmTestbase
   *          /test/lib
   * @run driver jdk.test.lib.FileInstaller . .
   * @build nsk.jdi.ObjectReference.referringObjects.referringObjects001.referringObjects001
   *        nsk.share.jdi.TestClass1
*** 149,158 ****
--- 150,164 ----
          if (includedInInstancesCount)
              expectedInstanceCount = createInstanceCount;
          else
              expectedInstanceCount = 0;
  
+         // Note! This test is broken, in the sense that it incorrectly assumes
+         // that no GC can happen before it walks the heap. In practice, it seems
+         // to only affect this test when using ZGC. However, this test will also
+         // fail when using other GCs if an explicit GC is done here.
+ 
          checkDebugeeAnswer_instanceCounts(className, expectedInstanceCount, objectsToFilter);
          checkDebugeeAnswer_instances_referringObjects(objectsToFilter, className, expectedInstanceCount, includedInReferrersCount, referrerCount);
  
          // delete half of referrers