--- old/src/hotspot/share/memory/metaspaceShared.cpp	2020-06-08 15:04:01.547243681 -0700
+++ new/src/hotspot/share/memory/metaspaceShared.cpp	2020-06-08 15:04:01.411238562 -0700
@@ -36,6 +36,7 @@
 #include "classfile/systemDictionary.hpp"
 #include "classfile/systemDictionaryShared.hpp"
 #include "code/codeCache.hpp"
+#include "gc/shared/gcLocker.hpp"
 #include "gc/shared/softRefPolicy.hpp"
 #include "interpreter/bytecodeStream.hpp"
 #include "interpreter/bytecodes.hpp"
@@ -1229,6 +1230,7 @@
   void print_heap_region_stats(GrowableArray<MemRegion> *heap_mem,
                                const char *name, size_t total_size);
   void relocate_to_requested_base_address(CHeapBitMap* ptrmap);
+  void run_gc();
 
 public:
 
@@ -1636,7 +1638,26 @@
   }
 }
 
+void VM_PopulateDumpSharedSpace::run_gc() {
+  if (HeapShared::is_heap_object_archiving_allowed()) {
+    // Avoid fragmentation while archiving heap objects.
+    // We do this inside a safepoint, so that no further allocation can happen after GC
+    // has finished.
+    if (GCLocker::is_active()) {
+      // This should not happen during -Xshare:dump. If you see this, probably the Java core lib
+      // has been modified such that JNI code is executed in some clean up threads after
+      // we have finished class loading.
+      log_warning(cds)("GC locker is held; GC is skipped. This may produce suboptimal archive heap regions.");
+    } else {
+      log_info(cds)("Run GC ...");
+      Universe::heap()->collect_as_vm_thread(GCCause::_archive_time_gc);
+      log_info(cds)("Run GC done");
+    }
+  }
+}
+
 void VM_PopulateDumpSharedSpace::doit() {
+  run_gc();
   CHeapBitMap ptrmap;
   MetaspaceShared::initialize_ptr_marker(&ptrmap);
 
@@ -1955,14 +1976,9 @@
     link_and_cleanup_shared_classes(CATCH);
     log_info(cds)("Rewriting and linking classes: done");
 
-    if (HeapShared::is_heap_object_archiving_allowed()) {
-      // Avoid fragmentation while archiving heap objects.
-      Universe::heap()->soft_ref_policy()->set_should_clear_all_soft_refs(true);
-      Universe::heap()->collect(GCCause::_archive_time_gc);
-      Universe::heap()->soft_ref_policy()->set_should_clear_all_soft_refs(false);
-    }
-
     VM_PopulateDumpSharedSpace op;
+    MutexLocker ml(THREAD, HeapShared::is_heap_object_archiving_allowed() ?
+                   Heap_lock : NULL);     // needed for collect_as_vm_thread
     VMThread::execute(&op);
   }
 }