--- a/hotspot/src/share/vm/classfile/classLoaderData.cpp	Wed Sep 03 14:43:49 2014 +0200
+++ b/hotspot/src/share/vm/classfile/classLoaderData.cpp	Wed Sep 03 19:13:18 2014 -0400
@@ -776,7 +776,7 @@
   // mark metadata seen on the stack and code cache so we can delete
   // unneeded entries.
   bool has_redefined_a_class = JvmtiExport::has_redefined_a_class();
-  MetadataOnStackMark md_on_stack;
+  MetadataOnStackMark md_on_stack(has_redefined_a_class);
   if (has_redefined_a_class) {
     // purge_previous_versions also cleans weak method links. Because
     // one method's MDO can reference another method from another

--- a/hotspot/src/share/vm/classfile/metadataOnStackMark.cpp	Wed Sep 03 14:43:49 2014 +0200
+++ b/hotspot/src/share/vm/classfile/metadataOnStackMark.cpp	Wed Sep 03 19:13:18 2014 -0400
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2013, 2014, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -41,7 +41,7 @@
 // Walk metadata on the stack and mark it so that redefinition doesn't delete
 // it.  Class unloading also walks the previous versions and might try to
 // delete it, so this class is used by class unloading also.
-MetadataOnStackMark::MetadataOnStackMark() {
+MetadataOnStackMark::MetadataOnStackMark(bool has_redefined_a_class) {
   assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
   NOT_PRODUCT(_is_active = true;)
   if (_marked_objects == NULL) {
@@ -49,7 +49,7 @@
   }
 
   Threads::metadata_do(Metadata::mark_on_stack);
-  if (JvmtiExport::has_redefined_a_class()) {
+  if (has_redefined_a_class) {
     CodeCache::alive_nmethods_do(nmethod::mark_on_stack);
   }
   CompileBroker::mark_on_stack();

--- a/hotspot/src/share/vm/classfile/metadataOnStackMark.hpp	Wed Sep 03 14:43:49 2014 +0200
+++ b/hotspot/src/share/vm/classfile/metadataOnStackMark.hpp	Wed Sep 03 19:13:18 2014 -0400
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2013, 2014, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -37,7 +37,7 @@
 class MetadataOnStackMark : public StackObj {
   NOT_PRODUCT(static bool _is_active;)
  public:
-  MetadataOnStackMark();
+  MetadataOnStackMark(bool has_redefined_a_class);
   ~MetadataOnStackMark();
   static void record(Metadata* m);
 };

--- a/hotspot/src/share/vm/code/nmethod.cpp	Wed Sep 03 14:43:49 2014 +0200
+++ b/hotspot/src/share/vm/code/nmethod.cpp	Wed Sep 03 19:13:18 2014 -0400
@@ -2062,7 +2062,7 @@
                "metadata must be found in exactly one place");
         if (r->metadata_is_immediate() && r->metadata_value() != NULL) {
           Metadata* md = r->metadata_value();
-          f(md);
+          if (md != _method) f(md);
         }
       } else if (iter.type() == relocInfo::virtual_call_type) {
         // Check compiledIC holders associated with this nmethod
@@ -2087,9 +2087,6 @@
     Metadata* md = *p;
     f(md);
   }
-
-  // Call function Method*, not embedded in these other places.
-  if (_method != NULL) f(_method);
 }
 
 void nmethod::oops_do(OopClosure* f, bool allow_zombie) {

--- a/hotspot/src/share/vm/memory/universe.cpp	Wed Sep 03 14:43:49 2014 +0200
+++ b/hotspot/src/share/vm/memory/universe.cpp	Wed Sep 03 19:13:18 2014 -0400
@@ -1256,8 +1256,8 @@
     // Deoptimize all activations depending on marked nmethods
     Deoptimization::deoptimize_dependents();
 
-    // Make the dependent methods not entrant (in VM_Deoptimize they are made zombies)
-    CodeCache::make_marked_nmethods_not_entrant();
+    // Make the dependent methods zombies (like VM_Deoptimize)
+    CodeCache::make_marked_nmethods_zombies();
   }
 }
 #endif // HOTSWAP

--- a/hotspot/src/share/vm/oops/instanceKlass.cpp	Wed Sep 03 14:43:49 2014 +0200
+++ b/hotspot/src/share/vm/oops/instanceKlass.cpp	Wed Sep 03 19:13:18 2014 -0400
@@ -2439,16 +2439,6 @@
     assert(breakpoints() == 0x0, "should have cleared breakpoints");
   }
 
-  // deallocate information about previous versions
-  if (_previous_versions != NULL) {
-    for (int i = _previous_versions->length() - 1; i >= 0; i--) {
-      PreviousVersionNode * pv_node = _previous_versions->at(i);
-      delete pv_node;
-    }
-    delete _previous_versions;
-    _previous_versions = NULL;
-  }
-
   // deallocate the cached class file
   if (_cached_class_file != NULL) {
     os::free(_cached_class_file, mtClass);
@@ -3022,16 +3012,17 @@
   st->print(BULLET"field type annotations:  "); fields_type_annotations()->print_value_on(st); st->cr();
   {
     bool have_pv = false;
-    PreviousVersionWalker pvw(Thread::current(), (InstanceKlass*)this);
-    for (PreviousVersionNode * pv_node = pvw.next_previous_version();
-         pv_node != NULL; pv_node = pvw.next_previous_version()) {
+    // previous versions are linked together through the InstanceKlass
+    for (InstanceKlass* pv_node = _previous_versions;
+         pv_node != NULL;
+         pv_node = pv_node->previous_versions()) {
       if (!have_pv)
         st->print(BULLET"previous version:  ");
       have_pv = true;
-      pv_node->prev_constant_pool()->print_value_on(st);
+      pv_node->constants()->print_value_on(st);
     }
     if (have_pv) st->cr();
-  } // pvw is cleaned up
+  }
 
   if (generic_signature() != NULL) {
     st->print(BULLET"generic signature: ");
@@ -3445,92 +3436,92 @@
 // RedefineClasses() support for previous versions:
 
 // Purge previous versions
-static void purge_previous_versions_internal(InstanceKlass* ik, int emcp_method_count) {
+void InstanceKlass::purge_previous_versions(InstanceKlass* ik) {
   if (ik->previous_versions() != NULL) {
     // This klass has previous versions so see what we can cleanup
     // while it is safe to do so.
 
     int deleted_count = 0;    // leave debugging breadcrumbs
     int live_count = 0;
-    ClassLoaderData* loader_data = ik->class_loader_data() == NULL ?
-                       ClassLoaderData::the_null_class_loader_data() :
-                       ik->class_loader_data();
+    ClassLoaderData* loader_data = ik->class_loader_data();
+    assert(loader_data != NULL, "should never be null");
 
     // RC_TRACE macro has an embedded ResourceMark
-    RC_TRACE(0x00000200, ("purge: %s: previous version length=%d",
-      ik->external_name(), ik->previous_versions()->length()));
-
-    for (int i = ik->previous_versions()->length() - 1; i >= 0; i--) {
-      // check the previous versions array
-      PreviousVersionNode * pv_node = ik->previous_versions()->at(i);
-      ConstantPool* cp_ref = pv_node->prev_constant_pool();
-      assert(cp_ref != NULL, "cp ref was unexpectedly cleared");
-
-      ConstantPool* pvcp = cp_ref;
+    RC_TRACE(0x00000200, ("purge: %s: previous versions", ik->external_name()));
+
+    // previous versions are linked together through the InstanceKlass
+    InstanceKlass* pv_node = ik->previous_versions();
+    InstanceKlass* last = ik;
+    int version = 0;
+
+    // check the previous versions list
+    for (; pv_node != NULL; ) {
+
+      ConstantPool* pvcp = pv_node->constants();
+      assert(pvcp != NULL, "cp ref was unexpectedly cleared");
+
       if (!pvcp->on_stack()) {
         // If the constant pool isn't on stack, none of the methods
-        // are executing.  Delete all the methods, the constant pool and
-        // and this previous version node.
-        GrowableArray<Method*>* method_refs = pv_node->prev_EMCP_methods();
-        if (method_refs != NULL) {
-          for (int j = method_refs->length() - 1; j >= 0; j--) {
-            Method* method = method_refs->at(j);
-            assert(method != NULL, "method ref was unexpectedly cleared");
-            method_refs->remove_at(j);
-            // method will be freed with associated class.
-          }
-        }
-        // Remove the constant pool
-        delete pv_node;
-        // Since we are traversing the array backwards, we don't have to
-        // do anything special with the index.
-        ik->previous_versions()->remove_at(i);
+        // are executing.  Unlink this previous_version.
+        // The previous version InstanceKlass is on the ClassLoaderData deallocate list
+        // so will be deallocated during the next phase of class unloading.
+        pv_node = pv_node->previous_versions();
+        last->link_previous_versions(pv_node);
         deleted_count++;
+        version++;
         continue;
       } else {
-        RC_TRACE(0x00000200, ("purge: previous version @%d is alive", i));
+        RC_TRACE(0x00000200, ("purge: previous version " INTPTR_FORMAT " is alive",
+                              pv_node));
         assert(pvcp->pool_holder() != NULL, "Constant pool with no holder");
         guarantee (!loader_data->is_unloading(), "unloaded classes can't be on the stack");
         live_count++;
       }
 
-      // At least one method is live in this previous version, clean out
-      // the others or mark them as obsolete.
-      GrowableArray<Method*>* method_refs = pv_node->prev_EMCP_methods();
+      // At least one method is live in this previous version so clean its MethodData.
+      // Reset dead EMCP methods not to get breakpoints.
+      // All methods are deallocated when all of the methods for this class are no
+      // longer running.
+      Array<Method*>* method_refs = pv_node->methods();
       if (method_refs != NULL) {
         RC_TRACE(0x00000200, ("purge: previous methods length=%d",
           method_refs->length()));
-        for (int j = method_refs->length() - 1; j >= 0; j--) {
+        for (int j = 0; j < method_refs->length(); j++) {
           Method* method = method_refs->at(j);
-          assert(method != NULL, "method ref was unexpectedly cleared");
-
-          // Remove the emcp method if it's not executing
-          // If it's been made obsolete by a redefinition of a non-emcp
-          // method, mark it as obsolete but leave it to clean up later.
+
           if (!method->on_stack()) {
-            method_refs->remove_at(j);
-          } else if (emcp_method_count == 0) {
-            method->set_is_obsolete();
+            // no breakpoints for non-running methods
+            if (method->is_running_emcp()) {
+              method->set_running_emcp(false);
+            }
           } else {
+            assert (method->is_obsolete() || method->is_running_emcp(),
+                    "emcp method cannot run after emcp bit is cleared");
             // RC_TRACE macro has an embedded ResourceMark
             RC_TRACE(0x00000200,
               ("purge: %s(%s): prev method @%d in version @%d is alive",
               method->name()->as_C_string(),
-              method->signature()->as_C_string(), j, i));
+              method->signature()->as_C_string(), j, version));
             if (method->method_data() != NULL) {
-              // Clean out any weak method links
+              // Clean out any weak method links for running methods
+              // (also should include not EMCP methods)
               method->method_data()->clean_weak_method_links();
             }
           }
         }
       }
+      // next previous version
+      last = pv_node;
+      pv_node = pv_node->previous_versions();
+      version++;
     }
-    assert(ik->previous_versions()->length() == live_count, "sanity check");
     RC_TRACE(0x00000200,
       ("purge: previous version stats: live=%d, deleted=%d", live_count,
       deleted_count));
   }
 
+  // Clean MethodData of this class's methods so they don't refer to
+  // old methods that are no longer running.
   Array<Method*>* methods = ik->methods();
   int num_methods = methods->length();
   for (int index2 = 0; index2 < num_methods; ++index2) {
@@ -3540,122 +3531,30 @@
   }
 }
 
-// External interface for use during class unloading.
-void InstanceKlass::purge_previous_versions(InstanceKlass* ik) {
-  // Call with >0 emcp methods since they are not currently being redefined.
-  purge_previous_versions_internal(ik, 1);
-}
-
-
-// Potentially add an information node that contains pointers to the
-// interesting parts of the previous version of the_class.
-// This is also where we clean out any unused references.
-// Note that while we delete nodes from the _previous_versions
-// array, we never delete the array itself until the klass is
-// unloaded. The has_been_redefined() query depends on that fact.
-//
-void InstanceKlass::add_previous_version(instanceKlassHandle ikh,
-       BitMap* emcp_methods, int emcp_method_count) {
-  assert(Thread::current()->is_VM_thread(),
-         "only VMThread can add previous versions");
-
-  if (_previous_versions == NULL) {
-    // This is the first previous version so make some space.
-    // Start with 2 elements under the assumption that the class
-    // won't be redefined much.
-    _previous_versions =  new (ResourceObj::C_HEAP, mtClass)
-                            GrowableArray<PreviousVersionNode *>(2, true);
-  }
-
-  ConstantPool* cp_ref = ikh->constants();
-
-  // RC_TRACE macro has an embedded ResourceMark
-  RC_TRACE(0x00000400, ("adding previous version ref for %s @%d, EMCP_cnt=%d "
-                        "on_stack=%d",
-    ikh->external_name(), _previous_versions->length(), emcp_method_count,
-    cp_ref->on_stack()));
-
-  // If the constant pool for this previous version of the class
-  // is not marked as being on the stack, then none of the methods
-  // in this previous version of the class are on the stack so
-  // we don't need to create a new PreviousVersionNode. However,
-  // we still need to examine older previous versions below.
-  Array<Method*>* old_methods = ikh->methods();
-
-  if (cp_ref->on_stack()) {
-    PreviousVersionNode * pv_node = NULL;
-    if (emcp_method_count == 0) {
-      // non-shared ConstantPool gets a reference
-      pv_node = new PreviousVersionNode(cp_ref, NULL);
-      RC_TRACE(0x00000400,
-          ("add: all methods are obsolete; flushing any EMCP refs"));
-    } else {
-      int local_count = 0;
-      GrowableArray<Method*>* method_refs = new (ResourceObj::C_HEAP, mtClass)
-          GrowableArray<Method*>(emcp_method_count, true);
-      for (int i = 0; i < old_methods->length(); i++) {
-        if (emcp_methods->at(i)) {
-            // this old method is EMCP. Save it only if it's on the stack
-            Method* old_method = old_methods->at(i);
-            if (old_method->on_stack()) {
-              method_refs->append(old_method);
-            }
-          if (++local_count >= emcp_method_count) {
-            // no more EMCP methods so bail out now
-            break;
-          }
-        }
-      }
-      // non-shared ConstantPool gets a reference
-      pv_node = new PreviousVersionNode(cp_ref, method_refs);
-    }
-    // append new previous version.
-    _previous_versions->append(pv_node);
-  }
-
-  // Since the caller is the VMThread and we are at a safepoint, this
-  // is a good time to clear out unused references.
-
-  RC_TRACE(0x00000400, ("add: previous version length=%d",
-    _previous_versions->length()));
-
-  // Purge previous versions not executing on the stack
-  purge_previous_versions_internal(this, emcp_method_count);
-
+void InstanceKlass::mark_newly_obsolete_methods(Array<Method*>* old_methods,
+                                                int emcp_method_count) {
   int obsolete_method_count = old_methods->length() - emcp_method_count;
 
   if (emcp_method_count != 0 && obsolete_method_count != 0 &&
-      _previous_versions->length() > 0) {
+      _previous_versions != NULL) {
     // We have a mix of obsolete and EMCP methods so we have to
     // clear out any matching EMCP method entries the hard way.
     int local_count = 0;
     for (int i = 0; i < old_methods->length(); i++) {
-      if (!emcp_methods->at(i)) {
+      Method* old_method = old_methods->at(i);
+      if (old_method->is_obsolete()) {
         // only obsolete methods are interesting
-        Method* old_method = old_methods->at(i);
         Symbol* m_name = old_method->name();
         Symbol* m_signature = old_method->signature();
 
-        // we might not have added the last entry
-        for (int j = _previous_versions->length() - 1; j >= 0; j--) {
-          // check the previous versions array for non executing obsolete methods
-          PreviousVersionNode * pv_node = _previous_versions->at(j);
-
-          GrowableArray<Method*>* method_refs = pv_node->prev_EMCP_methods();
-          if (method_refs == NULL) {
-            // We have run into a PreviousVersion generation where
-            // all methods were made obsolete during that generation's
-            // RedefineClasses() operation. At the time of that
-            // operation, all EMCP methods were flushed so we don't
-            // have to go back any further.
-            //
-            // A NULL method_refs is different than an empty method_refs.
-            // We cannot infer any optimizations about older generations
-            // from an empty method_refs for the current generation.
-            break;
-          }
-
-          for (int k = method_refs->length() - 1; k >= 0; k--) {
+        // previous versions are linked together through the InstanceKlass
+        int j = 0;
+        for (InstanceKlass* prev_version = _previous_versions;
+             prev_version != NULL;
+             prev_version = prev_version->previous_versions(), j++) {
+
+          Array<Method*>* method_refs = prev_version->methods();
+          for (int k = 0; k < method_refs->length(); k++) {
             Method* method = method_refs->at(k);
 
             if (!method->is_obsolete() &&
@@ -3663,14 +3562,11 @@
                 method->signature() == m_signature) {
               // The current RedefineClasses() call has made all EMCP
               // versions of this method obsolete so mark it as obsolete
-              // and remove the reference.
               RC_TRACE(0x00000400,
                 ("add: %s(%s): flush obsolete method @%d in version @%d",
                 m_name->as_C_string(), m_signature->as_C_string(), k, j));
 
               method->set_is_obsolete();
-              // Leave obsolete methods on the previous version list to
-              // clean up later.
               break;
             }
           }
@@ -3678,9 +3574,9 @@
           // The previous loop may not find a matching EMCP method, but
           // that doesn't mean that we can optimize and not go any
           // further back in the PreviousVersion generations. The EMCP
-          // method for this generation could have already been deleted,
+          // method for this generation could have already been made obsolete,
           // but there still may be an older EMCP method that has not
-          // been deleted.
+          // been made obsolete.
         }
 
         if (++local_count >= obsolete_method_count) {
@@ -3690,15 +3586,69 @@
       }
     }
   }
+}
+
+// Save the scratch_class as the previous version if any of the methods are running.
+// The previous_versions are used to set breakpoints in EMCP methods and they are
+// also used to clean MethodData links to redefined methods that are no longer running.
+void InstanceKlass::add_previous_version(instanceKlassHandle scratch_class,
+                                         int emcp_method_count) {
+  assert(Thread::current()->is_VM_thread(),
+         "only VMThread can add previous versions");
+
+  // RC_TRACE macro has an embedded ResourceMark
+  RC_TRACE(0x00000400, ("adding previous version ref for %s, EMCP_cnt=%d",
+    scratch_class->external_name(), emcp_method_count));
+
+  // Clean out old previous versions
+  purge_previous_versions(this);
+
+  // Mark newly obsolete methods in remaining previous versions.  An EMCP method from
+  // a previous redefinition may be made obsolete by this redefinition.
+  Array<Method*>* old_methods = scratch_class->methods();
+  mark_newly_obsolete_methods(old_methods, emcp_method_count);
+
+  // If the constant pool for this previous version of the class
+  // is not marked as being on the stack, then none of the methods
+  // in this previous version of the class are on the stack so
+  // we don't need to add this as a previous version.
+  ConstantPool* cp_ref = scratch_class->constants();
+  if (!cp_ref->on_stack()) {
+    RC_TRACE(0x00000400, ("add: scratch class not added; no methods are running"));
+    return;
+  }
+
+  if (emcp_method_count != 0) {
+    // At least one method is still running, check for EMCP methods
+    for (int i = 0; i < old_methods->length(); i++) {
+      Method* old_method = old_methods->at(i);
+      if (!old_method->is_obsolete() && old_method->on_stack()) {
+        // if EMCP method (not obsolete) is on the stack, mark as EMCP so that
+        // we can add breakpoints for it.
+
+        // We set the method->on_stack bit during safepoints for class redefinition and
+        // class unloading and use this bit to set the is_running_emcp bit.
+        // After the safepoint, the on_stack bit is cleared and the running emcp
+        // method may exit.   If so, we would set a breakpoint in a method that
+        // is never reached, but this won't be noticeable to the programmer.
+        old_method->set_running_emcp(true);
+        RC_TRACE(0x00000400, ("add: EMCP method %s is on_stack " INTPTR_FORMAT,
+                              old_method->name_and_sig_as_C_string(), old_method));
+      } else if (!old_method->is_obsolete()) {
+        RC_TRACE(0x00000400, ("add: EMCP method %s is NOT on_stack " INTPTR_FORMAT,
+                              old_method->name_and_sig_as_C_string(), old_method));
+      }
+    }
+  }
+
+  // Add previous version if any methods are still running.
+  RC_TRACE(0x00000400, ("add: scratch class added; one of its methods is on_stack"));
+  assert(scratch_class->previous_versions() == NULL, "shouldn't have a previous version");
+  scratch_class->link_previous_versions(previous_versions());
+  link_previous_versions(scratch_class());
 } // end add_previous_version()
 
 
-// Determine if InstanceKlass has a previous version.
-bool InstanceKlass::has_previous_version() const {
-  return (_previous_versions != NULL && _previous_versions->length() > 0);
-} // end has_previous_version()
-
-
 Method* InstanceKlass::method_with_idnum(int idnum) {
   Method* m = NULL;
   if (idnum < methods()->length()) {
@@ -3724,61 +3674,3 @@
 unsigned char * InstanceKlass::get_cached_class_file_bytes() {
   return VM_RedefineClasses::get_cached_class_file_bytes(_cached_class_file);
 }
-
-
-// Construct a PreviousVersionNode entry for the array hung off
-// the InstanceKlass.
-PreviousVersionNode::PreviousVersionNode(ConstantPool* prev_constant_pool,
-  GrowableArray<Method*>* prev_EMCP_methods) {
-
-  _prev_constant_pool = prev_constant_pool;
-  _prev_EMCP_methods = prev_EMCP_methods;
-}
-
-
-// Destroy a PreviousVersionNode
-PreviousVersionNode::~PreviousVersionNode() {
-  if (_prev_constant_pool != NULL) {
-    _prev_constant_pool = NULL;
-  }
-
-  if (_prev_EMCP_methods != NULL) {
-    delete _prev_EMCP_methods;
-  }
-}
-
-// Construct a helper for walking the previous versions array
-PreviousVersionWalker::PreviousVersionWalker(Thread* thread, InstanceKlass *ik) {
-  _thread = thread;
-  _previous_versions = ik->previous_versions();
-  _current_index = 0;
-  _current_p = NULL;
-  _current_constant_pool_handle = constantPoolHandle(thread, ik->constants());
-}
-
-
-// Return the interesting information for the next previous version
-// of the klass. Returns NULL if there are no more previous versions.
-PreviousVersionNode* PreviousVersionWalker::next_previous_version() {
-  if (_previous_versions == NULL) {
-    // no previous versions so nothing to return
-    return NULL;
-  }
-
-  _current_p = NULL;  // reset to NULL
-  _current_constant_pool_handle = NULL;
-
-  int length = _previous_versions->length();
-
-  while (_current_index < length) {
-    PreviousVersionNode * pv_node = _previous_versions->at(_current_index++);
-
-    // Save a handle to the constant pool for this previous version,
-    // which keeps all the methods from being deallocated.
-    _current_constant_pool_handle = constantPoolHandle(_thread, pv_node->prev_constant_pool());
-    _current_p = pv_node;
-    return pv_node;
-  }
-
-  return NULL;
-} // end next_previous_version()

--- a/hotspot/src/share/vm/oops/instanceKlass.hpp	Wed Sep 03 14:43:49 2014 +0200
+++ b/hotspot/src/share/vm/oops/instanceKlass.hpp	Wed Sep 03 19:13:18 2014 -0400
@@ -59,7 +59,6 @@
 class fieldDescriptor;
 class DepChange;
 class nmethodBucket;
-class PreviousVersionNode;
 class JvmtiCachedClassFieldMap;
 class MemberNameTable;
 
@@ -205,7 +204,8 @@
     _misc_should_verify_class  = 1 << 2, // allow caching of preverification
     _misc_is_anonymous         = 1 << 3, // has embedded _host_klass field
     _misc_is_contended         = 1 << 4, // marked with contended annotation
-    _misc_has_default_methods  = 1 << 5  // class/superclass/implemented interfaces has default methods
+    _misc_has_default_methods  = 1 << 5, // class/superclass/implemented interfaces has default methods
+    _misc_has_been_redefined   = 1 << 6  // class has been redefined
   };
   u2              _misc_flags;
   u2              _minor_version;        // minor version number of class file
@@ -220,9 +220,8 @@
   nmethodBucket*  _dependencies;         // list of dependent nmethods
   nmethod*        _osr_nmethods_head;    // Head of list of on-stack replacement nmethods for this class
   BreakpointInfo* _breakpoints;          // bpt lists, managed by Method*
-  // Array of interesting part(s) of the previous version(s) of this
-  // InstanceKlass. See PreviousVersionWalker below.
-  GrowableArray<PreviousVersionNode *>* _previous_versions;
+  // Linked instanceKlasses of previous versions
+  InstanceKlass* _previous_versions;
   // JVMTI fields can be moved to their own structure - see 6315920
   // JVMTI: cached class file, before retransformable agent modified it in CFLH
   JvmtiCachedClassFileData* _cached_class_file;
@@ -608,19 +607,20 @@
   }
 
   // RedefineClasses() support for previous versions:
-  void add_previous_version(instanceKlassHandle ikh, BitMap *emcp_methods,
-         int emcp_method_count);
-  // If the _previous_versions array is non-NULL, then this klass
-  // has been redefined at least once even if we aren't currently
-  // tracking a previous version.
-  bool has_been_redefined() const { return _previous_versions != NULL; }
-  bool has_previous_version() const;
+  void add_previous_version(instanceKlassHandle ikh, int emcp_method_count);
+
+  InstanceKlass* previous_versions() const { return _previous_versions; }
+
+  bool has_been_redefined() const {
+    return (_misc_flags & _misc_has_been_redefined) != 0;
+  }
+  void set_has_been_redefined() {
+    _misc_flags |= _misc_has_been_redefined;
+  }
+
   void init_previous_versions() {
     _previous_versions = NULL;
   }
-  GrowableArray<PreviousVersionNode *>* previous_versions() const {
-    return _previous_versions;
-  }
 
   static void purge_previous_versions(InstanceKlass* ik);
 
@@ -1042,6 +1042,10 @@
 
   // Free CHeap allocated fields.
   void release_C_heap_structures();
+
+  // RedefineClasses support
+  void link_previous_versions(InstanceKlass* pv) { _previous_versions = pv; }
+  void mark_newly_obsolete_methods(Array<Method*>* old_methods, int emcp_method_count);
 public:
   // CDS support - remove and restore oops from metadata. Oops are not shared.
   virtual void remove_unshareable_info();
@@ -1141,62 +1145,6 @@
 };
 
 
-// If breakpoints are more numerous than just JVMTI breakpoints,
-// consider compressing this data structure.
-// It is currently a simple linked list defined in method.hpp.
-
-class BreakpointInfo;
-
-
-// A collection point for interesting information about the previous
-// version(s) of an InstanceKlass.  A GrowableArray of PreviousVersionNodes
-// is attached to the InstanceKlass as needed. See PreviousVersionWalker below.
-class PreviousVersionNode : public CHeapObj<mtClass> {
- private:
-  ConstantPool*    _prev_constant_pool;
-
-  // If the previous version of the InstanceKlass doesn't have any
-  // EMCP methods, then _prev_EMCP_methods will be NULL. If all the
-  // EMCP methods have been collected, then _prev_EMCP_methods can
-  // have a length of zero.
-  GrowableArray<Method*>* _prev_EMCP_methods;
-
-public:
-  PreviousVersionNode(ConstantPool* prev_constant_pool,
-                      GrowableArray<Method*>* prev_EMCP_methods);
-  ~PreviousVersionNode();
-  ConstantPool* prev_constant_pool() const {
-    return _prev_constant_pool;
-  }
-  GrowableArray<Method*>* prev_EMCP_methods() const {
-    return _prev_EMCP_methods;
-  }
-};
-
-
-// Helper object for walking previous versions.
-class PreviousVersionWalker : public StackObj {
- private:
-  Thread*                               _thread;
-  GrowableArray<PreviousVersionNode *>* _previous_versions;
-  int                                   _current_index;
-
-  // A pointer to the current node object so we can handle the deletes.
-  PreviousVersionNode*                  _current_p;
-
-  // The constant pool handle keeps all the methods in this class from being
-  // deallocated from the metaspace during class unloading.
-  constantPoolHandle                    _current_constant_pool_handle;
-
- public:
-  PreviousVersionWalker(Thread* thread, InstanceKlass *ik);
-
-  // Return the interesting information for the next previous version
-  // of the klass. Returns NULL if there are no more previous versions.
-  PreviousVersionNode* next_previous_version();
-};
-
-
 //
 // nmethodBucket is used to record dependent nmethods for
 // deoptimization.  nmethod dependencies are actually <klass, method>

--- a/hotspot/src/share/vm/oops/method.hpp	Wed Sep 03 14:43:49 2014 +0200
+++ b/hotspot/src/share/vm/oops/method.hpp	Wed Sep 03 19:13:18 2014 -0400
@@ -80,7 +80,8 @@
     _caller_sensitive = 1 << 1,
     _force_inline     = 1 << 2,
     _dont_inline      = 1 << 3,
-    _hidden           = 1 << 4
+    _hidden           = 1 << 4,
+    _running_emcp     = 1 << 5
   };
   u1 _flags;
 
@@ -688,6 +689,21 @@
   void set_is_obsolete()                            { _access_flags.set_is_obsolete(); }
   bool is_deleted() const                           { return access_flags().is_deleted(); }
   void set_is_deleted()                             { _access_flags.set_is_deleted(); }
+
+  bool is_running_emcp() const {
+    // EMCP methods are old but not obsolete or deleted. Equivalent
+    // Modulo Constant Pool means the method is equivalent except
+    // the constant pool and instructions that access the constant
+    // pool might be different.
+    // If a breakpoint is set in a redefined method, its EMCP methods that are
+    // still running must have a breakpoint also.
+    return (_flags & _running_emcp) != 0;
+  }
+
+  void set_running_emcp(bool x) {
+    _flags = x ? (_flags | _running_emcp) : (_flags & ~_running_emcp);
+  }
+
   bool on_stack() const                             { return access_flags().on_stack(); }
   void set_on_stack(const bool value);
 

--- a/hotspot/src/share/vm/prims/jvmtiImpl.cpp	Wed Sep 03 14:43:49 2014 +0200
+++ b/hotspot/src/share/vm/prims/jvmtiImpl.cpp	Wed Sep 03 19:13:18 2014 -0400
@@ -282,39 +282,22 @@
 void JvmtiBreakpoint::each_method_version_do(method_action meth_act) {
   ((Method*)_method->*meth_act)(_bci);
 
-  // add/remove breakpoint to/from versions of the method that
-  // are EMCP. Directly or transitively obsolete methods are
-  // not saved in the PreviousVersionNodes.
+  // add/remove breakpoint to/from versions of the method that are EMCP.
   Thread *thread = Thread::current();
   instanceKlassHandle ikh = instanceKlassHandle(thread, _method->method_holder());
   Symbol* m_name = _method->name();
   Symbol* m_signature = _method->signature();
 
   // search previous versions if they exist
-  PreviousVersionWalker pvw(thread, (InstanceKlass *)ikh());
-  for (PreviousVersionNode * pv_node = pvw.next_previous_version();
-       pv_node != NULL; pv_node = pvw.next_previous_version()) {
-    GrowableArray<Method*>* methods = pv_node->prev_EMCP_methods();
-
-    if (methods == NULL) {
-      // We have run into a PreviousVersion generation where
-      // all methods were made obsolete during that generation's
-      // RedefineClasses() operation. At the time of that
-      // operation, all EMCP methods were flushed so we don't
-      // have to go back any further.
-      //
-      // A NULL methods array is different than an empty methods
-      // array. We cannot infer any optimizations about older
-      // generations from an empty methods array for the current
-      // generation.
-      break;
-    }
+  for (InstanceKlass* pv_node = ikh->previous_versions();
+       pv_node != NULL;
+       pv_node = pv_node->previous_versions()) {
+    Array<Method*>* methods = pv_node->methods();
 
     for (int i = methods->length() - 1; i >= 0; i--) {
       Method* method = methods->at(i);
-      // obsolete methods that are running are not deleted from
-      // previous version array, but they are skipped here.
-      if (!method->is_obsolete() &&
+      // Only set breakpoints in running EMCP methods.
+      if (method->is_running_emcp() &&
           method->name() == m_name &&
           method->signature() == m_signature) {
         RC_TRACE(0x00000800, ("%sing breakpoint in %s(%s)",

--- a/hotspot/src/share/vm/prims/jvmtiRedefineClasses.cpp	Wed Sep 03 14:43:49 2014 +0200
+++ b/hotspot/src/share/vm/prims/jvmtiRedefineClasses.cpp	Wed Sep 03 19:13:18 2014 -0400
@@ -135,7 +135,7 @@
 
   // Mark methods seen on stack and everywhere else so old methods are not
   // cleaned up if they're on the stack.
-  MetadataOnStackMark md_on_stack;
+  MetadataOnStackMark md_on_stack(true);
   HandleMark hm(thread);   // make sure any handles created are deleted
                            // before the stack walk again.
 
@@ -2826,11 +2826,10 @@
     }
 
     // the previous versions' constant pool caches may need adjustment
-    PreviousVersionWalker pvw(_thread, ik);
-    for (PreviousVersionNode * pv_node = pvw.next_previous_version();
-         pv_node != NULL; pv_node = pvw.next_previous_version()) {
-      other_cp = pv_node->prev_constant_pool();
-      cp_cache = other_cp->cache();
+    for (InstanceKlass* pv_node = ik->previous_versions();
+         pv_node != NULL;
+         pv_node = pv_node->previous_versions()) {
+      cp_cache = pv_node->constants()->cache();
       if (cp_cache != NULL) {
         cp_cache->adjust_method_entries(_matching_old_methods,
                                         _matching_new_methods,
@@ -2855,9 +2854,8 @@
   }
 }
 
-void VM_RedefineClasses::check_methods_and_mark_as_obsolete(
-       BitMap *emcp_methods, int * emcp_method_count_p) {
-  *emcp_method_count_p = 0;
+int VM_RedefineClasses::check_methods_and_mark_as_obsolete() {
+  int emcp_method_count = 0;
   int obsolete_count = 0;
   int old_index = 0;
   for (int j = 0; j < _matching_methods_length; ++j, ++old_index) {
@@ -2931,9 +2929,9 @@
       // that we get from effectively overwriting the old methods
       // when the new methods are attached to the_class.
 
-      // track which methods are EMCP for add_previous_version() call
-      emcp_methods->set_bit(old_index);
-      (*emcp_method_count_p)++;
+      // Count number of methods that are EMCP.  The method will be marked
+      // old but not obsolete if it is EMCP.
+      emcp_method_count++;
 
       // An EMCP method is _not_ obsolete. An obsolete method has a
       // different jmethodID than the current method. An EMCP method
@@ -2982,10 +2980,11 @@
                           old_method->name()->as_C_string(),
                           old_method->signature()->as_C_string()));
   }
-  assert((*emcp_method_count_p + obsolete_count) == _old_methods->length(),
+  assert((emcp_method_count + obsolete_count) == _old_methods->length(),
     "sanity check");
-  RC_TRACE(0x00000100, ("EMCP_cnt=%d, obsolete_cnt=%d", *emcp_method_count_p,
+  RC_TRACE(0x00000100, ("EMCP_cnt=%d, obsolete_cnt=%d", emcp_method_count,
     obsolete_count));
+  return emcp_method_count;
 }
 
 // This internal class transfers the native function registration from old methods
@@ -3379,11 +3378,8 @@
   old_constants->set_pool_holder(scratch_class());
 #endif
 
-  // track which methods are EMCP for add_previous_version() call below
-  BitMap emcp_methods(_old_methods->length());
-  int emcp_method_count = 0;
-  emcp_methods.clear();  // clears 0..(length() - 1)
-  check_methods_and_mark_as_obsolete(&emcp_methods, &emcp_method_count);
+  // track number of methods that are EMCP for add_previous_version() call below
+  int emcp_method_count = check_methods_and_mark_as_obsolete();
   transfer_old_native_function_registrations(the_class);
 
   // The class file bytes from before any retransformable agents mucked
@@ -3471,9 +3467,10 @@
     scratch_class->enclosing_method_method_index());
   scratch_class->set_enclosing_method_indices(old_class_idx, old_method_idx);
 
+  the_class->set_has_been_redefined();
+
   // keep track of previous versions of this class
-  the_class->add_previous_version(scratch_class, &emcp_methods,
-    emcp_method_count);
+  the_class->add_previous_version(scratch_class, emcp_method_count);
 
   RC_TIMER_STOP(_timer_rsc_phase1);
   RC_TIMER_START(_timer_rsc_phase2);

--- a/hotspot/src/share/vm/prims/jvmtiRedefineClasses.hpp	Wed Sep 03 14:43:49 2014 +0200
+++ b/hotspot/src/share/vm/prims/jvmtiRedefineClasses.hpp	Wed Sep 03 19:13:18 2014 -0400
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2014, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -403,14 +403,9 @@
   // Change jmethodIDs to point to the new methods
   void update_jmethod_ids();
 
-  // In addition to marking methods as obsolete, this routine
-  // records which methods are EMCP (Equivalent Module Constant
-  // Pool) in the emcp_methods BitMap and returns the number of
-  // EMCP methods via emcp_method_count_p. This information is
-  // used when information about the previous version of the_class
-  // is squirreled away.
-  void check_methods_and_mark_as_obsolete(BitMap *emcp_methods,
-         int * emcp_method_count_p);
+  // In addition to marking methods as old and/or obsolete, this routine
+  // counts the number of methods that are EMCP (Equivalent Module Constant Pool).
+  int check_methods_and_mark_as_obsolete();
   void transfer_old_native_function_registrations(instanceKlassHandle the_class);
 
   // Install the redefinition of a class

--- a/hotspot/test/runtime/RedefineFinalizer/RedefineFinalizer.java	Wed Sep 03 14:43:49 2014 +0200
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,64 +0,0 @@
-/*
- * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
- * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
- *
- * This code is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License version 2 only, as
- * published by the Free Software Foundation.
- *
- * This code is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
- * version 2 for more details (a copy is included in the LICENSE file that
- * accompanied this code).
- *
- * You should have received a copy of the GNU General Public License version
- * 2 along with this work; if not, write to the Free Software Foundation,
- * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
- *
- * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
- * or visit www.oracle.com if you need additional information or have any
- * questions.
- */
-
-/*
- * @test
- * @bug 6904403
- * @summary Don't assert if we redefine finalize method
- * @library /testlibrary
- * @build RedefineClassHelper
- * @run main RedefineClassHelper
- * @run main/othervm -javaagent:redefineagent.jar RedefineFinalizer
- */
-
-/*
- * Regression test for hitting:
- *
- * assert(f == k->has_finalizer()) failed: inconsistent has_finalizer
- *
- * when redefining finalizer method
- */
-public class RedefineFinalizer {
-
-    public static String newB =
-                "class RedefineFinalizer$B {" +
-                "   protected void finalize() { " +
-                "       System.out.println(\"Finalizer called\");" +
-                "   }" +
-                "}";
-
-    public static void main(String[] args) throws Exception {
-        RedefineClassHelper.redefineClass(B.class, newB);
-
-        A a = new A();
-    }
-
-    static class A extends B {
-    }
-
-    static class B {
-        protected void finalize() {
-            // should be empty
-        }
-    }
-}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/test/runtime/RedefineTests/RedefineFinalizer.java	Wed Sep 03 19:13:18 2014 -0400
@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 6904403
+ * @summary Don't assert if we redefine finalize method
+ * @library /testlibrary
+ * @build RedefineClassHelper
+ * @run main RedefineClassHelper
+ * @run main/othervm -javaagent:redefineagent.jar RedefineFinalizer
+ */
+
+/*
+ * Regression test for hitting:
+ *
+ * assert(f == k->has_finalizer()) failed: inconsistent has_finalizer
+ *
+ * when redefining finalizer method
+ */
+public class RedefineFinalizer {
+
+    public static String newB =
+                "class RedefineFinalizer$B {" +
+                "   protected void finalize() { " +
+                "       System.out.println(\"Finalizer called\");" +
+                "   }" +
+                "}";
+
+    public static void main(String[] args) throws Exception {
+        RedefineClassHelper.redefineClass(B.class, newB);
+
+        A a = new A();
+    }
+
+    static class A extends B {
+    }
+
+    static class B {
+        protected void finalize() {
+            // should be empty
+        }
+    }
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/test/runtime/RedefineTests/RedefineRunningMethods.java	Wed Sep 03 19:13:18 2014 -0400
@@ -0,0 +1,143 @@
+/*
+ * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 8055008
+ * @summary Redefine EMCP and non-EMCP methods that are running in an infinite loop
+ * @library /testlibrary
+ * @build RedefineClassHelper
+ * @run main RedefineClassHelper
+ * @run main/othervm -javaagent:redefineagent.jar -XX:TraceRedefineClasses=0x600 RedefineRunningMethods
+ */
+public class RedefineRunningMethods {
+
+    public static String newB =
+                "class RedefineRunningMethods$B {" +
+                "   static int count1 = 0;" +
+                "   static int count2 = 0;" +
+                "   public static volatile boolean stop = false;" +
+                "  static void localSleep() { " +
+                "    try{ " +
+                "      Thread.currentThread().sleep(10);" +
+                "    } catch(InterruptedException ie) { " +
+                "    } " +
+                " } " +
+                "   public static void infinite() { " +
+                "       System.out.println(\"infinite called\");" +
+                "   }" +
+                "   public static void infinite_emcp() { " +
+                "       while (!stop) { count2++; localSleep(); }" +
+                "   }" +
+                "}";
+
+    public static String evenNewerB =
+                "class RedefineRunningMethods$B {" +
+                "   static int count1 = 0;" +
+                "   static int count2 = 0;" +
+                "   public static volatile boolean stop = false;" +
+                "  static void localSleep() { " +
+                "    try{ " +
+                "      Thread.currentThread().sleep(1);" +
+                "    } catch(InterruptedException ie) { " +
+                "    } " +
+                " } " +
+                "   public static void infinite() { }" +
+                "   public static void infinite_emcp() { " +
+                "       System.out.println(\"infinite_emcp now obsolete called\");" +
+                "   }" +
+                "}";
+
+    static class B {
+        static int count1 = 0;
+        static int count2 = 0;
+        public static volatile boolean stop = false;
+        static void localSleep() {
+          try{
+            Thread.currentThread().sleep(10);//sleep for 10 ms
+          } catch(InterruptedException ie) {
+          }
+        }
+
+        public static void infinite() {
+            while (!stop) { count1++; localSleep(); }
+        }
+        public static void infinite_emcp() {
+            while (!stop) { count2++; localSleep(); }
+        }
+    }
+
+
+    public static void main(String[] args) throws Exception {
+
+        new Thread() {
+            public void run() {
+                B.infinite();
+            }
+        }.start();
+
+        new Thread() {
+            public void run() {
+                B.infinite_emcp();
+            }
+        }.start();
+
+        RedefineClassHelper.redefineClass(B.class, newB);
+
+        System.gc();
+
+        B.infinite();
+
+        // Start a thread with the second version of infinite_emcp running
+        new Thread() {
+            public void run() {
+                B.infinite_emcp();
+            }
+        }.start();
+
+        for (int i = 0; i < 20 ; i++) {
+            String s = new String("some garbage");
+            System.gc();
+        }
+
+        RedefineClassHelper.redefineClass(B.class, evenNewerB);
+        System.gc();
+
+        for (int i = 0; i < 20 ; i++) {
+            B.infinite();
+            String s = new String("some garbage");
+            System.gc();
+        }
+
+        B.infinite_emcp();
+
+        // purge should clean everything up.
+        B.stop = true;
+
+        for (int i = 0; i < 20 ; i++) {
+            B.infinite();
+            String s = new String("some garbage");
+            System.gc();
+        }
+    }
+}