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hotspot/src/share/vm/gc_implementation/g1/satbQueue.hpp

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rev 7368 : 8075215: SATB buffer processing found reclaimed humongous object
Summary: Don't assume SATB buffer entries are valid objects
Reviewed-by: brutisso, ecaspole

@@ -1,7 +1,7 @@
 /*
- * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2015, 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.

@@ -23,36 +23,34 @@
  */
 
 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_SATBQUEUE_HPP
 #define SHARE_VM_GC_IMPLEMENTATION_G1_SATBQUEUE_HPP
 
+#include "memory/allocation.hpp"
 #include "gc_implementation/g1/ptrQueue.hpp"
 
-class ObjectClosure;
 class JavaThread;
 class SATBMarkQueueSet;
 
+// Base class for processing the contents of a SATB buffer.
+class SATBBufferClosure : public StackObj {
+protected:
+  ~SATBBufferClosure() { }
+
+public:
+  // Process the SATB entries in the designated buffer range.
+  virtual void do_buffer(void** buffer, size_t size) = 0;
+};
+
 // A ptrQueue whose elements are "oops", pointers to object heads.
 class ObjPtrQueue: public PtrQueue {
-  friend class Threads;
   friend class SATBMarkQueueSet;
-  friend class G1RemarkThreadsClosure;
 
 private:
   // Filter out unwanted entries from the buffer.
   void filter();
 
-  // Apply the closure to all elements.
-  void apply_closure(ObjectClosure* cl);
-
-  // Apply the closure to all elements and empty the buffer;
-  void apply_closure_and_empty(ObjectClosure* cl);
-
-  // Apply the closure to all elements of "buf", down to "index" (inclusive.)
-  static void apply_closure_to_buffer(ObjectClosure* cl,
-                                      void** buf, size_t index, size_t sz);
-
 public:
   ObjPtrQueue(PtrQueueSet* qset, bool perm = false) :
     // SATB queues are only active during marking cycles. We create
     // them with their active field set to false. If a thread is
     // created during a cycle and its SATB queue needs to be activated

@@ -61,34 +59,28 @@
     PtrQueue(qset, perm, false /* active */) { }
 
   // Process queue entries and free resources.
   void flush();
 
+  // Apply cl to the active part of the buffer.
+  // Prerequisite: Must be at a safepoint.
+  void apply_closure_and_empty(SATBBufferClosure* cl);
+
   // Overrides PtrQueue::should_enqueue_buffer(). See the method's
   // definition for more information.
   virtual bool should_enqueue_buffer();
 
 #ifndef PRODUCT
   // Helpful for debugging
   void print(const char* name);
   static void print(const char* name, void** buf, size_t index, size_t sz);
 #endif // PRODUCT
-
-  void verify_oops_in_buffer() NOT_DEBUG_RETURN;
 };
 
 class SATBMarkQueueSet: public PtrQueueSet {
-  ObjectClosure* _closure;
-  ObjectClosure** _par_closures;  // One per ParGCThread.
-
   ObjPtrQueue _shared_satb_queue;
 
-  // Utility function to support sequential and parallel versions.  If
-  // "par" is true, then "worker" is the par thread id; if "false", worker
-  // is ignored.
-  bool apply_closure_to_completed_buffer_work(bool par, uint worker);
-
 #ifdef ASSERT
   void dump_active_states(bool expected_active);
   void verify_active_states(bool expected_active);
 #endif // ASSERT
 

@@ -108,36 +100,16 @@
   void set_active_all_threads(bool active, bool expected_active);
 
   // Filter all the currently-active SATB buffers.
   void filter_thread_buffers();
 
-  // Register "blk" as "the closure" for all queues.  Only one such closure
-  // is allowed.  The "apply_closure_to_completed_buffer" method will apply
-  // this closure to a completed buffer, and "iterate_closure_all_threads"
-  // applies it to partially-filled buffers (the latter should only be done
-  // with the world stopped).
-  void set_closure(ObjectClosure* closure);
-  // Set the parallel closures: pointer is an array of pointers to
-  // closures, one for each parallel GC thread.
-  void set_par_closure(int i, ObjectClosure* closure);
-
-  // If there exists some completed buffer, pop it, then apply the
-  // registered closure to all its elements, and return true.  If no
-  // completed buffers exist, return false.
-  bool apply_closure_to_completed_buffer() {
-    return apply_closure_to_completed_buffer_work(false, 0);
-  }
-  // Parallel version of the above.
-  bool par_apply_closure_to_completed_buffer(uint worker) {
-    return apply_closure_to_completed_buffer_work(true, worker);
-  }
-
-  // Apply the given closure on enqueued and currently-active buffers
-  // respectively. Both methods are read-only, i.e., they do not
-  // modify any of the buffers.
-  void iterate_completed_buffers_read_only(ObjectClosure* cl);
-  void iterate_thread_buffers_read_only(ObjectClosure* cl);
+  // If there exists some completed buffer, pop and process it, and
+  // return true.  Otherwise return false.  Processing a buffer
+  // consists of applying the closure to the buffer range starting
+  // with the first non-NULL entry to the end of the buffer; the
+  // leading entries may be NULL due to filtering.
+  bool apply_closure_to_completed_buffer(SATBBufferClosure* cl);
 
 #ifndef PRODUCT
   // Helpful for debugging
   void print_all(const char* msg);
 #endif // PRODUCT
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