hotspot/src/share/vm/gc_implementation/g1/satbQueue.hpp
author tonyp
Fri, 01 Oct 2010 16:43:05 -0400
changeset 6768 71338ecb7813
parent 5547 f4b087cbb361
child 7397 5b173b4ca846
permissions -rw-r--r--
6980838: G1: guarantee(false) failed: thread has an unexpected active value in its SATB queue Summary: Under certain circumstances a safepoint could happen between a JavaThread object being created and that object being added to the Java threads list. This could cause the active field of that thread's SATB queue to get out-of-sync with respect to the other Java threads. The solution is to activate the SATB queue, when necessary, before adding the thread to the Java threads list, not when the JavaThread object is created. The changeset also includes a small fix to rename the surrogate locker thread from "Surrogate Locker Thread (CMS)" to "Surrogate Locker Thread (Concurrent GC)" since it's also used in G1. Reviewed-by: iveresov, ysr, johnc, jcoomes

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class ObjectClosure;
class JavaThread;

// A ptrQueue whose elements are "oops", pointers to object heads.
class ObjPtrQueue: public PtrQueue {
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
    // before the thread starts running, we'll need to set its active
    // field to true. This is done in JavaThread::initialize_queues().
    PtrQueue(qset_, perm, false /* active */) { }
  // Apply the closure to all elements, and reset the index to make the
  // buffer empty.
  void apply_closure(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);

  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, int worker);

#ifdef ASSERT
  void dump_active_values(JavaThread* first, bool expected_active);
#endif // ASSERT

public:
  SATBMarkQueueSet();

  void initialize(Monitor* cbl_mon, Mutex* fl_lock,
                  int process_completed_threshold,
                  Mutex* lock);

  static void handle_zero_index_for_thread(JavaThread* t);

  // Apply "set_active(b)" to all Java threads' SATB queues. It should be
  // called only with the world stopped. The method will assert that the
  // SATB queues of all threads it visits, as well as the SATB queue
  // set itself, has an active value same as expected_active.
  void set_active_all_threads(bool b, bool expected_active);

  // 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 is a registered closure for buffers, apply it to all entries
  // in all currently-active buffers.  This should only be applied at a
  // safepoint.  (Currently must not be called in parallel; this should
  // change in the future.)
  void iterate_closure_all_threads();
  // Parallel version of the above.
  void par_iterate_closure_all_threads(int worker);

  // 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(int worker) {
    return apply_closure_to_completed_buffer_work(true, worker);
  }

  ObjPtrQueue* shared_satb_queue() { return &_shared_satb_queue; }

  // If a marking is being abandoned, reset any unprocessed log buffers.
  void abandon_partial_marking();

};