src/hotspot/share/gc/g1/g1FreeIdSet.cpp

rev 53151 : [mq]: tschatzl_review

*** 28,39 ****
  #include "runtime/atomic.hpp"
  #include "utilities/debug.hpp"
  #include "utilities/globalDefinitions.hpp"
  #include "utilities/macros.hpp"
  
- const uint claimed = UINT_MAX;
- 
  G1FreeIdSet::G1FreeIdSet(uint start, uint size) :
    _sem(size),          // counting semaphore for available ids
    _next(NULL),         // array of "next" indices
    _start(start),       // first id value
    _size(size),         // number of available ids
--- 28,37 ----
*** 66,75 ****
--- 64,75 ----
  uintx G1FreeIdSet::make_head(uint index, uintx old_head) const {
    // Include incremented old update counter to avoid ABA problem.
    return index | ((old_head & ~_head_index_mask) + 1 + _head_index_mask);
  }
  
+ const uint Claimed = UINT_MAX;
+ 
  uint G1FreeIdSet::claim_par_id() {
    _sem.wait();
    // Semaphore gate permits passage by no more than the number of
    // available ids, so there must be one that we can claim.  But there
    // may be multiple threads trying to claim ids at the same time.
*** 81,98 ****
      uintx new_head = make_head(_next[index], old_head);
      new_head = Atomic::cmpxchg(new_head, &_head, old_head);
      if (new_head == old_head) break;
      old_head = new_head;
    }
!   DEBUG_ONLY(_next[index] = claimed;)
    return _start + index;
  }
  
  void G1FreeIdSet::release_par_id(uint id) {
    uint index = id - _start;
    assert(index < _size, "invalid id %u", id);
!   assert(_next[index] == claimed, "precondition");
    uintx old_head = Atomic::load(&_head);
    while (true) {
      _next[index] = head_index(old_head);
      uintx new_head = make_head(index, old_head);
      new_head = Atomic::cmpxchg(new_head, &_head, old_head);
--- 81,98 ----
      uintx new_head = make_head(_next[index], old_head);
      new_head = Atomic::cmpxchg(new_head, &_head, old_head);
      if (new_head == old_head) break;
      old_head = new_head;
    }
!   DEBUG_ONLY(_next[index] = Claimed;)
    return _start + index;
  }
  
  void G1FreeIdSet::release_par_id(uint id) {
    uint index = id - _start;
    assert(index < _size, "invalid id %u", id);
!   assert(_next[index] == Claimed, "precondition");
    uintx old_head = Atomic::load(&_head);
    while (true) {
      _next[index] = head_index(old_head);
      uintx new_head = make_head(index, old_head);
      new_head = Atomic::cmpxchg(new_head, &_head, old_head);