--- old/src/share/vm/gc/g1/dirtyCardQueue.cpp	2015-11-11 14:22:30.165348026 -0500
+++ new/src/share/vm/gc/g1/dirtyCardQueue.cpp	2015-11-11 14:22:28.837272995 -0500
@@ -112,7 +112,7 @@
                           fl_owner);
   set_buffer_size(G1UpdateBufferSize);
   _shared_dirty_card_queue.set_lock(lock);
-  _free_ids = new FreeIdSet((int) num_par_ids(), _cbl_mon);
+  _free_ids = new FreeIdSet(num_par_ids(), _cbl_mon);
 }
 
 void DirtyCardQueueSet::handle_zero_index_for_thread(JavaThread* t) {
--- old/src/share/vm/gc/shared/workgroup.cpp	2015-11-11 14:22:34.257579219 -0500
+++ new/src/share/vm/gc/shared/workgroup.cpp	2015-11-11 14:22:32.933504414 -0500
@@ -505,11 +505,12 @@
 FreeIdSet* FreeIdSet::_sets[NSets];
 bool FreeIdSet::_safepoint;
 
-FreeIdSet::FreeIdSet(int sz, Monitor* mon) :
+FreeIdSet::FreeIdSet(uint sz, Monitor* mon) :
   _sz(sz), _mon(mon), _hd(0), _waiters(0), _index(-1), _claimed(0)
 {
-  _ids = NEW_C_HEAP_ARRAY(int, sz, mtInternal);
-  for (int i = 0; i < sz; i++) _ids[i] = i+1;
+  guarantee(sz != 0, "must be");
+  _ids = NEW_C_HEAP_ARRAY(uint, sz, mtInternal);
+  for (uint i = 0; i < sz - 1; i++) _ids[i] = i+1;
   _ids[sz-1] = end_of_list; // end of list.
   if (_stat_init) {
     for (int j = 0; j < NSets; j++) _sets[j] = NULL;
@@ -528,7 +529,7 @@
 
 FreeIdSet::~FreeIdSet() {
   _sets[_index] = NULL;
-  FREE_C_HEAP_ARRAY(int, _ids);
+  FREE_C_HEAP_ARRAY(uint, _ids);
 }
 
 void FreeIdSet::set_safepoint(bool b) {
@@ -550,7 +551,7 @@
 int FreeIdSet::claim_par_id() {
 #if FID_STATS
   thread_t tslf = thr_self();
-  tty->print("claim_par_id[%d]: sz = %d, claimed = %d\n", tslf, _sz, _claimed);
+  tty->print("claim_par_id[%d]: sz = %u, claimed = %u\n", tslf, _sz, _claimed);
 #endif
   MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);
   while (!_safepoint && _hd == end_of_list) {
@@ -568,52 +569,28 @@
 #if FID_STATS
     tty->print("claim_par_id[%d]: returning EOL.\n", tslf);
 #endif
-    return -1;
+    return UINT_MAX;
   } else {
     int res = _hd;
     _hd = _ids[res];
     _ids[res] = claimed;  // For debugging.
     _claimed++;
 #if FID_STATS
-    tty->print("claim_par_id[%d]: returning %d, claimed = %d.\n",
+    tty->print("claim_par_id[%d]: returning %d, claimed = %u.\n",
                tslf, res, _claimed);
 #endif
     return res;
   }
 }
 
-bool FreeIdSet::claim_perm_id(int i) {
-  assert(0 <= i && i < _sz, "Out of range.");
-  MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);
-  int prev = end_of_list;
-  int cur = _hd;
-  while (cur != end_of_list) {
-    if (cur == i) {
-      if (prev == end_of_list) {
-        _hd = _ids[cur];
-      } else {
-        _ids[prev] = _ids[cur];
-      }
-      _ids[cur] = claimed;
-      _claimed++;
-      return true;
-    } else {
-      prev = cur;
-      cur = _ids[cur];
-    }
-  }
-  return false;
-
-}
-
-void FreeIdSet::release_par_id(int id) {
+void FreeIdSet::release_par_id(uint id) {
   MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);
   assert(_ids[id] == claimed, "Precondition.");
   _ids[id] = _hd;
   _hd = id;
   _claimed--;
 #if FID_STATS
-  tty->print("[%d] release_par_id(%d), waiters =%d,  claimed = %d.\n",
+  tty->print("[%d] release_par_id(%u), waiters =%u,  claimed = %u.\n",
              thr_self(), id, _waiters, _claimed);
 #endif
   if (_waiters > 0)
--- old/src/share/vm/gc/shared/workgroup.hpp	2015-11-11 14:22:38.361811090 -0500
+++ new/src/share/vm/gc/shared/workgroup.hpp	2015-11-11 14:22:37.037736284 -0500
@@ -381,17 +381,17 @@
 // Represents a set of free small integer ids.
 class FreeIdSet : public CHeapObj<mtInternal> {
   enum {
-    end_of_list = -1,
-    claimed = -2
+    end_of_list = UINT_MAX,
+    claimed = UINT_MAX - 1
   };
 
   int _sz;
   Monitor* _mon;
 
-  int* _ids;
-  int _hd;
-  int _waiters;
-  int _claimed;
+  uint* _ids;
+  uint _hd;
+  uint _waiters;
+  uint _claimed;
 
   static bool _safepoint;
   typedef FreeIdSet* FreeIdSetPtr;
@@ -401,20 +401,16 @@
   int _index;
 
 public:
-  FreeIdSet(int sz, Monitor* mon);
+  FreeIdSet(uint sz, Monitor* mon);
   ~FreeIdSet();
 
   static void set_safepoint(bool b);
 
-  // Attempt to claim the given id permanently.  Returns "true" iff
-  // successful.
-  bool claim_perm_id(int i);
-
   // Returns an unclaimed parallel id (waiting for one to be released if
-  // necessary).  Returns "-1" if a GC wakes up a wait for an id.
+  // necessary).  Returns "UINT_MAX" if a GC wakes up a wait for an id.
   int claim_par_id();
 
-  void release_par_id(int id);
+  void release_par_id(uint id);
 };
 
 #endif // SHARE_VM_GC_SHARED_WORKGROUP_HPP