1 /*
   2  * Copyright 2001-2009 Sun Microsystems, Inc.  All Rights Reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  20  * CA 95054 USA or visit www.sun.com if you need additional information or
  21  * have any questions.
  22  *
  23  */
  24 
  25 # include "incls/_precompiled.incl"
  26 # include "incls/_ptrQueue.cpp.incl"
  27 
  28 PtrQueue::PtrQueue(PtrQueueSet* qset_, bool perm) :
  29   _qset(qset_), _buf(NULL), _index(0), _active(false),
  30   _perm(perm), _lock(NULL)
  31 {}
  32 
  33 void PtrQueue::flush() {
  34   if (!_perm && _buf != NULL) {
  35     if (_index == _sz) {
  36       // No work to do.
  37       qset()->deallocate_buffer(_buf);
  38     } else {
  39       // We must NULL out the unused entries, then enqueue.
  40       for (size_t i = 0; i < _index; i += oopSize) {
  41         _buf[byte_index_to_index((int)i)] = NULL;
  42       }
  43       qset()->enqueue_complete_buffer(_buf);
  44     }
  45     _buf = NULL;
  46     _index = 0;
  47   }
  48 }
  49 
  50 
  51 static int byte_index_to_index(int ind) {
  52   assert((ind % oopSize) == 0, "Invariant.");
  53   return ind / oopSize;
  54 }
  55 
  56 static int index_to_byte_index(int byte_ind) {
  57   return byte_ind * oopSize;
  58 }
  59 
  60 void PtrQueue::enqueue_known_active(void* ptr) {
  61   assert(0 <= _index && _index <= _sz, "Invariant.");
  62   assert(_index == 0 || _buf != NULL, "invariant");
  63 
  64   while (_index == 0) {
  65     handle_zero_index();
  66   }
  67   assert(_index > 0, "postcondition");
  68 
  69   _index -= oopSize;
  70   _buf[byte_index_to_index((int)_index)] = ptr;
  71   assert(0 <= _index && _index <= _sz, "Invariant.");
  72 }
  73 
  74 void PtrQueue::locking_enqueue_completed_buffer(void** buf) {
  75   assert(_lock->owned_by_self(), "Required.");
  76   _lock->unlock();
  77   qset()->enqueue_complete_buffer(buf);
  78   // We must relock only because the caller will unlock, for the normal
  79   // case.
  80   _lock->lock_without_safepoint_check();
  81 }
  82 
  83 
  84 PtrQueueSet::PtrQueueSet(bool notify_when_complete) :
  85   _max_completed_queue(0),
  86   _cbl_mon(NULL), _fl_lock(NULL),
  87   _notify_when_complete(notify_when_complete),
  88   _sz(0),
  89   _completed_buffers_head(NULL),
  90   _completed_buffers_tail(NULL),
  91   _n_completed_buffers(0),
  92   _process_completed_threshold(0), _process_completed(false),
  93   _buf_free_list(NULL), _buf_free_list_sz(0)
  94 {
  95   _fl_owner = this;
  96 }
  97 
  98 void** PtrQueueSet::allocate_buffer() {
  99   assert(_sz > 0, "Didn't set a buffer size.");
 100   MutexLockerEx x(_fl_owner->_fl_lock, Mutex::_no_safepoint_check_flag);
 101   if (_fl_owner->_buf_free_list != NULL) {
 102     void** res = _fl_owner->_buf_free_list;
 103     _fl_owner->_buf_free_list = (void**)_fl_owner->_buf_free_list[0];
 104     _fl_owner->_buf_free_list_sz--;
 105     // Just override the next pointer with NULL, just in case we scan this part
 106     // of the buffer.
 107     res[0] = NULL;
 108     return res;
 109   } else {
 110     return NEW_C_HEAP_ARRAY(void*, _sz);
 111   }
 112 }
 113 
 114 void PtrQueueSet::deallocate_buffer(void** buf) {
 115   assert(_sz > 0, "Didn't set a buffer size.");
 116   MutexLockerEx x(_fl_owner->_fl_lock, Mutex::_no_safepoint_check_flag);
 117   buf[0] = (void*)_fl_owner->_buf_free_list;
 118   _fl_owner->_buf_free_list = buf;
 119   _fl_owner->_buf_free_list_sz++;
 120 }
 121 
 122 void PtrQueueSet::reduce_free_list() {
 123   // For now we'll adopt the strategy of deleting half.
 124   MutexLockerEx x(_fl_lock, Mutex::_no_safepoint_check_flag);
 125   size_t n = _buf_free_list_sz / 2;
 126   while (n > 0) {
 127     assert(_buf_free_list != NULL, "_buf_free_list_sz must be wrong.");
 128     void** head = _buf_free_list;
 129     _buf_free_list = (void**)_buf_free_list[0];
 130     FREE_C_HEAP_ARRAY(void*,head);
 131     n--;
 132   }
 133 }
 134 
 135 void PtrQueueSet::enqueue_complete_buffer(void** buf, size_t index, bool ignore_max_completed) {
 136   // I use explicit locking here because there's a bailout in the middle.
 137   _cbl_mon->lock_without_safepoint_check();
 138 
 139   Thread* thread = Thread::current();
 140   assert( ignore_max_completed ||
 141           thread->is_Java_thread() ||
 142           SafepointSynchronize::is_at_safepoint(),
 143           "invariant" );
 144   ignore_max_completed = ignore_max_completed || !thread->is_Java_thread();
 145 
 146   if (!ignore_max_completed && _max_completed_queue > 0 &&
 147       _n_completed_buffers >= (size_t) _max_completed_queue) {
 148     _cbl_mon->unlock();
 149     bool b = mut_process_buffer(buf);
 150     if (b) {
 151       deallocate_buffer(buf);
 152       return;
 153     }
 154 
 155     // Otherwise, go ahead and enqueue the buffer.  Must reaquire the lock.
 156     _cbl_mon->lock_without_safepoint_check();
 157   }
 158 
 159   // Here we still hold the _cbl_mon.
 160   CompletedBufferNode* cbn = new CompletedBufferNode;
 161   cbn->buf = buf;
 162   cbn->next = NULL;
 163   cbn->index = index;
 164   if (_completed_buffers_tail == NULL) {
 165     assert(_completed_buffers_head == NULL, "Well-formedness");
 166     _completed_buffers_head = cbn;
 167     _completed_buffers_tail = cbn;
 168   } else {
 169     _completed_buffers_tail->next = cbn;
 170     _completed_buffers_tail = cbn;
 171   }
 172   _n_completed_buffers++;
 173 
 174   if (!_process_completed &&
 175       _n_completed_buffers >= _process_completed_threshold) {
 176     _process_completed = true;
 177     if (_notify_when_complete)
 178       _cbl_mon->notify_all();
 179   }
 180   debug_only(assert_completed_buffer_list_len_correct_locked());
 181   _cbl_mon->unlock();
 182 }
 183 
 184 int PtrQueueSet::completed_buffers_list_length() {
 185   int n = 0;
 186   CompletedBufferNode* cbn = _completed_buffers_head;
 187   while (cbn != NULL) {
 188     n++;
 189     cbn = cbn->next;
 190   }
 191   return n;
 192 }
 193 
 194 void PtrQueueSet::assert_completed_buffer_list_len_correct() {
 195   MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
 196   assert_completed_buffer_list_len_correct_locked();
 197 }
 198 
 199 void PtrQueueSet::assert_completed_buffer_list_len_correct_locked() {
 200   guarantee((size_t)completed_buffers_list_length() ==  _n_completed_buffers,
 201             "Completed buffer length is wrong.");
 202 }
 203 
 204 void PtrQueueSet::set_buffer_size(size_t sz) {
 205   assert(_sz == 0 && sz > 0, "Should be called only once.");
 206   _sz = sz * oopSize;
 207 }
 208 
 209 void PtrQueueSet::set_process_completed_threshold(size_t sz) {
 210   _process_completed_threshold = sz;
 211 }
 212 
 213 // Merge lists of buffers. Notify waiting threads if the length of the list
 214 // exceeds threshold. The source queue is emptied as a result. The queues
 215 // must share the monitor.
 216 void PtrQueueSet::merge_bufferlists(PtrQueueSet *src) {
 217   assert(_cbl_mon == src->_cbl_mon, "Should share the same lock");
 218   MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
 219   if (_completed_buffers_tail == NULL) {
 220     assert(_completed_buffers_head == NULL, "Well-formedness");
 221     _completed_buffers_head = src->_completed_buffers_head;
 222     _completed_buffers_tail = src->_completed_buffers_tail;
 223   } else {
 224     assert(_completed_buffers_head != NULL, "Well formedness");
 225     if (src->_completed_buffers_head != NULL) {
 226       _completed_buffers_tail->next = src->_completed_buffers_head;
 227       _completed_buffers_tail = src->_completed_buffers_tail;
 228     }
 229   }
 230   _n_completed_buffers += src->_n_completed_buffers;
 231 
 232   src->_n_completed_buffers = 0;
 233   src->_completed_buffers_head = NULL;
 234   src->_completed_buffers_tail = NULL;
 235 
 236   assert(_completed_buffers_head == NULL && _completed_buffers_tail == NULL ||
 237          _completed_buffers_head != NULL && _completed_buffers_tail != NULL,
 238          "Sanity");
 239 
 240   if (!_process_completed &&
 241       _n_completed_buffers >= _process_completed_threshold) {
 242     _process_completed = true;
 243     if (_notify_when_complete)
 244       _cbl_mon->notify_all();
 245   }
 246 }
 247 
 248 // Merge free lists of the two queues. The free list of the source
 249 // queue is emptied as a result. The queues must share the same
 250 // mutex that guards free lists.
 251 void PtrQueueSet::merge_freelists(PtrQueueSet* src) {
 252   assert(_fl_lock == src->_fl_lock, "Should share the same lock");
 253   MutexLockerEx x(_fl_lock, Mutex::_no_safepoint_check_flag);
 254   if (_buf_free_list != NULL) {
 255     void **p = _buf_free_list;
 256     while (*p != NULL) {
 257       p = (void**)*p;
 258     }
 259     *p = src->_buf_free_list;
 260   } else {
 261     _buf_free_list = src->_buf_free_list;
 262   }
 263   _buf_free_list_sz += src->_buf_free_list_sz;
 264   src->_buf_free_list = NULL;
 265   src->_buf_free_list_sz = 0;
 266 }