1 /* 2 * Copyright (c) 1998, 2020, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "gc/shared/oopStorage.inline.hpp" 27 #include "gc/shared/oopStorageSet.hpp" 28 #include "logging/log.hpp" 29 #include "memory/iterator.hpp" 30 #include "memory/universe.hpp" 31 #include "oops/access.inline.hpp" 32 #include "oops/oop.inline.hpp" 33 #include "runtime/handles.inline.hpp" 34 #include "runtime/jniHandles.inline.hpp" 35 #include "runtime/mutexLocker.hpp" 36 #include "runtime/thread.inline.hpp" 37 #include "utilities/align.hpp" 38 #include "utilities/debug.hpp" 39 40 OopStorage* JNIHandles::global_handles() { 41 return _global_handles; 42 } 43 44 OopStorage* JNIHandles::weak_global_handles() { 45 return _weak_global_handles; 46 } 47 48 // Serviceability agent support. 49 OopStorage* JNIHandles::_global_handles = NULL; 50 OopStorage* JNIHandles::_weak_global_handles = NULL; 51 52 void jni_handles_init() { 53 JNIHandles::_global_handles = OopStorageSet::create_strong("JNI Global"); 54 JNIHandles::_weak_global_handles = OopStorageSet::create_weak("JNI Weak"); 55 } 56 57 jobject JNIHandles::make_local(oop obj) { 58 if (obj == NULL) { 59 return NULL; // ignore null handles 60 } else { 61 Thread* thread = Thread::current(); 62 assert(oopDesc::is_oop(obj), "not an oop"); 63 assert(!current_thread_in_native(), "must not be in native"); 64 return thread->active_handles()->allocate_handle(obj); 65 } 66 } 67 68 69 // optimized versions 70 71 jobject JNIHandles::make_local(Thread* thread, oop obj) { 72 if (obj == NULL) { 73 return NULL; // ignore null handles 74 } else { 75 assert(oopDesc::is_oop(obj), "not an oop"); 76 assert(thread->is_Java_thread(), "not a Java thread"); 77 assert(!current_thread_in_native(), "must not be in native"); 78 return thread->active_handles()->allocate_handle(obj); 79 } 80 } 81 82 83 jobject JNIHandles::make_local(JNIEnv* env, oop obj) { 84 if (obj == NULL) { 85 return NULL; // ignore null handles 86 } else { 87 JavaThread* thread = JavaThread::thread_from_jni_environment(env); 88 assert(oopDesc::is_oop(obj), "not an oop"); 89 assert(!current_thread_in_native(), "must not be in native"); 90 return thread->active_handles()->allocate_handle(obj); 91 } 92 } 93 94 95 static void report_handle_allocation_failure(AllocFailType alloc_failmode, 96 const char* handle_kind) { 97 if (alloc_failmode == AllocFailStrategy::EXIT_OOM) { 98 // Fake size value, since we don't know the min allocation size here. 99 vm_exit_out_of_memory(sizeof(oop), OOM_MALLOC_ERROR, 100 "Cannot create %s JNI handle", handle_kind); 101 } else { 102 assert(alloc_failmode == AllocFailStrategy::RETURN_NULL, "invariant"); 103 } 104 } 105 106 jobject JNIHandles::make_global(Handle obj, AllocFailType alloc_failmode) { 107 assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC"); 108 assert(!current_thread_in_native(), "must not be in native"); 109 jobject res = NULL; 110 if (!obj.is_null()) { 111 // ignore null handles 112 assert(oopDesc::is_oop(obj()), "not an oop"); 113 oop* ptr = global_handles()->allocate(); 114 // Return NULL on allocation failure. 115 if (ptr != NULL) { 116 assert(*ptr == NULL, "invariant"); 117 NativeAccess<>::oop_store(ptr, obj()); 118 res = reinterpret_cast<jobject>(ptr); 119 } else { 120 report_handle_allocation_failure(alloc_failmode, "global"); 121 } 122 } 123 124 return res; 125 } 126 127 128 jobject JNIHandles::make_weak_global(Handle obj, AllocFailType alloc_failmode) { 129 assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC"); 130 assert(!current_thread_in_native(), "must not be in native"); 131 jobject res = NULL; 132 if (!obj.is_null()) { 133 // ignore null handles 134 assert(oopDesc::is_oop(obj()), "not an oop"); 135 oop* ptr = weak_global_handles()->allocate(); 136 // Return NULL on allocation failure. 137 if (ptr != NULL) { 138 assert(*ptr == NULL, "invariant"); 139 NativeAccess<ON_PHANTOM_OOP_REF>::oop_store(ptr, obj()); 140 char* tptr = reinterpret_cast<char*>(ptr) + weak_tag_value; 141 res = reinterpret_cast<jobject>(tptr); 142 } else { 143 report_handle_allocation_failure(alloc_failmode, "weak global"); 144 } 145 } 146 return res; 147 } 148 149 // Resolve some erroneous cases to NULL, rather than treating them as 150 // possibly unchecked errors. In particular, deleted handles are 151 // treated as NULL (though a deleted and later reallocated handle 152 // isn't detected). 153 oop JNIHandles::resolve_external_guard(jobject handle) { 154 oop result = NULL; 155 if (handle != NULL) { 156 result = resolve_impl<DECORATORS_NONE, true /* external_guard */>(handle); 157 } 158 return result; 159 } 160 161 bool JNIHandles::is_global_weak_cleared(jweak handle) { 162 assert(handle != NULL, "precondition"); 163 assert(is_jweak(handle), "not a weak handle"); 164 oop* oop_ptr = jweak_ptr(handle); 165 oop value = NativeAccess<ON_PHANTOM_OOP_REF | AS_NO_KEEPALIVE>::oop_load(oop_ptr); 166 return value == NULL; 167 } 168 169 void JNIHandles::destroy_global(jobject handle) { 170 if (handle != NULL) { 171 assert(!is_jweak(handle), "wrong method for detroying jweak"); 172 oop* oop_ptr = jobject_ptr(handle); 173 NativeAccess<>::oop_store(oop_ptr, (oop)NULL); 174 global_handles()->release(oop_ptr); 175 } 176 } 177 178 179 void JNIHandles::destroy_weak_global(jobject handle) { 180 if (handle != NULL) { 181 assert(is_jweak(handle), "JNI handle not jweak"); 182 oop* oop_ptr = jweak_ptr(handle); 183 NativeAccess<ON_PHANTOM_OOP_REF>::oop_store(oop_ptr, (oop)NULL); 184 weak_global_handles()->release(oop_ptr); 185 } 186 } 187 188 189 void JNIHandles::oops_do(OopClosure* f) { 190 global_handles()->oops_do(f); 191 } 192 193 194 void JNIHandles::weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f) { 195 weak_global_handles()->weak_oops_do(is_alive, f); 196 } 197 198 199 void JNIHandles::weak_oops_do(OopClosure* f) { 200 weak_global_handles()->weak_oops_do(f); 201 } 202 203 bool JNIHandles::is_global_storage(const OopStorage* storage) { 204 return _global_handles == storage; 205 } 206 207 inline bool is_storage_handle(const OopStorage* storage, const oop* ptr) { 208 return storage->allocation_status(ptr) == OopStorage::ALLOCATED_ENTRY; 209 } 210 211 212 jobjectRefType JNIHandles::handle_type(Thread* thread, jobject handle) { 213 assert(handle != NULL, "precondition"); 214 jobjectRefType result = JNIInvalidRefType; 215 if (is_jweak(handle)) { 216 if (is_storage_handle(weak_global_handles(), jweak_ptr(handle))) { 217 result = JNIWeakGlobalRefType; 218 } 219 } else { 220 switch (global_handles()->allocation_status(jobject_ptr(handle))) { 221 case OopStorage::ALLOCATED_ENTRY: 222 result = JNIGlobalRefType; 223 break; 224 225 case OopStorage::UNALLOCATED_ENTRY: 226 break; // Invalid global handle 227 228 case OopStorage::INVALID_ENTRY: 229 // Not in global storage. Might be a local handle. 230 if (is_local_handle(thread, handle) || 231 (thread->is_Java_thread() && 232 is_frame_handle((JavaThread*)thread, handle))) { 233 result = JNILocalRefType; 234 } 235 break; 236 237 default: 238 ShouldNotReachHere(); 239 } 240 } 241 return result; 242 } 243 244 245 bool JNIHandles::is_local_handle(Thread* thread, jobject handle) { 246 assert(handle != NULL, "precondition"); 247 JNIHandleBlock* block = thread->active_handles(); 248 249 // Look back past possible native calls to jni_PushLocalFrame. 250 while (block != NULL) { 251 if (block->chain_contains(handle)) { 252 return true; 253 } 254 block = block->pop_frame_link(); 255 } 256 return false; 257 } 258 259 260 // Determine if the handle is somewhere in the current thread's stack. 261 // We easily can't isolate any particular stack frame the handle might 262 // come from, so we'll check the whole stack. 263 264 bool JNIHandles::is_frame_handle(JavaThread* thr, jobject handle) { 265 assert(handle != NULL, "precondition"); 266 // If there is no java frame, then this must be top level code, such 267 // as the java command executable, in which case, this type of handle 268 // is not permitted. 269 return (thr->has_last_Java_frame() && 270 thr->is_in_stack_range_incl((address)handle, (address)thr->last_Java_sp())); 271 } 272 273 274 bool JNIHandles::is_global_handle(jobject handle) { 275 assert(handle != NULL, "precondition"); 276 return !is_jweak(handle) && is_storage_handle(global_handles(), jobject_ptr(handle)); 277 } 278 279 280 bool JNIHandles::is_weak_global_handle(jobject handle) { 281 assert(handle != NULL, "precondition"); 282 return is_jweak(handle) && is_storage_handle(weak_global_handles(), jweak_ptr(handle)); 283 } 284 285 size_t JNIHandles::global_handle_memory_usage() { 286 return global_handles()->total_memory_usage(); 287 } 288 289 size_t JNIHandles::weak_global_handle_memory_usage() { 290 return weak_global_handles()->total_memory_usage(); 291 } 292 293 294 // We assume this is called at a safepoint: no lock is needed. 295 void JNIHandles::print_on(outputStream* st) { 296 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint"); 297 298 st->print_cr("JNI global refs: " SIZE_FORMAT ", weak refs: " SIZE_FORMAT, 299 global_handles()->allocation_count(), 300 weak_global_handles()->allocation_count()); 301 st->cr(); 302 st->flush(); 303 } 304 305 void JNIHandles::print() { print_on(tty); } 306 307 class VerifyJNIHandles: public OopClosure { 308 public: 309 virtual void do_oop(oop* root) { 310 guarantee(oopDesc::is_oop_or_null(RawAccess<>::oop_load(root)), "Invalid oop"); 311 } 312 virtual void do_oop(narrowOop* root) { ShouldNotReachHere(); } 313 }; 314 315 void JNIHandles::verify() { 316 VerifyJNIHandles verify_handle; 317 318 oops_do(&verify_handle); 319 weak_oops_do(&verify_handle); 320 } 321 322 // This method is implemented here to avoid circular includes between 323 // jniHandles.hpp and thread.hpp. 324 bool JNIHandles::current_thread_in_native() { 325 Thread* thread = Thread::current(); 326 return (thread->is_Java_thread() && 327 JavaThread::current()->thread_state() == _thread_in_native); 328 } 329 330 331 int JNIHandleBlock::_blocks_allocated = 0; 332 JNIHandleBlock* JNIHandleBlock::_block_free_list = NULL; 333 #ifndef PRODUCT 334 JNIHandleBlock* JNIHandleBlock::_block_list = NULL; 335 #endif 336 337 static inline bool is_tagged_free_list(uintptr_t value) { 338 return (value & 1u) != 0; 339 } 340 341 static inline uintptr_t tag_free_list(uintptr_t value) { 342 return value | 1u; 343 } 344 345 static inline uintptr_t untag_free_list(uintptr_t value) { 346 return value & ~(uintptr_t)1u; 347 } 348 349 // There is a freelist of handles running through the JNIHandleBlock 350 // with a tagged next pointer, distinguishing these next pointers from 351 // oops. The freelist handling currently relies on the size of oops 352 // being the same as a native pointer. If this ever changes, then 353 // this freelist handling must change too. 354 STATIC_ASSERT(sizeof(oop) == sizeof(uintptr_t)); 355 356 #ifdef ASSERT 357 void JNIHandleBlock::zap() { 358 // Zap block values 359 _top = 0; 360 for (int index = 0; index < block_size_in_oops; index++) { 361 // NOT using Access here; just bare clobbering to NULL, since the 362 // block no longer contains valid oops. 363 _handles[index] = 0; 364 } 365 } 366 #endif // ASSERT 367 368 JNIHandleBlock* JNIHandleBlock::allocate_block(Thread* thread) { 369 assert(thread == NULL || thread == Thread::current(), "sanity check"); 370 JNIHandleBlock* block; 371 // Check the thread-local free list for a block so we don't 372 // have to acquire a mutex. 373 if (thread != NULL && thread->free_handle_block() != NULL) { 374 block = thread->free_handle_block(); 375 thread->set_free_handle_block(block->_next); 376 } 377 else { 378 // locking with safepoint checking introduces a potential deadlock: 379 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock 380 // - another would hold Threads_lock (jni_AttachCurrentThread) and then 381 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block) 382 MutexLocker ml(JNIHandleBlockFreeList_lock, 383 Mutex::_no_safepoint_check_flag); 384 if (_block_free_list == NULL) { 385 // Allocate new block 386 block = new JNIHandleBlock(); 387 _blocks_allocated++; 388 block->zap(); 389 #ifndef PRODUCT 390 // Link new block to list of all allocated blocks 391 block->_block_list_link = _block_list; 392 _block_list = block; 393 #endif 394 } else { 395 // Get block from free list 396 block = _block_free_list; 397 _block_free_list = _block_free_list->_next; 398 } 399 } 400 block->_top = 0; 401 block->_next = NULL; 402 block->_pop_frame_link = NULL; 403 block->_planned_capacity = block_size_in_oops; 404 // _last, _free_list & _allocate_before_rebuild initialized in allocate_handle 405 debug_only(block->_last = NULL); 406 debug_only(block->_free_list = NULL); 407 debug_only(block->_allocate_before_rebuild = -1); 408 return block; 409 } 410 411 412 void JNIHandleBlock::release_block(JNIHandleBlock* block, Thread* thread) { 413 assert(thread == NULL || thread == Thread::current(), "sanity check"); 414 JNIHandleBlock* pop_frame_link = block->pop_frame_link(); 415 // Put returned block at the beginning of the thread-local free list. 416 // Note that if thread == NULL, we use it as an implicit argument that 417 // we _don't_ want the block to be kept on the free_handle_block. 418 // See for instance JavaThread::exit(). 419 if (thread != NULL ) { 420 block->zap(); 421 JNIHandleBlock* freelist = thread->free_handle_block(); 422 block->_pop_frame_link = NULL; 423 thread->set_free_handle_block(block); 424 425 // Add original freelist to end of chain 426 if ( freelist != NULL ) { 427 while ( block->_next != NULL ) block = block->_next; 428 block->_next = freelist; 429 } 430 block = NULL; 431 } 432 if (block != NULL) { 433 // Return blocks to free list 434 // locking with safepoint checking introduces a potential deadlock: 435 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock 436 // - another would hold Threads_lock (jni_AttachCurrentThread) and then 437 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block) 438 MutexLocker ml(JNIHandleBlockFreeList_lock, 439 Mutex::_no_safepoint_check_flag); 440 while (block != NULL) { 441 block->zap(); 442 JNIHandleBlock* next = block->_next; 443 block->_next = _block_free_list; 444 _block_free_list = block; 445 block = next; 446 } 447 } 448 if (pop_frame_link != NULL) { 449 // As a sanity check we release blocks pointed to by the pop_frame_link. 450 // This should never happen (only if PopLocalFrame is not called the 451 // correct number of times). 452 release_block(pop_frame_link, thread); 453 } 454 } 455 456 457 void JNIHandleBlock::oops_do(OopClosure* f) { 458 JNIHandleBlock* current_chain = this; 459 // Iterate over chain of blocks, followed by chains linked through the 460 // pop frame links. 461 while (current_chain != NULL) { 462 for (JNIHandleBlock* current = current_chain; current != NULL; 463 current = current->_next) { 464 assert(current == current_chain || current->pop_frame_link() == NULL, 465 "only blocks first in chain should have pop frame link set"); 466 for (int index = 0; index < current->_top; index++) { 467 uintptr_t* addr = &(current->_handles)[index]; 468 uintptr_t value = *addr; 469 // traverse heap pointers only, not deleted handles or free list 470 // pointers 471 if (value != 0 && !is_tagged_free_list(value)) { 472 oop* root = (oop*)addr; 473 f->do_oop(root); 474 } 475 } 476 // the next handle block is valid only if current block is full 477 if (current->_top < block_size_in_oops) { 478 break; 479 } 480 } 481 current_chain = current_chain->pop_frame_link(); 482 } 483 } 484 485 486 jobject JNIHandleBlock::allocate_handle(oop obj) { 487 assert(Universe::heap()->is_in(obj), "sanity check"); 488 if (_top == 0) { 489 // This is the first allocation or the initial block got zapped when 490 // entering a native function. If we have any following blocks they are 491 // not valid anymore. 492 for (JNIHandleBlock* current = _next; current != NULL; 493 current = current->_next) { 494 assert(current->_last == NULL, "only first block should have _last set"); 495 assert(current->_free_list == NULL, 496 "only first block should have _free_list set"); 497 if (current->_top == 0) { 498 // All blocks after the first clear trailing block are already cleared. 499 #ifdef ASSERT 500 for (current = current->_next; current != NULL; current = current->_next) { 501 assert(current->_top == 0, "trailing blocks must already be cleared"); 502 } 503 #endif 504 break; 505 } 506 current->_top = 0; 507 current->zap(); 508 } 509 // Clear initial block 510 _free_list = NULL; 511 _allocate_before_rebuild = 0; 512 _last = this; 513 zap(); 514 } 515 516 // Try last block 517 if (_last->_top < block_size_in_oops) { 518 oop* handle = (oop*)&(_last->_handles)[_last->_top++]; 519 NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, obj); 520 return (jobject) handle; 521 } 522 523 // Try free list 524 if (_free_list != NULL) { 525 oop* handle = (oop*)_free_list; 526 _free_list = (uintptr_t*) untag_free_list(*_free_list); 527 NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, obj); 528 return (jobject) handle; 529 } 530 // Check if unused block follow last 531 if (_last->_next != NULL) { 532 // update last and retry 533 _last = _last->_next; 534 return allocate_handle(obj); 535 } 536 537 // No space available, we have to rebuild free list or expand 538 if (_allocate_before_rebuild == 0) { 539 rebuild_free_list(); // updates _allocate_before_rebuild counter 540 } else { 541 // Append new block 542 Thread* thread = Thread::current(); 543 Handle obj_handle(thread, obj); 544 // This can block, so we need to preserve obj across call. 545 _last->_next = JNIHandleBlock::allocate_block(thread); 546 _last = _last->_next; 547 _allocate_before_rebuild--; 548 obj = obj_handle(); 549 } 550 return allocate_handle(obj); // retry 551 } 552 553 void JNIHandleBlock::rebuild_free_list() { 554 assert(_allocate_before_rebuild == 0 && _free_list == NULL, "just checking"); 555 int free = 0; 556 int blocks = 0; 557 for (JNIHandleBlock* current = this; current != NULL; current = current->_next) { 558 for (int index = 0; index < current->_top; index++) { 559 uintptr_t* handle = &(current->_handles)[index]; 560 if (*handle == 0) { 561 // this handle was cleared out by a delete call, reuse it 562 *handle = _free_list == NULL ? 0 : tag_free_list((uintptr_t)_free_list); 563 _free_list = handle; 564 free++; 565 } 566 } 567 // we should not rebuild free list if there are unused handles at the end 568 assert(current->_top == block_size_in_oops, "just checking"); 569 blocks++; 570 } 571 // Heuristic: if more than half of the handles are free we rebuild next time 572 // as well, otherwise we append a corresponding number of new blocks before 573 // attempting a free list rebuild again. 574 int total = blocks * block_size_in_oops; 575 int extra = total - 2*free; 576 if (extra > 0) { 577 // Not as many free handles as we would like - compute number of new blocks to append 578 _allocate_before_rebuild = (extra + block_size_in_oops - 1) / block_size_in_oops; 579 } 580 } 581 582 583 bool JNIHandleBlock::contains(jobject handle) const { 584 return ((jobject)&_handles[0] <= handle && handle<(jobject)&_handles[_top]); 585 } 586 587 588 bool JNIHandleBlock::chain_contains(jobject handle) const { 589 for (JNIHandleBlock* current = (JNIHandleBlock*) this; current != NULL; current = current->_next) { 590 if (current->contains(handle)) { 591 return true; 592 } 593 } 594 return false; 595 } 596 597 598 size_t JNIHandleBlock::length() const { 599 size_t result = 1; 600 for (JNIHandleBlock* current = _next; current != NULL; current = current->_next) { 601 result++; 602 } 603 return result; 604 } 605 606 class CountJNIHandleClosure: public OopClosure { 607 private: 608 int _count; 609 public: 610 CountJNIHandleClosure(): _count(0) {} 611 virtual void do_oop(oop* ooph) { _count++; } 612 virtual void do_oop(narrowOop* unused) { ShouldNotReachHere(); } 613 int count() { return _count; } 614 }; 615 616 const size_t JNIHandleBlock::get_number_of_live_handles() { 617 CountJNIHandleClosure counter; 618 oops_do(&counter); 619 return counter.count(); 620 } 621 622 // This method is not thread-safe, i.e., must be called while holding a lock on the 623 // structure. 624 size_t JNIHandleBlock::memory_usage() const { 625 return length() * sizeof(JNIHandleBlock); 626 } 627 628 629 #ifndef PRODUCT 630 631 bool JNIHandles::is_local_handle(jobject handle) { 632 return JNIHandleBlock::any_contains(handle); 633 } 634 635 bool JNIHandleBlock::any_contains(jobject handle) { 636 assert(handle != NULL, "precondition"); 637 for (JNIHandleBlock* current = _block_list; current != NULL; current = current->_block_list_link) { 638 if (current->contains(handle)) { 639 return true; 640 } 641 } 642 return false; 643 } 644 645 void JNIHandleBlock::print_statistics() { 646 int used_blocks = 0; 647 int free_blocks = 0; 648 int used_handles = 0; 649 int free_handles = 0; 650 JNIHandleBlock* block = _block_list; 651 while (block != NULL) { 652 if (block->_top > 0) { 653 used_blocks++; 654 } else { 655 free_blocks++; 656 } 657 used_handles += block->_top; 658 free_handles += (block_size_in_oops - block->_top); 659 block = block->_block_list_link; 660 } 661 tty->print_cr("JNIHandleBlocks statistics"); 662 tty->print_cr("- blocks allocated: %d", used_blocks + free_blocks); 663 tty->print_cr("- blocks in use: %d", used_blocks); 664 tty->print_cr("- blocks free: %d", free_blocks); 665 tty->print_cr("- handles in use: %d", used_handles); 666 tty->print_cr("- handles free: %d", free_handles); 667 } 668 669 #endif