1 /*
2 * Copyright (c) 1998, 2021, 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 "classfile/vmSymbols.hpp"
27 #include "gc/shared/collectedHeap.hpp"
28 #include "gc/shared/oopStorage.inline.hpp"
29 #include "gc/shared/oopStorageSet.hpp"
30 #include "logging/log.hpp"
31 #include "memory/iterator.hpp"
32 #include "memory/universe.hpp"
33 #include "oops/access.inline.hpp"
34 #include "oops/oop.inline.hpp"
35 #include "runtime/handles.inline.hpp"
36 #include "runtime/javaCalls.hpp"
37 #include "runtime/jniHandles.inline.hpp"
38 #include "runtime/mutexLocker.hpp"
39 #include "runtime/thread.inline.hpp"
40 #include "utilities/align.hpp"
41 #include "utilities/debug.hpp"
42
43 OopStorage* JNIHandles::global_handles() {
44 return _global_handles;
45 }
46
47 OopStorage* JNIHandles::weak_global_handles() {
48 return _weak_global_handles;
49 }
50
51 // Serviceability agent support.
52 OopStorage* JNIHandles::_global_handles = NULL;
53 OopStorage* JNIHandles::_weak_global_handles = NULL;
54
55 void jni_handles_init() {
56 JNIHandles::_global_handles = OopStorageSet::create_strong("JNI Global", mtInternal);
57 JNIHandles::_weak_global_handles = OopStorageSet::create_weak("JNI Weak", mtInternal);
58 }
59
60 jobject JNIHandles::make_local(oop obj) {
61 return make_local(Thread::current(), obj);
62 }
63
64 // Used by NewLocalRef which requires NULL on out-of-memory
65 jobject JNIHandles::make_local(Thread* thread, oop obj, AllocFailType alloc_failmode) {
66 if (obj == NULL) {
67 return NULL; // ignore null handles
68 } else {
69 assert(oopDesc::is_oop(obj), "not an oop");
70 assert(thread->is_Java_thread(), "not a Java thread");
71 assert(!current_thread_in_native(), "must not be in native");
72 return thread->active_handles()->allocate_handle(obj, alloc_failmode);
73 }
74 }
75
76 static void report_handle_allocation_failure(AllocFailType alloc_failmode,
77 const char* handle_kind) {
78 if (alloc_failmode == AllocFailStrategy::EXIT_OOM) {
79 // Fake size value, since we don't know the min allocation size here.
80 vm_exit_out_of_memory(sizeof(oop), OOM_MALLOC_ERROR,
81 "Cannot create %s JNI handle", handle_kind);
82 } else {
83 assert(alloc_failmode == AllocFailStrategy::RETURN_NULL, "invariant");
84 }
85 }
86
87 jobject JNIHandles::make_global(Handle obj, AllocFailType alloc_failmode) {
88 assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");
89 assert(!current_thread_in_native(), "must not be in native");
90 jobject res = NULL;
91 if (!obj.is_null()) {
92 // ignore null handles
93 assert(oopDesc::is_oop(obj()), "not an oop");
94 oop* ptr = global_handles()->allocate();
95 // Return NULL on allocation failure.
96 if (ptr != NULL) {
97 assert(*ptr == NULL, "invariant");
98 NativeAccess<>::oop_store(ptr, obj());
99 res = reinterpret_cast<jobject>(ptr);
100 } else {
101 report_handle_allocation_failure(alloc_failmode, "global");
102 }
103 }
104
105 return res;
106 }
107
108 jobject JNIHandles::make_weak_global(Handle obj, AllocFailType alloc_failmode) {
109 assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");
110 assert(!current_thread_in_native(), "must not be in native");
111 jobject res = NULL;
112 if (!obj.is_null()) {
113 // ignore null handles
114 assert(oopDesc::is_oop(obj()), "not an oop");
115 oop* ptr = weak_global_handles()->allocate();
116 // Return NULL on allocation failure.
117 if (ptr != NULL) {
118 assert(*ptr == NULL, "invariant");
119 NativeAccess<ON_PHANTOM_OOP_REF>::oop_store(ptr, obj());
120 char* tptr = reinterpret_cast<char*>(ptr) + weak_tag_value;
121 res = reinterpret_cast<jobject>(tptr);
122 } else {
123 report_handle_allocation_failure(alloc_failmode, "weak global");
124 }
125 }
126 return res;
127 }
128
129 // Resolve some erroneous cases to NULL, rather than treating them as
130 // possibly unchecked errors. In particular, deleted handles are
131 // treated as NULL (though a deleted and later reallocated handle
132 // isn't detected).
133 oop JNIHandles::resolve_external_guard(jobject handle) {
134 oop result = NULL;
135 if (handle != NULL) {
136 result = resolve_impl<DECORATORS_NONE, true /* external_guard */>(handle);
137 }
138 return result;
139 }
140
141 bool JNIHandles::is_global_weak_cleared(jweak handle) {
142 assert(handle != NULL, "precondition");
143 assert(is_jweak(handle), "not a weak handle");
144 oop* oop_ptr = jweak_ptr(handle);
145 oop value = NativeAccess<ON_PHANTOM_OOP_REF | AS_NO_KEEPALIVE>::oop_load(oop_ptr);
146 return value == NULL;
147 }
148
149 void JNIHandles::destroy_global(jobject handle) {
150 if (handle != NULL) {
151 assert(!is_jweak(handle), "wrong method for detroying jweak");
152 oop* oop_ptr = jobject_ptr(handle);
153 NativeAccess<>::oop_store(oop_ptr, (oop)NULL);
154 global_handles()->release(oop_ptr);
155 }
156 }
157
158
159 void JNIHandles::destroy_weak_global(jobject handle) {
160 if (handle != NULL) {
161 assert(is_jweak(handle), "JNI handle not jweak");
162 oop* oop_ptr = jweak_ptr(handle);
163 NativeAccess<ON_PHANTOM_OOP_REF>::oop_store(oop_ptr, (oop)NULL);
164 weak_global_handles()->release(oop_ptr);
165 }
166 }
167
168
169 void JNIHandles::oops_do(OopClosure* f) {
170 global_handles()->oops_do(f);
171 }
172
173
174 void JNIHandles::weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f) {
175 weak_global_handles()->weak_oops_do(is_alive, f);
176 }
177
178
179 void JNIHandles::weak_oops_do(OopClosure* f) {
180 weak_global_handles()->weak_oops_do(f);
181 }
182
183 bool JNIHandles::is_global_storage(const OopStorage* storage) {
184 return _global_handles == storage;
185 }
186
187 inline bool is_storage_handle(const OopStorage* storage, const oop* ptr) {
188 return storage->allocation_status(ptr) == OopStorage::ALLOCATED_ENTRY;
189 }
190
191
192 jobjectRefType JNIHandles::handle_type(Thread* thread, jobject handle) {
193 assert(handle != NULL, "precondition");
194 jobjectRefType result = JNIInvalidRefType;
195 if (is_jweak(handle)) {
196 if (is_storage_handle(weak_global_handles(), jweak_ptr(handle))) {
197 result = JNIWeakGlobalRefType;
198 }
199 } else {
200 switch (global_handles()->allocation_status(jobject_ptr(handle))) {
201 case OopStorage::ALLOCATED_ENTRY:
202 result = JNIGlobalRefType;
203 break;
204
205 case OopStorage::UNALLOCATED_ENTRY:
206 break; // Invalid global handle
207
208 case OopStorage::INVALID_ENTRY:
209 // Not in global storage. Might be a local handle.
210 if (is_local_handle(thread, handle) ||
211 (thread->is_Java_thread() &&
212 is_frame_handle(JavaThread::cast(thread), handle))) {
213 result = JNILocalRefType;
214 }
215 break;
216
217 default:
218 ShouldNotReachHere();
219 }
220 }
221 return result;
222 }
223
224
225 bool JNIHandles::is_local_handle(Thread* thread, jobject handle) {
226 assert(handle != NULL, "precondition");
227 JNIHandleBlock* block = thread->active_handles();
228
229 // Look back past possible native calls to jni_PushLocalFrame.
230 while (block != NULL) {
231 if (block->chain_contains(handle)) {
232 return true;
233 }
234 block = block->pop_frame_link();
235 }
236 return false;
237 }
238
239
240 // Determine if the handle is somewhere in the current thread's stack.
241 // We easily can't isolate any particular stack frame the handle might
242 // come from, so we'll check the whole stack.
243
244 bool JNIHandles::is_frame_handle(JavaThread* thr, jobject handle) {
245 assert(handle != NULL, "precondition");
246 // If there is no java frame, then this must be top level code, such
247 // as the java command executable, in which case, this type of handle
248 // is not permitted.
249 return (thr->has_last_Java_frame() &&
250 thr->is_in_stack_range_incl((address)handle, (address)thr->last_Java_sp()));
251 }
252
253
254 bool JNIHandles::is_global_handle(jobject handle) {
255 assert(handle != NULL, "precondition");
256 return !is_jweak(handle) && is_storage_handle(global_handles(), jobject_ptr(handle));
257 }
258
259
260 bool JNIHandles::is_weak_global_handle(jobject handle) {
261 assert(handle != NULL, "precondition");
262 return is_jweak(handle) && is_storage_handle(weak_global_handles(), jweak_ptr(handle));
263 }
264
265 size_t JNIHandles::global_handle_memory_usage() {
266 return global_handles()->total_memory_usage();
267 }
268
269 size_t JNIHandles::weak_global_handle_memory_usage() {
270 return weak_global_handles()->total_memory_usage();
271 }
272
273
274 // We assume this is called at a safepoint: no lock is needed.
275 void JNIHandles::print_on(outputStream* st) {
276 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
277
278 st->print_cr("JNI global refs: " SIZE_FORMAT ", weak refs: " SIZE_FORMAT,
279 global_handles()->allocation_count(),
280 weak_global_handles()->allocation_count());
281 st->cr();
282 st->flush();
283 }
284
285 void JNIHandles::print() { print_on(tty); }
286
287 class VerifyJNIHandles: public OopClosure {
288 public:
289 virtual void do_oop(oop* root) {
290 guarantee(oopDesc::is_oop_or_null(RawAccess<>::oop_load(root)), "Invalid oop");
291 }
292 virtual void do_oop(narrowOop* root) { ShouldNotReachHere(); }
293 };
294
295 void JNIHandles::verify() {
296 VerifyJNIHandles verify_handle;
297
298 oops_do(&verify_handle);
299 weak_oops_do(&verify_handle);
300 }
301
302 // This method is implemented here to avoid circular includes between
303 // jniHandles.hpp and thread.hpp.
304 bool JNIHandles::current_thread_in_native() {
305 Thread* thread = Thread::current();
306 return (thread->is_Java_thread() &&
307 JavaThread::cast(thread)->thread_state() == _thread_in_native);
308 }
309
310 bool JNIHandles::is_same_object(jobject handle1, jobject handle2) {
311 oop obj1 = resolve_no_keepalive(handle1);
312 oop obj2 = resolve_no_keepalive(handle2);
313
314 bool ret = obj1 == obj2;
315
316 if (EnableValhalla) {
317 if (!ret && obj1 != NULL && obj2 != NULL && obj1->klass() == obj2->klass() && obj1->klass()->is_inline_klass()) {
318 // The two references are different, they are not null and they are both inline types,
319 // a full substitutability test is required, calling PrimitiveObjectMethods.isSubstitutable()
320 // (similarly to InterpreterRuntime::is_substitutable)
321 JavaThread* THREAD = JavaThread::current();
322 Handle ha(THREAD, obj1);
323 Handle hb(THREAD, obj2);
324 JavaValue result(T_BOOLEAN);
325 JavaCallArguments args;
326 args.push_oop(ha);
327 args.push_oop(hb);
328 methodHandle method(THREAD, Universe::is_substitutable_method());
329 JavaCalls::call(&result, method, &args, THREAD);
330 if (HAS_PENDING_EXCEPTION) {
331 // Something really bad happened because isSubstitutable() should not throw exceptions
332 // If it is an error, just let it propagate
333 // If it is an exception, wrap it into an InternalError
334 if (!PENDING_EXCEPTION->is_a(vmClasses::Error_klass())) {
335 Handle e(THREAD, PENDING_EXCEPTION);
336 CLEAR_PENDING_EXCEPTION;
337 THROW_MSG_CAUSE_(vmSymbols::java_lang_InternalError(), "Internal error in substitutability test", e, false);
338 }
339 }
340 ret = result.get_jboolean();
341 }
342 }
343
344 return ret;
345 }
346
347
348 int JNIHandleBlock::_blocks_allocated = 0;
349 JNIHandleBlock* JNIHandleBlock::_block_free_list = NULL;
350 #ifndef PRODUCT
351 JNIHandleBlock* JNIHandleBlock::_block_list = NULL;
352 #endif
353
354 static inline bool is_tagged_free_list(uintptr_t value) {
355 return (value & 1u) != 0;
356 }
357
358 static inline uintptr_t tag_free_list(uintptr_t value) {
359 return value | 1u;
360 }
361
362 static inline uintptr_t untag_free_list(uintptr_t value) {
363 return value & ~(uintptr_t)1u;
364 }
365
366 // There is a freelist of handles running through the JNIHandleBlock
367 // with a tagged next pointer, distinguishing these next pointers from
368 // oops. The freelist handling currently relies on the size of oops
369 // being the same as a native pointer. If this ever changes, then
370 // this freelist handling must change too.
371 STATIC_ASSERT(sizeof(oop) == sizeof(uintptr_t));
372
373 #ifdef ASSERT
374 void JNIHandleBlock::zap() {
375 // Zap block values
376 _top = 0;
377 for (int index = 0; index < block_size_in_oops; index++) {
378 // NOT using Access here; just bare clobbering to NULL, since the
379 // block no longer contains valid oops.
380 _handles[index] = 0;
381 }
382 }
383 #endif // ASSERT
384
385 JNIHandleBlock* JNIHandleBlock::allocate_block(Thread* thread, AllocFailType alloc_failmode) {
386 assert(thread == NULL || thread == Thread::current(), "sanity check");
387 JNIHandleBlock* block;
388 // Check the thread-local free list for a block so we don't
389 // have to acquire a mutex.
390 if (thread != NULL && thread->free_handle_block() != NULL) {
391 block = thread->free_handle_block();
392 thread->set_free_handle_block(block->_next);
393 }
394 else {
395 // locking with safepoint checking introduces a potential deadlock:
396 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock
397 // - another would hold Threads_lock (jni_AttachCurrentThread) and then
398 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)
399 MutexLocker ml(JNIHandleBlockFreeList_lock,
400 Mutex::_no_safepoint_check_flag);
401 if (_block_free_list == NULL) {
402 // Allocate new block
403 if (alloc_failmode == AllocFailStrategy::RETURN_NULL) {
404 block = new (std::nothrow) JNIHandleBlock();
405 if (block == NULL) {
406 return NULL;
407 }
408 } else {
409 block = new JNIHandleBlock();
410 }
411 _blocks_allocated++;
412 block->zap();
413 #ifndef PRODUCT
414 // Link new block to list of all allocated blocks
415 block->_block_list_link = _block_list;
416 _block_list = block;
417 #endif
418 } else {
419 // Get block from free list
420 block = _block_free_list;
421 _block_free_list = _block_free_list->_next;
422 }
423 }
424 block->_top = 0;
425 block->_next = NULL;
426 block->_pop_frame_link = NULL;
427 block->_planned_capacity = block_size_in_oops;
428 // _last, _free_list & _allocate_before_rebuild initialized in allocate_handle
429 debug_only(block->_last = NULL);
430 debug_only(block->_free_list = NULL);
431 debug_only(block->_allocate_before_rebuild = -1);
432 return block;
433 }
434
435
436 void JNIHandleBlock::release_block(JNIHandleBlock* block, Thread* thread) {
437 assert(thread == NULL || thread == Thread::current(), "sanity check");
438 JNIHandleBlock* pop_frame_link = block->pop_frame_link();
439 // Put returned block at the beginning of the thread-local free list.
440 // Note that if thread == NULL, we use it as an implicit argument that
441 // we _don't_ want the block to be kept on the free_handle_block.
442 // See for instance JavaThread::exit().
443 if (thread != NULL ) {
444 block->zap();
445 JNIHandleBlock* freelist = thread->free_handle_block();
446 block->_pop_frame_link = NULL;
447 thread->set_free_handle_block(block);
448
449 // Add original freelist to end of chain
450 if ( freelist != NULL ) {
451 while ( block->_next != NULL ) block = block->_next;
452 block->_next = freelist;
453 }
454 block = NULL;
455 }
456 if (block != NULL) {
457 // Return blocks to free list
458 // locking with safepoint checking introduces a potential deadlock:
459 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock
460 // - another would hold Threads_lock (jni_AttachCurrentThread) and then
461 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)
462 MutexLocker ml(JNIHandleBlockFreeList_lock,
463 Mutex::_no_safepoint_check_flag);
464 while (block != NULL) {
465 block->zap();
466 JNIHandleBlock* next = block->_next;
467 block->_next = _block_free_list;
468 _block_free_list = block;
469 block = next;
470 }
471 }
472 if (pop_frame_link != NULL) {
473 // As a sanity check we release blocks pointed to by the pop_frame_link.
474 // This should never happen (only if PopLocalFrame is not called the
475 // correct number of times).
476 release_block(pop_frame_link, thread);
477 }
478 }
479
480
481 void JNIHandleBlock::oops_do(OopClosure* f) {
482 JNIHandleBlock* current_chain = this;
483 // Iterate over chain of blocks, followed by chains linked through the
484 // pop frame links.
485 while (current_chain != NULL) {
486 for (JNIHandleBlock* current = current_chain; current != NULL;
487 current = current->_next) {
488 assert(current == current_chain || current->pop_frame_link() == NULL,
489 "only blocks first in chain should have pop frame link set");
490 for (int index = 0; index < current->_top; index++) {
491 uintptr_t* addr = &(current->_handles)[index];
492 uintptr_t value = *addr;
493 // traverse heap pointers only, not deleted handles or free list
494 // pointers
495 if (value != 0 && !is_tagged_free_list(value)) {
496 oop* root = (oop*)addr;
497 f->do_oop(root);
498 }
499 }
500 // the next handle block is valid only if current block is full
501 if (current->_top < block_size_in_oops) {
502 break;
503 }
504 }
505 current_chain = current_chain->pop_frame_link();
506 }
507 }
508
509
510 jobject JNIHandleBlock::allocate_handle(oop obj, AllocFailType alloc_failmode) {
511 assert(Universe::heap()->is_in(obj), "sanity check");
512 if (_top == 0) {
513 // This is the first allocation or the initial block got zapped when
514 // entering a native function. If we have any following blocks they are
515 // not valid anymore.
516 for (JNIHandleBlock* current = _next; current != NULL;
517 current = current->_next) {
518 assert(current->_last == NULL, "only first block should have _last set");
519 assert(current->_free_list == NULL,
520 "only first block should have _free_list set");
521 if (current->_top == 0) {
522 // All blocks after the first clear trailing block are already cleared.
523 #ifdef ASSERT
524 for (current = current->_next; current != NULL; current = current->_next) {
525 assert(current->_top == 0, "trailing blocks must already be cleared");
526 }
527 #endif
528 break;
529 }
530 current->_top = 0;
531 current->zap();
532 }
533 // Clear initial block
534 _free_list = NULL;
535 _allocate_before_rebuild = 0;
536 _last = this;
537 zap();
538 }
539
540 // Try last block
541 if (_last->_top < block_size_in_oops) {
542 oop* handle = (oop*)&(_last->_handles)[_last->_top++];
543 NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, obj);
544 return (jobject) handle;
545 }
546
547 // Try free list
548 if (_free_list != NULL) {
549 oop* handle = (oop*)_free_list;
550 _free_list = (uintptr_t*) untag_free_list(*_free_list);
551 NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, obj);
552 return (jobject) handle;
553 }
554 // Check if unused block follow last
555 if (_last->_next != NULL) {
556 // update last and retry
557 _last = _last->_next;
558 return allocate_handle(obj, alloc_failmode);
559 }
560
561 // No space available, we have to rebuild free list or expand
562 if (_allocate_before_rebuild == 0) {
563 rebuild_free_list(); // updates _allocate_before_rebuild counter
564 } else {
565 // Append new block
566 Thread* thread = Thread::current();
567 Handle obj_handle(thread, obj);
568 // This can block, so we need to preserve obj across call.
569 _last->_next = JNIHandleBlock::allocate_block(thread, alloc_failmode);
570 if (_last->_next == NULL) {
571 return NULL;
572 }
573 _last = _last->_next;
574 _allocate_before_rebuild--;
575 obj = obj_handle();
576 }
577 return allocate_handle(obj, alloc_failmode); // retry
578 }
579
580 void JNIHandleBlock::rebuild_free_list() {
581 assert(_allocate_before_rebuild == 0 && _free_list == NULL, "just checking");
582 int free = 0;
583 int blocks = 0;
584 for (JNIHandleBlock* current = this; current != NULL; current = current->_next) {
585 for (int index = 0; index < current->_top; index++) {
586 uintptr_t* handle = &(current->_handles)[index];
587 if (*handle == 0) {
588 // this handle was cleared out by a delete call, reuse it
589 *handle = _free_list == NULL ? 0 : tag_free_list((uintptr_t)_free_list);
590 _free_list = handle;
591 free++;
592 }
593 }
594 // we should not rebuild free list if there are unused handles at the end
595 assert(current->_top == block_size_in_oops, "just checking");
596 blocks++;
597 }
598 // Heuristic: if more than half of the handles are free we rebuild next time
599 // as well, otherwise we append a corresponding number of new blocks before
600 // attempting a free list rebuild again.
601 int total = blocks * block_size_in_oops;
602 int extra = total - 2*free;
603 if (extra > 0) {
604 // Not as many free handles as we would like - compute number of new blocks to append
605 _allocate_before_rebuild = (extra + block_size_in_oops - 1) / block_size_in_oops;
606 }
607 }
608
609
610 bool JNIHandleBlock::contains(jobject handle) const {
611 return ((jobject)&_handles[0] <= handle && handle<(jobject)&_handles[_top]);
612 }
613
614
615 bool JNIHandleBlock::chain_contains(jobject handle) const {
616 for (JNIHandleBlock* current = (JNIHandleBlock*) this; current != NULL; current = current->_next) {
617 if (current->contains(handle)) {
618 return true;
619 }
620 }
621 return false;
622 }
623
624
625 size_t JNIHandleBlock::length() const {
626 size_t result = 1;
627 for (JNIHandleBlock* current = _next; current != NULL; current = current->_next) {
628 result++;
629 }
630 return result;
631 }
632
633 class CountJNIHandleClosure: public OopClosure {
634 private:
635 int _count;
636 public:
637 CountJNIHandleClosure(): _count(0) {}
638 virtual void do_oop(oop* ooph) { _count++; }
639 virtual void do_oop(narrowOop* unused) { ShouldNotReachHere(); }
640 int count() { return _count; }
641 };
642
643 const size_t JNIHandleBlock::get_number_of_live_handles() {
644 CountJNIHandleClosure counter;
645 oops_do(&counter);
646 return counter.count();
647 }
648
649 // This method is not thread-safe, i.e., must be called while holding a lock on the
650 // structure.
651 size_t JNIHandleBlock::memory_usage() const {
652 return length() * sizeof(JNIHandleBlock);
653 }
654
655
656 #ifndef PRODUCT
657
658 bool JNIHandles::is_local_handle(jobject handle) {
659 return JNIHandleBlock::any_contains(handle);
660 }
661
662 bool JNIHandleBlock::any_contains(jobject handle) {
663 assert(handle != NULL, "precondition");
664 for (JNIHandleBlock* current = _block_list; current != NULL; current = current->_block_list_link) {
665 if (current->contains(handle)) {
666 return true;
667 }
668 }
669 return false;
670 }
671
672 void JNIHandleBlock::print_statistics() {
673 int used_blocks = 0;
674 int free_blocks = 0;
675 int used_handles = 0;
676 int free_handles = 0;
677 JNIHandleBlock* block = _block_list;
678 while (block != NULL) {
679 if (block->_top > 0) {
680 used_blocks++;
681 } else {
682 free_blocks++;
683 }
684 used_handles += block->_top;
685 free_handles += (block_size_in_oops - block->_top);
686 block = block->_block_list_link;
687 }
688 tty->print_cr("JNIHandleBlocks statistics");
689 tty->print_cr("- blocks allocated: %d", used_blocks + free_blocks);
690 tty->print_cr("- blocks in use: %d", used_blocks);
691 tty->print_cr("- blocks free: %d", free_blocks);
692 tty->print_cr("- handles in use: %d", used_handles);
693 tty->print_cr("- handles free: %d", free_handles);
694 }
695
696 #endif