1 /*
2 * Copyright (c) 1998, 2018, 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 "logging/log.hpp"
28 #include "memory/iterator.hpp"
29 #include "oops/access.inline.hpp"
30 #include "oops/oop.inline.hpp"
31 #include "runtime/handles.inline.hpp"
32 #include "runtime/jniHandles.inline.hpp"
33 #include "runtime/mutexLocker.hpp"
34 #include "runtime/thread.inline.hpp"
35 #include "utilities/align.hpp"
36 #include "utilities/debug.hpp"
37
38 OopStorage* JNIHandles::_global_handles = NULL;
39 OopStorage* JNIHandles::_weak_global_handles = NULL;
40
41 OopStorage* JNIHandles::global_handles() {
42 assert(_global_handles != NULL, "Uninitialized JNI global handles");
43 return _global_handles;
44 }
45
46 OopStorage* JNIHandles::weak_global_handles() {
47 assert(_weak_global_handles != NULL, "Uninitialized JNI weak global handles");
48 return _weak_global_handles;
49 }
50
51
52 jobject JNIHandles::make_local(oop obj) {
53 if (obj == NULL) {
54 return NULL; // ignore null handles
55 } else {
56 Thread* thread = Thread::current();
57 assert(oopDesc::is_oop(obj), "not an oop");
58 assert(!current_thread_in_native(), "must not be in native");
59 return thread->active_handles()->allocate_handle(obj);
60 }
61 }
62
63
64 // optimized versions
65
66 jobject JNIHandles::make_local(Thread* thread, oop obj) {
67 if (obj == NULL) {
68 return NULL; // ignore null handles
69 } else {
70 assert(oopDesc::is_oop(obj), "not an oop");
71 assert(thread->is_Java_thread(), "not a Java thread");
72 assert(!current_thread_in_native(), "must not be in native");
73 return thread->active_handles()->allocate_handle(obj);
74 }
75 }
76
77
78 jobject JNIHandles::make_local(JNIEnv* env, oop obj) {
79 if (obj == NULL) {
80 return NULL; // ignore null handles
81 } else {
82 JavaThread* thread = JavaThread::thread_from_jni_environment(env);
83 assert(oopDesc::is_oop(obj), "not an oop");
84 assert(!current_thread_in_native(), "must not be in native");
85 return thread->active_handles()->allocate_handle(obj);
86 }
87 }
88
89
90 static void report_handle_allocation_failure(AllocFailType alloc_failmode,
91 const char* handle_kind) {
92 if (alloc_failmode == AllocFailStrategy::EXIT_OOM) {
93 // Fake size value, since we don't know the min allocation size here.
94 vm_exit_out_of_memory(sizeof(oop), OOM_MALLOC_ERROR,
95 "Cannot create %s JNI handle", handle_kind);
96 } else {
97 assert(alloc_failmode == AllocFailStrategy::RETURN_NULL, "invariant");
98 }
99 }
100
101 jobject JNIHandles::make_global(Handle obj, AllocFailType alloc_failmode) {
102 assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");
103 assert(!current_thread_in_native(), "must not be in native");
104 jobject res = NULL;
105 if (!obj.is_null()) {
106 // ignore null handles
107 assert(oopDesc::is_oop(obj()), "not an oop");
108 oop* ptr = global_handles()->allocate();
109 // Return NULL on allocation failure.
110 if (ptr != NULL) {
111 assert(*ptr == NULL, "invariant");
112 RootAccess<IN_CONCURRENT_ROOT>::oop_store(ptr, obj());
113 res = reinterpret_cast<jobject>(ptr);
114 } else {
115 report_handle_allocation_failure(alloc_failmode, "global");
116 }
117 } else {
118 CHECK_UNHANDLED_OOPS_ONLY(Thread::current()->clear_unhandled_oops());
119 }
120
121 return res;
122 }
123
124
125 jobject JNIHandles::make_weak_global(Handle obj, AllocFailType alloc_failmode) {
126 assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");
127 assert(!current_thread_in_native(), "must not be in native");
128 jobject res = NULL;
129 if (!obj.is_null()) {
130 // ignore null handles
131 assert(oopDesc::is_oop(obj()), "not an oop");
132 oop* ptr = weak_global_handles()->allocate();
133 // Return NULL on allocation failure.
134 if (ptr != NULL) {
135 assert(*ptr == NULL, "invariant");
136 RootAccess<ON_PHANTOM_OOP_REF>::oop_store(ptr, obj());
137 char* tptr = reinterpret_cast<char*>(ptr) + weak_tag_value;
138 res = reinterpret_cast<jobject>(tptr);
139 } else {
140 report_handle_allocation_failure(alloc_failmode, "weak global");
141 }
142 } else {
143 CHECK_UNHANDLED_OOPS_ONLY(Thread::current()->clear_unhandled_oops());
144 }
145 return res;
146 }
147
148 // Resolve some erroneous cases to NULL, rather than treating them as
149 // possibly unchecked errors. In particular, deleted handles are
150 // treated as NULL (though a deleted and later reallocated handle
151 // isn't detected).
152 oop JNIHandles::resolve_external_guard(jobject handle) {
153 oop result = NULL;
154 if (handle != NULL) {
155 result = resolve_impl<true /* external_guard */ >(handle);
156 }
157 return result;
158 }
159
160 oop JNIHandles::resolve_jweak(jweak handle) {
161 assert(handle != NULL, "precondition");
162 assert(is_jweak(handle), "precondition");
163 return RootAccess<ON_PHANTOM_OOP_REF>::oop_load(jweak_ptr(handle));
164 }
165
166 bool JNIHandles::is_global_weak_cleared(jweak handle) {
167 assert(handle != NULL, "precondition");
168 assert(is_jweak(handle), "not a weak handle");
169 oop* oop_ptr = jweak_ptr(handle);
170 oop value = RootAccess<ON_PHANTOM_OOP_REF | AS_NO_KEEPALIVE>::oop_load(oop_ptr);
171 return value == NULL;
172 }
173
174 void JNIHandles::destroy_global(jobject handle) {
175 if (handle != NULL) {
176 assert(!is_jweak(handle), "wrong method for detroying jweak");
177 oop* oop_ptr = jobject_ptr(handle);
178 RootAccess<IN_CONCURRENT_ROOT>::oop_store(oop_ptr, (oop)NULL);
179 global_handles()->release(oop_ptr);
180 }
181 }
182
183
184 void JNIHandles::destroy_weak_global(jobject handle) {
185 if (handle != NULL) {
186 assert(is_jweak(handle), "JNI handle not jweak");
187 oop* oop_ptr = jweak_ptr(handle);
188 RootAccess<ON_PHANTOM_OOP_REF>::oop_store(oop_ptr, (oop)NULL);
189 weak_global_handles()->release(oop_ptr);
190 }
191 }
192
193
194 void JNIHandles::oops_do(OopClosure* f) {
195 global_handles()->oops_do(f);
196 }
197
198
199 void JNIHandles::weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f) {
200 weak_global_handles()->weak_oops_do(is_alive, f);
201 }
202
203
204 void JNIHandles::weak_oops_do(OopClosure* f) {
205 weak_global_handles()->weak_oops_do(f);
206 }
207
208
209 void JNIHandles::initialize() {
210 _global_handles = new OopStorage("JNI Global",
211 JNIGlobalAlloc_lock,
212 JNIGlobalActive_lock);
213 _weak_global_handles = new OopStorage("JNI Weak",
214 JNIWeakAlloc_lock,
215 JNIWeakActive_lock);
216 }
217
218
219 inline bool is_storage_handle(const OopStorage* storage, const oop* ptr) {
220 return storage->allocation_status(ptr) == OopStorage::ALLOCATED_ENTRY;
221 }
222
223
224 jobjectRefType JNIHandles::handle_type(Thread* thread, jobject handle) {
225 assert(handle != NULL, "precondition");
226 jobjectRefType result = JNIInvalidRefType;
227 if (is_jweak(handle)) {
228 if (is_storage_handle(weak_global_handles(), jweak_ptr(handle))) {
229 result = JNIWeakGlobalRefType;
230 }
231 } else {
232 switch (global_handles()->allocation_status(jobject_ptr(handle))) {
233 case OopStorage::ALLOCATED_ENTRY:
234 result = JNIGlobalRefType;
235 break;
236
237 case OopStorage::UNALLOCATED_ENTRY:
238 break; // Invalid global handle
239
240 case OopStorage::INVALID_ENTRY:
241 // Not in global storage. Might be a local handle.
242 if (is_local_handle(thread, handle) ||
243 (thread->is_Java_thread() &&
244 is_frame_handle((JavaThread*)thread, handle))) {
245 result = JNILocalRefType;
246 }
247 break;
248
249 default:
250 ShouldNotReachHere();
251 }
252 }
253 return result;
254 }
255
256
257 bool JNIHandles::is_local_handle(Thread* thread, jobject handle) {
258 assert(handle != NULL, "precondition");
259 JNIHandleBlock* block = thread->active_handles();
260
261 // Look back past possible native calls to jni_PushLocalFrame.
262 while (block != NULL) {
263 if (block->chain_contains(handle)) {
264 return true;
265 }
266 block = block->pop_frame_link();
267 }
268 return false;
269 }
270
271
272 // Determine if the handle is somewhere in the current thread's stack.
273 // We easily can't isolate any particular stack frame the handle might
274 // come from, so we'll check the whole stack.
275
276 bool JNIHandles::is_frame_handle(JavaThread* thr, jobject handle) {
277 assert(handle != NULL, "precondition");
278 // If there is no java frame, then this must be top level code, such
279 // as the java command executable, in which case, this type of handle
280 // is not permitted.
281 return (thr->has_last_Java_frame() &&
282 (void*)handle < (void*)thr->stack_base() &&
283 (void*)handle >= (void*)thr->last_Java_sp());
284 }
285
286
287 bool JNIHandles::is_global_handle(jobject handle) {
288 assert(handle != NULL, "precondition");
289 return !is_jweak(handle) && is_storage_handle(global_handles(), jobject_ptr(handle));
290 }
291
292
293 bool JNIHandles::is_weak_global_handle(jobject handle) {
294 assert(handle != NULL, "precondition");
295 return is_jweak(handle) && is_storage_handle(weak_global_handles(), jweak_ptr(handle));
296 }
297
298 size_t JNIHandles::global_handle_memory_usage() {
299 return global_handles()->total_memory_usage();
300 }
301
302 size_t JNIHandles::weak_global_handle_memory_usage() {
303 return weak_global_handles()->total_memory_usage();
304 }
305
306
307 // We assume this is called at a safepoint: no lock is needed.
308 void JNIHandles::print_on(outputStream* st) {
309 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
310
311 st->print_cr("JNI global refs: " SIZE_FORMAT ", weak refs: " SIZE_FORMAT,
312 global_handles()->allocation_count(),
313 weak_global_handles()->allocation_count());
314 st->cr();
315 st->flush();
316 }
317
318 class VerifyJNIHandles: public OopClosure {
319 public:
320 virtual void do_oop(oop* root) {
321 (*root)->verify();
322 }
323 virtual void do_oop(narrowOop* root) { ShouldNotReachHere(); }
324 };
325
326 void JNIHandles::verify() {
327 VerifyJNIHandles verify_handle;
328
329 oops_do(&verify_handle);
330 weak_oops_do(&verify_handle);
331 }
332
333 // This method is implemented here to avoid circular includes between
334 // jniHandles.hpp and thread.hpp.
335 bool JNIHandles::current_thread_in_native() {
336 Thread* thread = Thread::current();
337 return (thread->is_Java_thread() &&
338 JavaThread::current()->thread_state() == _thread_in_native);
339 }
340
341
342 void jni_handles_init() {
343 JNIHandles::initialize();
344 }
345
346
347 int JNIHandleBlock::_blocks_allocated = 0;
348 JNIHandleBlock* JNIHandleBlock::_block_free_list = NULL;
349 #ifndef PRODUCT
350 JNIHandleBlock* JNIHandleBlock::_block_list = NULL;
351 #endif
352
353
354 #ifdef ASSERT
355 void JNIHandleBlock::zap() {
356 // Zap block values
357 _top = 0;
358 for (int index = 0; index < block_size_in_oops; index++) {
359 // NOT using Access here; just bare clobbering to NULL, since the
360 // block no longer contains valid oops.
361 _handles[index] = NULL;
362 }
363 }
364 #endif // ASSERT
365
366 JNIHandleBlock* JNIHandleBlock::allocate_block(Thread* thread) {
367 assert(thread == NULL || thread == Thread::current(), "sanity check");
368 JNIHandleBlock* block;
369 // Check the thread-local free list for a block so we don't
370 // have to acquire a mutex.
371 if (thread != NULL && thread->free_handle_block() != NULL) {
372 block = thread->free_handle_block();
373 thread->set_free_handle_block(block->_next);
374 }
375 else {
376 // locking with safepoint checking introduces a potential deadlock:
377 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock
378 // - another would hold Threads_lock (jni_AttachCurrentThread) and then
379 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)
380 MutexLockerEx ml(JNIHandleBlockFreeList_lock,
381 Mutex::_no_safepoint_check_flag);
382 if (_block_free_list == NULL) {
383 // Allocate new block
384 block = new JNIHandleBlock();
385 _blocks_allocated++;
386 block->zap();
387 #ifndef PRODUCT
388 // Link new block to list of all allocated blocks
389 block->_block_list_link = _block_list;
390 _block_list = block;
391 #endif
392 } else {
393 // Get block from free list
394 block = _block_free_list;
395 _block_free_list = _block_free_list->_next;
396 }
397 }
398 block->_top = 0;
399 block->_next = NULL;
400 block->_pop_frame_link = NULL;
401 block->_planned_capacity = block_size_in_oops;
402 // _last, _free_list & _allocate_before_rebuild initialized in allocate_handle
403 debug_only(block->_last = NULL);
404 debug_only(block->_free_list = NULL);
405 debug_only(block->_allocate_before_rebuild = -1);
406 return block;
407 }
408
409
410 void JNIHandleBlock::release_block(JNIHandleBlock* block, Thread* thread) {
411 assert(thread == NULL || thread == Thread::current(), "sanity check");
412 JNIHandleBlock* pop_frame_link = block->pop_frame_link();
413 // Put returned block at the beginning of the thread-local free list.
414 // Note that if thread == NULL, we use it as an implicit argument that
415 // we _don't_ want the block to be kept on the free_handle_block.
416 // See for instance JavaThread::exit().
417 if (thread != NULL ) {
418 block->zap();
419 JNIHandleBlock* freelist = thread->free_handle_block();
420 block->_pop_frame_link = NULL;
421 thread->set_free_handle_block(block);
422
423 // Add original freelist to end of chain
424 if ( freelist != NULL ) {
425 while ( block->_next != NULL ) block = block->_next;
426 block->_next = freelist;
427 }
428 block = NULL;
429 }
430 if (block != NULL) {
431 // Return blocks to free list
432 // locking with safepoint checking introduces a potential deadlock:
433 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock
434 // - another would hold Threads_lock (jni_AttachCurrentThread) and then
435 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)
436 MutexLockerEx ml(JNIHandleBlockFreeList_lock,
437 Mutex::_no_safepoint_check_flag);
438 while (block != NULL) {
439 block->zap();
440 JNIHandleBlock* next = block->_next;
441 block->_next = _block_free_list;
442 _block_free_list = block;
443 block = next;
444 }
445 }
446 if (pop_frame_link != NULL) {
447 // As a sanity check we release blocks pointed to by the pop_frame_link.
448 // This should never happen (only if PopLocalFrame is not called the
449 // correct number of times).
450 release_block(pop_frame_link, thread);
451 }
452 }
453
454
455 void JNIHandleBlock::oops_do(OopClosure* f) {
456 JNIHandleBlock* current_chain = this;
457 // Iterate over chain of blocks, followed by chains linked through the
458 // pop frame links.
459 while (current_chain != NULL) {
460 for (JNIHandleBlock* current = current_chain; current != NULL;
461 current = current->_next) {
462 assert(current == current_chain || current->pop_frame_link() == NULL,
463 "only blocks first in chain should have pop frame link set");
464 for (int index = 0; index < current->_top; index++) {
465 oop* root = &(current->_handles)[index];
466 oop value = *root;
467 // traverse heap pointers only, not deleted handles or free list
468 // pointers
469 if (value != NULL && Universe::heap()->is_in_reserved(value)) {
470 f->do_oop(root);
471 }
472 }
473 // the next handle block is valid only if current block is full
474 if (current->_top < block_size_in_oops) {
475 break;
476 }
477 }
478 current_chain = current_chain->pop_frame_link();
479 }
480 }
481
482
483 jobject JNIHandleBlock::allocate_handle(oop obj) {
484 assert(Universe::heap()->is_in_reserved(obj), "sanity check");
485 if (_top == 0) {
486 // This is the first allocation or the initial block got zapped when
487 // entering a native function. If we have any following blocks they are
488 // not valid anymore.
489 for (JNIHandleBlock* current = _next; current != NULL;
490 current = current->_next) {
491 assert(current->_last == NULL, "only first block should have _last set");
492 assert(current->_free_list == NULL,
493 "only first block should have _free_list set");
494 if (current->_top == 0) {
495 // All blocks after the first clear trailing block are already cleared.
496 #ifdef ASSERT
497 for (current = current->_next; current != NULL; current = current->_next) {
498 assert(current->_top == 0, "trailing blocks must already be cleared");
499 }
500 #endif
501 break;
502 }
503 current->_top = 0;
504 current->zap();
505 }
506 // Clear initial block
507 _free_list = NULL;
508 _allocate_before_rebuild = 0;
509 _last = this;
510 zap();
511 }
512
513 // Try last block
514 if (_last->_top < block_size_in_oops) {
515 oop* handle = &(_last->_handles)[_last->_top++];
516 RootAccess<AS_DEST_NOT_INITIALIZED>::oop_store(handle, obj);
517 return (jobject) handle;
518 }
519
520 // Try free list
521 if (_free_list != NULL) {
522 oop* handle = _free_list;
523 _free_list = (oop*) *_free_list;
524 RootAccess<AS_DEST_NOT_INITIALIZED>::oop_store(handle, obj);
525 return (jobject) handle;
526 }
527 // Check if unused block follow last
528 if (_last->_next != NULL) {
529 // update last and retry
530 _last = _last->_next;
531 return allocate_handle(obj);
532 }
533
534 // No space available, we have to rebuild free list or expand
535 if (_allocate_before_rebuild == 0) {
536 rebuild_free_list(); // updates _allocate_before_rebuild counter
537 } else {
538 // Append new block
539 Thread* thread = Thread::current();
540 Handle obj_handle(thread, obj);
541 // This can block, so we need to preserve obj across call.
542 _last->_next = JNIHandleBlock::allocate_block(thread);
543 _last = _last->_next;
544 _allocate_before_rebuild--;
545 obj = obj_handle();
546 }
547 return allocate_handle(obj); // retry
548 }
549
550 void JNIHandleBlock::rebuild_free_list() {
551 assert(_allocate_before_rebuild == 0 && _free_list == NULL, "just checking");
552 int free = 0;
553 int blocks = 0;
554 for (JNIHandleBlock* current = this; current != NULL; current = current->_next) {
555 for (int index = 0; index < current->_top; index++) {
556 oop* handle = &(current->_handles)[index];
557 if (*handle == NULL) {
558 // this handle was cleared out by a delete call, reuse it
559 *handle = (oop) _free_list;
560 _free_list = handle;
561 free++;
562 }
563 }
564 // we should not rebuild free list if there are unused handles at the end
565 assert(current->_top == block_size_in_oops, "just checking");
566 blocks++;
567 }
568 // Heuristic: if more than half of the handles are free we rebuild next time
569 // as well, otherwise we append a corresponding number of new blocks before
570 // attempting a free list rebuild again.
571 int total = blocks * block_size_in_oops;
572 int extra = total - 2*free;
573 if (extra > 0) {
574 // Not as many free handles as we would like - compute number of new blocks to append
575 _allocate_before_rebuild = (extra + block_size_in_oops - 1) / block_size_in_oops;
576 }
577 }
578
579
580 bool JNIHandleBlock::contains(jobject handle) const {
581 return ((jobject)&_handles[0] <= handle && handle<(jobject)&_handles[_top]);
582 }
583
584
585 bool JNIHandleBlock::chain_contains(jobject handle) const {
586 for (JNIHandleBlock* current = (JNIHandleBlock*) this; current != NULL; current = current->_next) {
587 if (current->contains(handle)) {
588 return true;
589 }
590 }
591 return false;
592 }
593
594
595 size_t JNIHandleBlock::length() const {
596 size_t result = 1;
597 for (JNIHandleBlock* current = _next; current != NULL; current = current->_next) {
598 result++;
599 }
600 return result;
601 }
602
603 class CountJNIHandleClosure: public OopClosure {
604 private:
605 int _count;
606 public:
607 CountJNIHandleClosure(): _count(0) {}
608 virtual void do_oop(oop* ooph) { _count++; }
609 virtual void do_oop(narrowOop* unused) { ShouldNotReachHere(); }
610 int count() { return _count; }
611 };
612
613 const size_t JNIHandleBlock::get_number_of_live_handles() {
614 CountJNIHandleClosure counter;
615 oops_do(&counter);
616 return counter.count();
617 }
618
619 // This method is not thread-safe, i.e., must be called while holding a lock on the
620 // structure.
621 size_t JNIHandleBlock::memory_usage() const {
622 return length() * sizeof(JNIHandleBlock);
623 }
624
625
626 #ifndef PRODUCT
627
628 bool JNIHandles::is_local_handle(jobject handle) {
629 return JNIHandleBlock::any_contains(handle);
630 }
631
632 bool JNIHandleBlock::any_contains(jobject handle) {
633 assert(handle != NULL, "precondition");
634 for (JNIHandleBlock* current = _block_list; current != NULL; current = current->_block_list_link) {
635 if (current->contains(handle)) {
636 return true;
637 }
638 }
639 return false;
640 }
641
642 void JNIHandleBlock::print_statistics() {
643 int used_blocks = 0;
644 int free_blocks = 0;
645 int used_handles = 0;
646 int free_handles = 0;
647 JNIHandleBlock* block = _block_list;
648 while (block != NULL) {
649 if (block->_top > 0) {
650 used_blocks++;
651 } else {
652 free_blocks++;
653 }
654 used_handles += block->_top;
655 free_handles += (block_size_in_oops - block->_top);
656 block = block->_block_list_link;
657 }
658 tty->print_cr("JNIHandleBlocks statistics");
659 tty->print_cr("- blocks allocated: %d", used_blocks + free_blocks);
660 tty->print_cr("- blocks in use: %d", used_blocks);
661 tty->print_cr("- blocks free: %d", free_blocks);
662 tty->print_cr("- handles in use: %d", used_handles);
663 tty->print_cr("- handles free: %d", free_handles);
664 }
665
666 #endif