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