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/oop.inline.hpp"
30 #include "runtime/jniHandles.inline.hpp"
31 #include "runtime/mutexLocker.hpp"
32 #include "runtime/thread.inline.hpp"
33 #include "trace/traceMacros.hpp"
34 #include "utilities/align.hpp"
35 #include "utilities/debug.hpp"
36 #if INCLUDE_ALL_GCS
37 #include "gc/g1/g1BarrierSet.hpp"
38 #endif
39
40 OopStorage* JNIHandles::_global_handles = NULL;
41 OopStorage* JNIHandles::_weak_global_handles = NULL;
42
43
44 jobject JNIHandles::make_local(oop obj) {
45 if (obj == NULL) {
46 return NULL; // ignore null handles
47 } else {
48 Thread* thread = Thread::current();
49 assert(oopDesc::is_oop(obj), "not an oop");
50 assert(!current_thread_in_native(), "must not be in native");
51 return thread->active_handles()->allocate_handle(obj);
52 }
53 }
54
55
56 // optimized versions
57
58 jobject JNIHandles::make_local(Thread* thread, oop obj) {
59 if (obj == NULL) {
60 return NULL; // ignore null handles
61 } else {
62 assert(oopDesc::is_oop(obj), "not an oop");
63 assert(thread->is_Java_thread(), "not a Java thread");
64 assert(!current_thread_in_native(), "must not be in native");
65 return thread->active_handles()->allocate_handle(obj);
66 }
67 }
68
69
70 jobject JNIHandles::make_local(JNIEnv* env, oop obj) {
71 if (obj == NULL) {
72 return NULL; // ignore null handles
73 } else {
74 JavaThread* thread = JavaThread::thread_from_jni_environment(env);
75 assert(oopDesc::is_oop(obj), "not an oop");
76 assert(!current_thread_in_native(), "must not be in native");
77 return thread->active_handles()->allocate_handle(obj);
78 }
79 }
80
81
82 static void report_handle_allocation_failure(AllocFailType alloc_failmode,
83 const char* handle_kind) {
84 if (alloc_failmode == AllocFailStrategy::EXIT_OOM) {
85 // Fake size value, since we don't know the min allocation size here.
86 vm_exit_out_of_memory(sizeof(oop), OOM_MALLOC_ERROR,
87 "Cannot create %s JNI handle", handle_kind);
88 } else {
89 assert(alloc_failmode == AllocFailStrategy::RETURN_NULL, "invariant");
90 }
91 }
92
93 jobject JNIHandles::make_global(Handle obj, AllocFailType alloc_failmode) {
94 assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");
95 assert(!current_thread_in_native(), "must not be in native");
96 jobject res = NULL;
97 if (!obj.is_null()) {
98 // ignore null handles
99 assert(oopDesc::is_oop(obj()), "not an oop");
100 oop* ptr = _global_handles->allocate();
101 // Return NULL on allocation failure.
102 if (ptr != NULL) {
103 *ptr = obj();
104 res = reinterpret_cast<jobject>(ptr);
105 } else {
106 report_handle_allocation_failure(alloc_failmode, "global");
107 }
108 } else {
109 CHECK_UNHANDLED_OOPS_ONLY(Thread::current()->clear_unhandled_oops());
110 }
111
112 return res;
113 }
114
115
116 jobject JNIHandles::make_weak_global(Handle obj, AllocFailType alloc_failmode) {
117 assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");
118 assert(!current_thread_in_native(), "must not be in native");
119 jobject res = NULL;
120 if (!obj.is_null()) {
121 // ignore null handles
122 assert(oopDesc::is_oop(obj()), "not an oop");
123 oop* ptr = _weak_global_handles->allocate();
124 // Return NULL on allocation failure.
125 if (ptr != NULL) {
126 *ptr = obj();
127 char* tptr = reinterpret_cast<char*>(ptr) + weak_tag_value;
128 res = reinterpret_cast<jobject>(tptr);
129 } else {
130 report_handle_allocation_failure(alloc_failmode, "weak global");
131 }
132 } else {
133 CHECK_UNHANDLED_OOPS_ONLY(Thread::current()->clear_unhandled_oops());
134 }
135 return res;
136 }
137
138 // Resolve some erroneous cases to NULL, rather than treating them as
139 // possibly unchecked errors. In particular, deleted handles are
140 // treated as NULL (though a deleted and later reallocated handle
141 // isn't detected).
142 oop JNIHandles::resolve_external_guard(jobject handle) {
143 oop result = NULL;
144 if (handle != NULL) {
145 result = resolve_impl<true /* external_guard */ >(handle);
146 }
147 return result;
148 }
149
150 oop JNIHandles::resolve_jweak(jweak handle) {
151 assert(handle != NULL, "precondition");
152 assert(is_jweak(handle), "precondition");
153 #if INCLUDE_ALL_GCS
154 if (UseZGC) {
155 oop* ref_addr = jweak_ref_addr(handle);
156 return RootAccess<ON_PHANTOM_OOP_REF>::oop_load(ref_addr);
157 }
158 #endif
159
160 oop result = jweak_ref(handle);
161 #if INCLUDE_ALL_GCS
162 if (result != NULL && UseG1GC) {
163 G1BarrierSet::enqueue(result);
164 }
165 #endif // INCLUDE_ALL_GCS
166 return result;
167 }
168
169 bool JNIHandles::is_global_weak_cleared(jweak handle) {
170 assert(handle != NULL, "precondition");
171 assert(is_jweak(handle), "not a weak handle");
172 return jweak_ref(handle) == NULL;
173 }
174
175 void JNIHandles::destroy_global(jobject handle) {
176 if (handle != NULL) {
177 assert(!is_jweak(handle), "wrong method for detroying jweak");
178 jobject_ref(handle) = NULL;
179 _global_handles->release(&jobject_ref(handle));
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 jweak_ref(handle) = NULL;
188 _weak_global_handles->release(&jweak_ref(handle));
189 }
190 }
191
192
193 void JNIHandles::oops_do(OopClosure* f) {
194 _global_handles->oops_do(f);
195 }
196
197
198 void JNIHandles::weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f) {
199 _weak_global_handles->weak_oops_do(is_alive, f);
200 }
201
202
203 void JNIHandles::weak_oops_do(OopClosure* f) {
204 _weak_global_handles->weak_oops_do(f);
205 }
206
207
208 OopStorage* JNIHandles::weak_global_handles() {
209 return _weak_global_handles;
210 }
211
212
213 void JNIHandles::initialize() {
214 _global_handles = new OopStorage("JNI Global",
215 JNIGlobalAlloc_lock,
216 JNIGlobalActive_lock);
217 _weak_global_handles = new OopStorage("JNI Weak",
218 JNIWeakAlloc_lock,
219 JNIWeakActive_lock);
220 }
221
222
223 inline bool is_storage_handle(const OopStorage* storage, const oop* ptr) {
224 return storage->allocation_status(ptr) == OopStorage::ALLOCATED_ENTRY;
225 }
226
227
228 jobjectRefType JNIHandles::handle_type(Thread* thread, jobject handle) {
229 assert(handle != NULL, "precondition");
230 jobjectRefType result = JNIInvalidRefType;
231 if (is_jweak(handle)) {
232 if (is_storage_handle(_weak_global_handles, &jweak_ref(handle))) {
233 result = JNIWeakGlobalRefType;
234 }
235 } else {
236 switch (_global_handles->allocation_status(&jobject_ref(handle))) {
237 case OopStorage::ALLOCATED_ENTRY:
238 result = JNIGlobalRefType;
239 break;
240
241 case OopStorage::UNALLOCATED_ENTRY:
242 break; // Invalid global handle
243
244 case OopStorage::INVALID_ENTRY:
245 // Not in global storage. Might be a local handle.
246 if (is_local_handle(thread, handle) ||
247 (thread->is_Java_thread() &&
248 is_frame_handle((JavaThread*)thread, handle))) {
249 result = JNILocalRefType;
250 }
251 break;
252
253 default:
254 ShouldNotReachHere();
255 }
256 }
257 return result;
258 }
259
260
261 bool JNIHandles::is_local_handle(Thread* thread, jobject handle) {
262 assert(handle != NULL, "precondition");
263 JNIHandleBlock* block = thread->active_handles();
264
265 // Look back past possible native calls to jni_PushLocalFrame.
266 while (block != NULL) {
267 if (block->chain_contains(handle)) {
268 return true;
269 }
270 block = block->pop_frame_link();
271 }
272 return false;
273 }
274
275
276 // Determine if the handle is somewhere in the current thread's stack.
277 // We easily can't isolate any particular stack frame the handle might
278 // come from, so we'll check the whole stack.
279
280 bool JNIHandles::is_frame_handle(JavaThread* thr, jobject handle) {
281 assert(handle != NULL, "precondition");
282 // If there is no java frame, then this must be top level code, such
283 // as the java command executable, in which case, this type of handle
284 // is not permitted.
285 return (thr->has_last_Java_frame() &&
286 (void*)handle < (void*)thr->stack_base() &&
287 (void*)handle >= (void*)thr->last_Java_sp());
288 }
289
290
291 bool JNIHandles::is_global_handle(jobject handle) {
292 assert(handle != NULL, "precondition");
293 return !is_jweak(handle) && is_storage_handle(_global_handles, &jobject_ref(handle));
294 }
295
296
297 bool JNIHandles::is_weak_global_handle(jobject handle) {
298 assert(handle != NULL, "precondition");
299 return is_jweak(handle) && is_storage_handle(_weak_global_handles, &jweak_ref(handle));
300 }
301
302 size_t JNIHandles::global_handle_memory_usage() {
303 return _global_handles->total_memory_usage();
304 }
305
306 size_t JNIHandles::weak_global_handle_memory_usage() {
307 return _weak_global_handles->total_memory_usage();
308 }
309
310
311 // We assume this is called at a safepoint: no lock is needed.
312 void JNIHandles::print_on(outputStream* st) {
313 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
314 assert(_global_handles != NULL && _weak_global_handles != NULL,
315 "JNIHandles not initialized");
316
317 st->print_cr("JNI global refs: " SIZE_FORMAT ", weak refs: " SIZE_FORMAT,
318 _global_handles->allocation_count(),
319 _weak_global_handles->allocation_count());
320 st->cr();
321 st->flush();
322 }
323
324 class VerifyJNIHandles: public OopClosure {
325 public:
326 virtual void do_oop(oop* root) {
327 (*root)->verify();
328 }
329 virtual void do_oop(narrowOop* root) { ShouldNotReachHere(); }
330 };
331
332 void JNIHandles::verify() {
333 VerifyJNIHandles verify_handle;
334
335 oops_do(&verify_handle);
336 if (!UseZGC) {
337 weak_oops_do(&verify_handle);
338 }
339 }
340
341 // This method is implemented here to avoid circular includes between
342 // jniHandles.hpp and thread.hpp.
343 bool JNIHandles::current_thread_in_native() {
344 Thread* thread = Thread::current();
345 return (thread->is_Java_thread() &&
346 JavaThread::current()->thread_state() == _thread_in_native);
347 }
348
349
350 void jni_handles_init() {
351 JNIHandles::initialize();
352 }
353
354
355 int JNIHandleBlock::_blocks_allocated = 0;
356 JNIHandleBlock* JNIHandleBlock::_block_free_list = NULL;
357 #ifndef PRODUCT
358 JNIHandleBlock* JNIHandleBlock::_block_list = NULL;
359 #endif
360
361
362 #ifdef ASSERT
363 void JNIHandleBlock::zap() {
364 // Zap block values
365 _top = 0;
366 for (int index = 0; index < block_size_in_oops; index++) {
367 _handles[index] = NULL;
368 }
369 }
370 #endif // ASSERT
371
372 JNIHandleBlock* JNIHandleBlock::allocate_block(Thread* thread) {
373 assert(thread == NULL || thread == Thread::current(), "sanity check");
374 JNIHandleBlock* block;
375 // Check the thread-local free list for a block so we don't
376 // have to acquire a mutex.
377 if (thread != NULL && thread->free_handle_block() != NULL) {
378 block = thread->free_handle_block();
379 thread->set_free_handle_block(block->_next);
380 }
381 else {
382 // locking with safepoint checking introduces a potential deadlock:
383 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock
384 // - another would hold Threads_lock (jni_AttachCurrentThread) and then
385 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)
386 MutexLockerEx ml(JNIHandleBlockFreeList_lock,
387 Mutex::_no_safepoint_check_flag);
388 if (_block_free_list == NULL) {
389 // Allocate new block
390 block = new JNIHandleBlock();
391 _blocks_allocated++;
392 block->zap();
393 #ifndef PRODUCT
394 // Link new block to list of all allocated blocks
395 block->_block_list_link = _block_list;
396 _block_list = block;
397 #endif
398 } else {
399 // Get block from free list
400 block = _block_free_list;
401 _block_free_list = _block_free_list->_next;
402 }
403 }
404 block->_top = 0;
405 block->_next = NULL;
406 block->_pop_frame_link = NULL;
407 block->_planned_capacity = block_size_in_oops;
408 // _last, _free_list & _allocate_before_rebuild initialized in allocate_handle
409 debug_only(block->_last = NULL);
410 debug_only(block->_free_list = NULL);
411 debug_only(block->_allocate_before_rebuild = -1);
412 return block;
413 }
414
415
416 void JNIHandleBlock::release_block(JNIHandleBlock* block, Thread* thread) {
417 assert(thread == NULL || thread == Thread::current(), "sanity check");
418 JNIHandleBlock* pop_frame_link = block->pop_frame_link();
419 // Put returned block at the beginning of the thread-local free list.
420 // Note that if thread == NULL, we use it as an implicit argument that
421 // we _don't_ want the block to be kept on the free_handle_block.
422 // See for instance JavaThread::exit().
423 if (thread != NULL ) {
424 block->zap();
425 JNIHandleBlock* freelist = thread->free_handle_block();
426 block->_pop_frame_link = NULL;
427 thread->set_free_handle_block(block);
428
429 // Add original freelist to end of chain
430 if ( freelist != NULL ) {
431 while ( block->_next != NULL ) block = block->_next;
432 block->_next = freelist;
433 }
434 block = NULL;
435 }
436 if (block != NULL) {
437 // Return blocks to free list
438 // locking with safepoint checking introduces a potential deadlock:
439 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock
440 // - another would hold Threads_lock (jni_AttachCurrentThread) and then
441 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)
442 MutexLockerEx ml(JNIHandleBlockFreeList_lock,
443 Mutex::_no_safepoint_check_flag);
444 while (block != NULL) {
445 block->zap();
446 JNIHandleBlock* next = block->_next;
447 block->_next = _block_free_list;
448 _block_free_list = block;
449 block = next;
450 }
451 }
452 if (pop_frame_link != NULL) {
453 // As a sanity check we release blocks pointed to by the pop_frame_link.
454 // This should never happen (only if PopLocalFrame is not called the
455 // correct number of times).
456 release_block(pop_frame_link, thread);
457 }
458 }
459
460
461 void JNIHandleBlock::oops_do(OopClosure* f) {
462 JNIHandleBlock* current_chain = this;
463 // Iterate over chain of blocks, followed by chains linked through the
464 // pop frame links.
465 while (current_chain != NULL) {
466 for (JNIHandleBlock* current = current_chain; current != NULL;
467 current = current->_next) {
468 assert(current == current_chain || current->pop_frame_link() == NULL,
469 "only blocks first in chain should have pop frame link set");
470 for (int index = 0; index < current->_top; index++) {
471 oop* root = &(current->_handles)[index];
472 oop value = *root;
473 // traverse heap pointers only, not deleted handles or free list
474 // pointers
475 if (value != NULL && Universe::heap()->is_in_reserved(value)) {
476 f->do_oop(root);
477 }
478 }
479 // the next handle block is valid only if current block is full
480 if (current->_top < block_size_in_oops) {
481 break;
482 }
483 }
484 current_chain = current_chain->pop_frame_link();
485 }
486 }
487
488
489 jobject JNIHandleBlock::allocate_handle(oop obj) {
490 assert(Universe::heap()->is_in_reserved(obj), "sanity check");
491 if (_top == 0) {
492 // This is the first allocation or the initial block got zapped when
493 // entering a native function. If we have any following blocks they are
494 // not valid anymore.
495 for (JNIHandleBlock* current = _next; current != NULL;
496 current = current->_next) {
497 assert(current->_last == NULL, "only first block should have _last set");
498 assert(current->_free_list == NULL,
499 "only first block should have _free_list set");
500 if (current->_top == 0) {
501 // All blocks after the first clear trailing block are already cleared.
502 #ifdef ASSERT
503 for (current = current->_next; current != NULL; current = current->_next) {
504 assert(current->_top == 0, "trailing blocks must already be cleared");
505 }
506 #endif
507 break;
508 }
509 current->_top = 0;
510 current->zap();
511 }
512 // Clear initial block
513 _free_list = NULL;
514 _allocate_before_rebuild = 0;
515 _last = this;
516 zap();
517 }
518
519 // Try last block
520 if (_last->_top < block_size_in_oops) {
521 oop* handle = &(_last->_handles)[_last->_top++];
522 *handle = obj;
523 return (jobject) handle;
524 }
525
526 // Try free list
527 if (_free_list != NULL) {
528 oop* handle = _free_list;
529 _free_list = (oop*) *_free_list;
530 *handle = obj;
531 return (jobject) handle;
532 }
533 // Check if unused block follow last
534 if (_last->_next != NULL) {
535 // update last and retry
536 _last = _last->_next;
537 return allocate_handle(obj);
538 }
539
540 // No space available, we have to rebuild free list or expand
541 if (_allocate_before_rebuild == 0) {
542 rebuild_free_list(); // updates _allocate_before_rebuild counter
543 } else {
544 // Append new block
545 Thread* thread = Thread::current();
546 Handle obj_handle(thread, obj);
547 // This can block, so we need to preserve obj across call.
548 _last->_next = JNIHandleBlock::allocate_block(thread);
549 _last = _last->_next;
550 _allocate_before_rebuild--;
551 obj = obj_handle();
552 }
553 return allocate_handle(obj); // retry
554 }
555
556 void JNIHandleBlock::rebuild_free_list() {
557 assert(_allocate_before_rebuild == 0 && _free_list == NULL, "just checking");
558 int free = 0;
559 int blocks = 0;
560 for (JNIHandleBlock* current = this; current != NULL; current = current->_next) {
561 for (int index = 0; index < current->_top; index++) {
562 oop* handle = &(current->_handles)[index];
563 if (*handle == NULL) {
564 // this handle was cleared out by a delete call, reuse it
565 *handle = (oop) _free_list;
566 _free_list = handle;
567 free++;
568 }
569 }
570 // we should not rebuild free list if there are unused handles at the end
571 assert(current->_top == block_size_in_oops, "just checking");
572 blocks++;
573 }
574 // Heuristic: if more than half of the handles are free we rebuild next time
575 // as well, otherwise we append a corresponding number of new blocks before
576 // attempting a free list rebuild again.
577 int total = blocks * block_size_in_oops;
578 int extra = total - 2*free;
579 if (extra > 0) {
580 // Not as many free handles as we would like - compute number of new blocks to append
581 _allocate_before_rebuild = (extra + block_size_in_oops - 1) / block_size_in_oops;
582 }
583 }
584
585
586 bool JNIHandleBlock::contains(jobject handle) const {
587 return ((jobject)&_handles[0] <= handle && handle<(jobject)&_handles[_top]);
588 }
589
590
591 bool JNIHandleBlock::chain_contains(jobject handle) const {
592 for (JNIHandleBlock* current = (JNIHandleBlock*) this; current != NULL; current = current->_next) {
593 if (current->contains(handle)) {
594 return true;
595 }
596 }
597 return false;
598 }
599
600
601 size_t JNIHandleBlock::length() const {
602 size_t result = 1;
603 for (JNIHandleBlock* current = _next; current != NULL; current = current->_next) {
604 result++;
605 }
606 return result;
607 }
608
609 class CountJNIHandleClosure: public OopClosure {
610 private:
611 int _count;
612 public:
613 CountJNIHandleClosure(): _count(0) {}
614 virtual void do_oop(oop* ooph) { _count++; }
615 virtual void do_oop(narrowOop* unused) { ShouldNotReachHere(); }
616 int count() { return _count; }
617 };
618
619 const size_t JNIHandleBlock::get_number_of_live_handles() {
620 CountJNIHandleClosure counter;
621 oops_do(&counter);
622 return counter.count();
623 }
624
625 // This method is not thread-safe, i.e., must be called while holding a lock on the
626 // structure.
627 size_t JNIHandleBlock::memory_usage() const {
628 return length() * sizeof(JNIHandleBlock);
629 }
630
631
632 #ifndef PRODUCT
633
634 bool JNIHandles::is_local_handle(jobject handle) {
635 return JNIHandleBlock::any_contains(handle);
636 }
637
638 bool JNIHandleBlock::any_contains(jobject handle) {
639 assert(handle != NULL, "precondition");
640 for (JNIHandleBlock* current = _block_list; current != NULL; current = current->_block_list_link) {
641 if (current->contains(handle)) {
642 return true;
643 }
644 }
645 return false;
646 }
647
648 void JNIHandleBlock::print_statistics() {
649 int used_blocks = 0;
650 int free_blocks = 0;
651 int used_handles = 0;
652 int free_handles = 0;
653 JNIHandleBlock* block = _block_list;
654 while (block != NULL) {
655 if (block->_top > 0) {
656 used_blocks++;
657 } else {
658 free_blocks++;
659 }
660 used_handles += block->_top;
661 free_handles += (block_size_in_oops - block->_top);
662 block = block->_block_list_link;
663 }
664 tty->print_cr("JNIHandleBlocks statistics");
665 tty->print_cr("- blocks allocated: %d", used_blocks + free_blocks);
666 tty->print_cr("- blocks in use: %d", used_blocks);
667 tty->print_cr("- blocks free: %d", free_blocks);
668 tty->print_cr("- handles in use: %d", used_handles);
669 tty->print_cr("- handles free: %d", free_handles);
670 }
671
672 #endif