1 /*
2 * Copyright (c) 1998, 2019, 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.inline.hpp"
36 #include "runtime/thread.inline.hpp"
37 #include "utilities/align.hpp"
38 #include "utilities/debug.hpp"
39
40 static OopStorage* global_handles() {
41 return OopStorageSet::jni_global();
42 }
43
44 static OopStorage* weak_global_handles() {
45 return OopStorageSet::jni_weak();
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 = global_handles();
54 JNIHandles::_weak_global_handles = weak_global_handles();
55 }
56
57
58 jobject JNIHandles::make_local(oop obj) {
59 if (obj == NULL) {
60 return NULL; // ignore null handles
61 } else {
62 Thread* thread = Thread::current();
63 assert(oopDesc::is_oop(obj), "not an oop");
64 assert(!current_thread_in_native(), "must not be in native");
65 return thread->active_handles()->allocate_handle(obj);
66 }
67 }
68
69
70 // optimized versions
71
72 jobject JNIHandles::make_local(Thread* thread, oop obj) {
73 if (obj == NULL) {
74 return NULL; // ignore null handles
75 } else {
76 assert(oopDesc::is_oop(obj), "not an oop");
77 assert(thread->is_Java_thread(), "not a Java thread");
78 assert(!current_thread_in_native(), "must not be in native");
79 return thread->active_handles()->allocate_handle(obj);
80 }
81 }
82
83
84 jobject JNIHandles::make_local(JNIEnv* env, oop obj) {
85 if (obj == NULL) {
86 return NULL; // ignore null handles
87 } else {
88 JavaThread* thread = JavaThread::thread_from_jni_environment(env);
89 assert(oopDesc::is_oop(obj), "not an oop");
90 assert(!current_thread_in_native(), "must not be in native");
91 return thread->active_handles()->allocate_handle(obj);
92 }
93 }
94
95
96 static void report_handle_allocation_failure(AllocFailType alloc_failmode,
97 const char* handle_kind) {
98 if (alloc_failmode == AllocFailStrategy::EXIT_OOM) {
99 // Fake size value, since we don't know the min allocation size here.
100 vm_exit_out_of_memory(sizeof(oop), OOM_MALLOC_ERROR,
101 "Cannot create %s JNI handle", handle_kind);
102 } else {
103 assert(alloc_failmode == AllocFailStrategy::RETURN_NULL, "invariant");
104 }
105 }
106
107 jobject JNIHandles::make_global(Handle obj, AllocFailType alloc_failmode) {
108 assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");
109 assert(!current_thread_in_native(), "must not be in native");
110 jobject res = NULL;
111 if (!obj.is_null()) {
112 // ignore null handles
113 assert(oopDesc::is_oop(obj()), "not an oop");
114 oop* ptr = global_handles()->allocate();
115 // Return NULL on allocation failure.
116 if (ptr != NULL) {
117 assert(*ptr == NULL, "invariant");
118 NativeAccess<>::oop_store(ptr, obj());
119 res = reinterpret_cast<jobject>(ptr);
120 } else {
121 report_handle_allocation_failure(alloc_failmode, "global");
122 }
123 }
124
125 return res;
126 }
127
128
129 jobject JNIHandles::make_weak_global(Handle obj, AllocFailType alloc_failmode) {
130 assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");
131 assert(!current_thread_in_native(), "must not be in native");
132 jobject res = NULL;
133 if (!obj.is_null()) {
134 // ignore null handles
135 assert(oopDesc::is_oop(obj()), "not an oop");
136 oop* ptr = weak_global_handles()->allocate();
137 // Return NULL on allocation failure.
138 if (ptr != NULL) {
139 assert(*ptr == NULL, "invariant");
140 NativeAccess<ON_PHANTOM_OOP_REF>::oop_store(ptr, obj());
141 char* tptr = reinterpret_cast<char*>(ptr) + weak_tag_value;
142 res = reinterpret_cast<jobject>(tptr);
143 } else {
144 report_handle_allocation_failure(alloc_failmode, "weak global");
145 }
146 }
147 return res;
148 }
149
150 // Resolve some erroneous cases to NULL, rather than treating them as
151 // possibly unchecked errors. In particular, deleted handles are
152 // treated as NULL (though a deleted and later reallocated handle
153 // isn't detected).
154 oop JNIHandles::resolve_external_guard(jobject handle) {
155 oop result = NULL;
156 if (handle != NULL) {
157 result = resolve_impl<DECORATORS_NONE, true /* external_guard */>(handle);
158 }
159 return result;
160 }
161
162 bool JNIHandles::is_global_weak_cleared(jweak handle) {
163 assert(handle != NULL, "precondition");
164 assert(is_jweak(handle), "not a weak handle");
165 oop* oop_ptr = jweak_ptr(handle);
166 oop value = NativeAccess<ON_PHANTOM_OOP_REF | AS_NO_KEEPALIVE>::oop_load(oop_ptr);
167 return value == NULL;
168 }
169
170 void JNIHandles::destroy_global(jobject handle) {
171 if (handle != NULL) {
172 assert(!is_jweak(handle), "wrong method for detroying jweak");
173 oop* oop_ptr = jobject_ptr(handle);
174 NativeAccess<>::oop_store(oop_ptr, (oop)NULL);
175 global_handles()->release(oop_ptr);
176 }
177 }
178
179
180 void JNIHandles::destroy_weak_global(jobject handle) {
181 if (handle != NULL) {
182 assert(is_jweak(handle), "JNI handle not jweak");
183 oop* oop_ptr = jweak_ptr(handle);
184 NativeAccess<ON_PHANTOM_OOP_REF>::oop_store(oop_ptr, (oop)NULL);
185 weak_global_handles()->release(oop_ptr);
186 }
187 }
188
189
190 void JNIHandles::oops_do(OopClosure* f) {
191 global_handles()->oops_do(f);
192 }
193
194
195 void JNIHandles::weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f) {
196 weak_global_handles()->weak_oops_do(is_alive, f);
197 }
198
199
200 void JNIHandles::weak_oops_do(OopClosure* f) {
201 weak_global_handles()->weak_oops_do(f);
202 }
203
204
205 inline bool is_storage_handle(const OopStorage* storage, const oop* ptr) {
206 return storage->allocation_status(ptr) == OopStorage::ALLOCATED_ENTRY;
207 }
208
209
210 jobjectRefType JNIHandles::handle_type(Thread* thread, jobject handle) {
211 assert(handle != NULL, "precondition");
212 jobjectRefType result = JNIInvalidRefType;
213 if (is_jweak(handle)) {
214 if (is_storage_handle(weak_global_handles(), jweak_ptr(handle))) {
215 result = JNIWeakGlobalRefType;
216 }
217 } else {
218 switch (global_handles()->allocation_status(jobject_ptr(handle))) {
219 case OopStorage::ALLOCATED_ENTRY:
220 result = JNIGlobalRefType;
221 break;
222
223 case OopStorage::UNALLOCATED_ENTRY:
224 break; // Invalid global handle
225
226 case OopStorage::INVALID_ENTRY:
227 // Not in global storage. Might be a local handle.
228 if (is_local_handle(thread, handle) ||
229 (thread->is_Java_thread() &&
230 is_frame_handle((JavaThread*)thread, handle))) {
231 result = JNILocalRefType;
232 }
233 break;
234
235 default:
236 ShouldNotReachHere();
237 }
238 }
239 return result;
240 }
241
242
243 bool JNIHandles::is_local_handle(Thread* thread, jobject handle) {
244 assert(handle != NULL, "precondition");
245 JNIHandleBlock* block = thread->active_handles();
246
247 // Look back past possible native calls to jni_PushLocalFrame.
248 while (block != NULL) {
249 if (block->chain_contains(handle)) {
250 return true;
251 }
252 block = block->pop_frame_link();
253 }
254 return false;
255 }
256
257
258 // Determine if the handle is somewhere in the current thread's stack.
259 // We easily can't isolate any particular stack frame the handle might
260 // come from, so we'll check the whole stack.
261
262 bool JNIHandles::is_frame_handle(JavaThread* thr, jobject handle) {
263 assert(handle != NULL, "precondition");
264 // If there is no java frame, then this must be top level code, such
265 // as the java command executable, in which case, this type of handle
266 // is not permitted.
267 return (thr->has_last_Java_frame() &&
268 (void*)handle < (void*)thr->stack_base() &&
269 (void*)handle >= (void*)thr->last_Java_sp());
270 }
271
272
273 bool JNIHandles::is_global_handle(jobject handle) {
274 assert(handle != NULL, "precondition");
275 return !is_jweak(handle) && is_storage_handle(global_handles(), jobject_ptr(handle));
276 }
277
278
279 bool JNIHandles::is_weak_global_handle(jobject handle) {
280 assert(handle != NULL, "precondition");
281 return is_jweak(handle) && is_storage_handle(weak_global_handles(), jweak_ptr(handle));
282 }
283
284 size_t JNIHandles::global_handle_memory_usage() {
285 return global_handles()->total_memory_usage();
286 }
287
288 size_t JNIHandles::weak_global_handle_memory_usage() {
289 return weak_global_handles()->total_memory_usage();
290 }
291
292
293 // We assume this is called at a safepoint: no lock is needed.
294 void JNIHandles::print_on(outputStream* st) {
295 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
296
297 st->print_cr("JNI global refs: " SIZE_FORMAT ", weak refs: " SIZE_FORMAT,
298 global_handles()->allocation_count(),
299 weak_global_handles()->allocation_count());
300 st->cr();
301 st->flush();
302 }
303
304 void JNIHandles::print() { print_on(tty); }
305
306 class VerifyJNIHandles: public OopClosure {
307 public:
308 virtual void do_oop(oop* root) {
309 guarantee(oopDesc::is_oop_or_null(RawAccess<>::oop_load(root)), "Invalid oop");
310 }
311 virtual void do_oop(narrowOop* root) { ShouldNotReachHere(); }
312 };
313
314 void JNIHandles::verify() {
315 VerifyJNIHandles verify_handle;
316
317 oops_do(&verify_handle);
318 weak_oops_do(&verify_handle);
319 }
320
321 // This method is implemented here to avoid circular includes between
322 // jniHandles.hpp and thread.hpp.
323 bool JNIHandles::current_thread_in_native() {
324 Thread* thread = Thread::current();
325 return (thread->is_Java_thread() &&
326 JavaThread::current()->thread_state() == _thread_in_native);
327 }
328
329
330 int JNIHandleBlock::_blocks_allocated = 0;
331 JNIHandleBlock* JNIHandleBlock::_block_free_list = NULL;
332 #ifndef PRODUCT
333 JNIHandleBlock* JNIHandleBlock::_block_list = NULL;
334 #endif
335
336 static inline bool is_tagged_free_list(uintptr_t value) {
337 return (value & 1u) != 0;
338 }
339
340 static inline uintptr_t tag_free_list(uintptr_t value) {
341 return value | 1u;
342 }
343
344 static inline uintptr_t untag_free_list(uintptr_t value) {
345 return value & ~(uintptr_t)1u;
346 }
347
348 // There is a freelist of handles running through the JNIHandleBlock
349 // with a tagged next pointer, distinguishing these next pointers from
350 // oops. The freelist handling currently relies on the size of oops
351 // being the same as a native pointer. If this ever changes, then
352 // this freelist handling must change too.
353 STATIC_ASSERT(sizeof(oop) == sizeof(uintptr_t));
354
355 #ifdef ASSERT
356 void JNIHandleBlock::zap() {
357 // Zap block values
358 _top = 0;
359 for (int index = 0; index < block_size_in_oops; index++) {
360 // NOT using Access here; just bare clobbering to NULL, since the
361 // block no longer contains valid oops.
362 _handles[index] = 0;
363 }
364 }
365 #endif // ASSERT
366
367 JNIHandleBlock* JNIHandleBlock::allocate_block(Thread* thread) {
368 assert(thread == NULL || thread == Thread::current(), "sanity check");
369 JNIHandleBlock* block;
370 // Check the thread-local free list for a block so we don't
371 // have to acquire a mutex.
372 if (thread != NULL && thread->free_handle_block() != NULL) {
373 block = thread->free_handle_block();
374 thread->set_free_handle_block(block->_next);
375 }
376 else {
377 // locking with safepoint checking introduces a potential deadlock:
378 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock
379 // - another would hold Threads_lock (jni_AttachCurrentThread) and then
380 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)
381 MutexLocker ml(JNIHandleBlockFreeList_lock,
382 Mutex::_no_safepoint_check_flag);
383 if (_block_free_list == NULL) {
384 // Allocate new block
385 block = new JNIHandleBlock();
386 _blocks_allocated++;
387 block->zap();
388 #ifndef PRODUCT
389 // Link new block to list of all allocated blocks
390 block->_block_list_link = _block_list;
391 _block_list = block;
392 #endif
393 } else {
394 // Get block from free list
395 block = _block_free_list;
396 _block_free_list = _block_free_list->_next;
397 }
398 }
399 block->_top = 0;
400 block->_next = NULL;
401 block->_pop_frame_link = NULL;
402 block->_planned_capacity = block_size_in_oops;
403 // _last, _free_list & _allocate_before_rebuild initialized in allocate_handle
404 debug_only(block->_last = NULL);
405 debug_only(block->_free_list = NULL);
406 debug_only(block->_allocate_before_rebuild = -1);
407 return block;
408 }
409
410
411 void JNIHandleBlock::release_block(JNIHandleBlock* block, Thread* thread) {
412 assert(thread == NULL || thread == Thread::current(), "sanity check");
413 JNIHandleBlock* pop_frame_link = block->pop_frame_link();
414 // Put returned block at the beginning of the thread-local free list.
415 // Note that if thread == NULL, we use it as an implicit argument that
416 // we _don't_ want the block to be kept on the free_handle_block.
417 // See for instance JavaThread::exit().
418 if (thread != NULL ) {
419 block->zap();
420 JNIHandleBlock* freelist = thread->free_handle_block();
421 block->_pop_frame_link = NULL;
422 thread->set_free_handle_block(block);
423
424 // Add original freelist to end of chain
425 if ( freelist != NULL ) {
426 while ( block->_next != NULL ) block = block->_next;
427 block->_next = freelist;
428 }
429 block = NULL;
430 }
431 if (block != NULL) {
432 // Return blocks to free list
433 // locking with safepoint checking introduces a potential deadlock:
434 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock
435 // - another would hold Threads_lock (jni_AttachCurrentThread) and then
436 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)
437 MutexLocker ml(JNIHandleBlockFreeList_lock,
438 Mutex::_no_safepoint_check_flag);
439 while (block != NULL) {
440 block->zap();
441 JNIHandleBlock* next = block->_next;
442 block->_next = _block_free_list;
443 _block_free_list = block;
444 block = next;
445 }
446 }
447 if (pop_frame_link != NULL) {
448 // As a sanity check we release blocks pointed to by the pop_frame_link.
449 // This should never happen (only if PopLocalFrame is not called the
450 // correct number of times).
451 release_block(pop_frame_link, thread);
452 }
453 }
454
455
456 void JNIHandleBlock::oops_do(OopClosure* f) {
457 JNIHandleBlock* current_chain = this;
458 // Iterate over chain of blocks, followed by chains linked through the
459 // pop frame links.
460 while (current_chain != NULL) {
461 for (JNIHandleBlock* current = current_chain; current != NULL;
462 current = current->_next) {
463 assert(current == current_chain || current->pop_frame_link() == NULL,
464 "only blocks first in chain should have pop frame link set");
465 for (int index = 0; index < current->_top; index++) {
466 uintptr_t* addr = &(current->_handles)[index];
467 uintptr_t value = *addr;
468 // traverse heap pointers only, not deleted handles or free list
469 // pointers
470 if (value != 0 && !is_tagged_free_list(value)) {
471 oop* root = (oop*)addr;
472 f->do_oop(root);
473 }
474 }
475 // the next handle block is valid only if current block is full
476 if (current->_top < block_size_in_oops) {
477 break;
478 }
479 }
480 current_chain = current_chain->pop_frame_link();
481 }
482 }
483
484
485 jobject JNIHandleBlock::allocate_handle(oop obj) {
486 assert(Universe::heap()->is_in(obj), "sanity check");
487 if (_top == 0) {
488 // This is the first allocation or the initial block got zapped when
489 // entering a native function. If we have any following blocks they are
490 // not valid anymore.
491 for (JNIHandleBlock* current = _next; current != NULL;
492 current = current->_next) {
493 assert(current->_last == NULL, "only first block should have _last set");
494 assert(current->_free_list == NULL,
495 "only first block should have _free_list set");
496 if (current->_top == 0) {
497 // All blocks after the first clear trailing block are already cleared.
498 #ifdef ASSERT
499 for (current = current->_next; current != NULL; current = current->_next) {
500 assert(current->_top == 0, "trailing blocks must already be cleared");
501 }
502 #endif
503 break;
504 }
505 current->_top = 0;
506 current->zap();
507 }
508 // Clear initial block
509 _free_list = NULL;
510 _allocate_before_rebuild = 0;
511 _last = this;
512 zap();
513 }
514
515 // Try last block
516 if (_last->_top < block_size_in_oops) {
517 oop* handle = (oop*)&(_last->_handles)[_last->_top++];
518 NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, obj);
519 return (jobject) handle;
520 }
521
522 // Try free list
523 if (_free_list != NULL) {
524 oop* handle = (oop*)_free_list;
525 _free_list = (uintptr_t*) untag_free_list(*_free_list);
526 NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, obj);
527 return (jobject) handle;
528 }
529 // Check if unused block follow last
530 if (_last->_next != NULL) {
531 // update last and retry
532 _last = _last->_next;
533 return allocate_handle(obj);
534 }
535
536 // No space available, we have to rebuild free list or expand
537 if (_allocate_before_rebuild == 0) {
538 rebuild_free_list(); // updates _allocate_before_rebuild counter
539 } else {
540 // Append new block
541 Thread* thread = Thread::current();
542 Handle obj_handle(thread, obj);
543 // This can block, so we need to preserve obj across call.
544 _last->_next = JNIHandleBlock::allocate_block(thread);
545 _last = _last->_next;
546 _allocate_before_rebuild--;
547 obj = obj_handle();
548 }
549 return allocate_handle(obj); // retry
550 }
551
552 void JNIHandleBlock::rebuild_free_list() {
553 assert(_allocate_before_rebuild == 0 && _free_list == NULL, "just checking");
554 int free = 0;
555 int blocks = 0;
556 for (JNIHandleBlock* current = this; current != NULL; current = current->_next) {
557 for (int index = 0; index < current->_top; index++) {
558 uintptr_t* handle = &(current->_handles)[index];
559 if (*handle == 0) {
560 // this handle was cleared out by a delete call, reuse it
561 *handle = _free_list == NULL ? 0 : tag_free_list((uintptr_t)_free_list);
562 _free_list = handle;
563 free++;
564 }
565 }
566 // we should not rebuild free list if there are unused handles at the end
567 assert(current->_top == block_size_in_oops, "just checking");
568 blocks++;
569 }
570 // Heuristic: if more than half of the handles are free we rebuild next time
571 // as well, otherwise we append a corresponding number of new blocks before
572 // attempting a free list rebuild again.
573 int total = blocks * block_size_in_oops;
574 int extra = total - 2*free;
575 if (extra > 0) {
576 // Not as many free handles as we would like - compute number of new blocks to append
577 _allocate_before_rebuild = (extra + block_size_in_oops - 1) / block_size_in_oops;
578 }
579 }
580
581
582 bool JNIHandleBlock::contains(jobject handle) const {
583 return ((jobject)&_handles[0] <= handle && handle<(jobject)&_handles[_top]);
584 }
585
586
587 bool JNIHandleBlock::chain_contains(jobject handle) const {
588 for (JNIHandleBlock* current = (JNIHandleBlock*) this; current != NULL; current = current->_next) {
589 if (current->contains(handle)) {
590 return true;
591 }
592 }
593 return false;
594 }
595
596
597 size_t JNIHandleBlock::length() const {
598 size_t result = 1;
599 for (JNIHandleBlock* current = _next; current != NULL; current = current->_next) {
600 result++;
601 }
602 return result;
603 }
604
605 class CountJNIHandleClosure: public OopClosure {
606 private:
607 int _count;
608 public:
609 CountJNIHandleClosure(): _count(0) {}
610 virtual void do_oop(oop* ooph) { _count++; }
611 virtual void do_oop(narrowOop* unused) { ShouldNotReachHere(); }
612 int count() { return _count; }
613 };
614
615 const size_t JNIHandleBlock::get_number_of_live_handles() {
616 CountJNIHandleClosure counter;
617 oops_do(&counter);
618 return counter.count();
619 }
620
621 // This method is not thread-safe, i.e., must be called while holding a lock on the
622 // structure.
623 size_t JNIHandleBlock::memory_usage() const {
624 return length() * sizeof(JNIHandleBlock);
625 }
626
627
628 #ifndef PRODUCT
629
630 bool JNIHandles::is_local_handle(jobject handle) {
631 return JNIHandleBlock::any_contains(handle);
632 }
633
634 bool JNIHandleBlock::any_contains(jobject handle) {
635 assert(handle != NULL, "precondition");
636 for (JNIHandleBlock* current = _block_list; current != NULL; current = current->_block_list_link) {
637 if (current->contains(handle)) {
638 return true;
639 }
640 }
641 return false;
642 }
643
644 void JNIHandleBlock::print_statistics() {
645 int used_blocks = 0;
646 int free_blocks = 0;
647 int used_handles = 0;
648 int free_handles = 0;
649 JNIHandleBlock* block = _block_list;
650 while (block != NULL) {
651 if (block->_top > 0) {
652 used_blocks++;
653 } else {
654 free_blocks++;
655 }
656 used_handles += block->_top;
657 free_handles += (block_size_in_oops - block->_top);
658 block = block->_block_list_link;
659 }
660 tty->print_cr("JNIHandleBlocks statistics");
661 tty->print_cr("- blocks allocated: %d", used_blocks + free_blocks);
662 tty->print_cr("- blocks in use: %d", used_blocks);
663 tty->print_cr("- blocks free: %d", free_blocks);
664 tty->print_cr("- handles in use: %d", used_handles);
665 tty->print_cr("- handles free: %d", free_handles);
666 }
667
668 #endif