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<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 NativeAccess<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 = NativeAccess<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 NativeAccess<>::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 NativeAccess<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 oopDesc::verify(*root);
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
331 // JNI weaks are handled concurrently in ZGC, so they can't be verified here
332 if (!UseZGC) {
333 weak_oops_do(&verify_handle);
334 }
335 }
336
337 // This method is implemented here to avoid circular includes between
338 // jniHandles.hpp and thread.hpp.
339 bool JNIHandles::current_thread_in_native() {
340 Thread* thread = Thread::current();
341 return (thread->is_Java_thread() &&
342 JavaThread::current()->thread_state() == _thread_in_native);
343 }
344
345
346 void jni_handles_init() {
347 JNIHandles::initialize();
348 }
349
350
351 int JNIHandleBlock::_blocks_allocated = 0;
352 JNIHandleBlock* JNIHandleBlock::_block_free_list = NULL;
353 #ifndef PRODUCT
354 JNIHandleBlock* JNIHandleBlock::_block_list = NULL;
355 #endif
356
357
358 #ifdef ASSERT
359 void JNIHandleBlock::zap() {
360 // Zap block values
361 _top = 0;
362 for (int index = 0; index < block_size_in_oops; index++) {
363 // NOT using Access here; just bare clobbering to NULL, since the
364 // block no longer contains valid oops.
365 _handles[index] = NULL;
366 }
367 }
368 #endif // ASSERT
369
370 JNIHandleBlock* JNIHandleBlock::allocate_block(Thread* thread) {
371 assert(thread == NULL || thread == Thread::current(), "sanity check");
372 JNIHandleBlock* block;
373 // Check the thread-local free list for a block so we don't
374 // have to acquire a mutex.
375 if (thread != NULL && thread->free_handle_block() != NULL) {
376 block = thread->free_handle_block();
377 thread->set_free_handle_block(block->_next);
378 }
379 else {
380 // locking with safepoint checking introduces a potential deadlock:
381 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock
382 // - another would hold Threads_lock (jni_AttachCurrentThread) and then
383 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)
384 MutexLockerEx ml(JNIHandleBlockFreeList_lock,
385 Mutex::_no_safepoint_check_flag);
386 if (_block_free_list == NULL) {
387 // Allocate new block
388 block = new JNIHandleBlock();
389 _blocks_allocated++;
390 block->zap();
391 #ifndef PRODUCT
392 // Link new block to list of all allocated blocks
393 block->_block_list_link = _block_list;
394 _block_list = block;
395 #endif
396 } else {
397 // Get block from free list
398 block = _block_free_list;
399 _block_free_list = _block_free_list->_next;
400 }
401 }
402 block->_top = 0;
403 block->_next = NULL;
404 block->_pop_frame_link = NULL;
405 block->_planned_capacity = block_size_in_oops;
406 // _last, _free_list & _allocate_before_rebuild initialized in allocate_handle
407 debug_only(block->_last = NULL);
408 debug_only(block->_free_list = NULL);
409 debug_only(block->_allocate_before_rebuild = -1);
410 return block;
411 }
412
413
414 void JNIHandleBlock::release_block(JNIHandleBlock* block, Thread* thread) {
415 assert(thread == NULL || thread == Thread::current(), "sanity check");
416 JNIHandleBlock* pop_frame_link = block->pop_frame_link();
417 // Put returned block at the beginning of the thread-local free list.
418 // Note that if thread == NULL, we use it as an implicit argument that
419 // we _don't_ want the block to be kept on the free_handle_block.
420 // See for instance JavaThread::exit().
421 if (thread != NULL ) {
422 block->zap();
423 JNIHandleBlock* freelist = thread->free_handle_block();
424 block->_pop_frame_link = NULL;
425 thread->set_free_handle_block(block);
426
427 // Add original freelist to end of chain
428 if ( freelist != NULL ) {
429 while ( block->_next != NULL ) block = block->_next;
430 block->_next = freelist;
431 }
432 block = NULL;
433 }
434 if (block != NULL) {
435 // Return blocks to free list
436 // locking with safepoint checking introduces a potential deadlock:
437 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock
438 // - another would hold Threads_lock (jni_AttachCurrentThread) and then
439 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)
440 MutexLockerEx ml(JNIHandleBlockFreeList_lock,
441 Mutex::_no_safepoint_check_flag);
442 while (block != NULL) {
443 block->zap();
444 JNIHandleBlock* next = block->_next;
445 block->_next = _block_free_list;
446 _block_free_list = block;
447 block = next;
448 }
449 }
450 if (pop_frame_link != NULL) {
451 // As a sanity check we release blocks pointed to by the pop_frame_link.
452 // This should never happen (only if PopLocalFrame is not called the
453 // correct number of times).
454 release_block(pop_frame_link, thread);
455 }
456 }
457
458
459 void JNIHandleBlock::oops_do(OopClosure* f) {
460 JNIHandleBlock* current_chain = this;
461 // Iterate over chain of blocks, followed by chains linked through the
462 // pop frame links.
463 while (current_chain != NULL) {
464 for (JNIHandleBlock* current = current_chain; current != NULL;
465 current = current->_next) {
466 assert(current == current_chain || current->pop_frame_link() == NULL,
467 "only blocks first in chain should have pop frame link set");
468 for (int index = 0; index < current->_top; index++) {
469 oop* root = &(current->_handles)[index];
470 oop value = *root;
471 // traverse heap pointers only, not deleted handles or free list
472 // pointers
473 if (value != NULL && Universe::heap()->is_in_reserved(value)) {
474 f->do_oop(root);
475 }
476 }
477 // the next handle block is valid only if current block is full
478 if (current->_top < block_size_in_oops) {
479 break;
480 }
481 }
482 current_chain = current_chain->pop_frame_link();
483 }
484 }
485
486
487 jobject JNIHandleBlock::allocate_handle(oop obj) {
488 assert(Universe::heap()->is_in_reserved(obj), "sanity check");
489 if (_top == 0) {
490 // This is the first allocation or the initial block got zapped when
491 // entering a native function. If we have any following blocks they are
492 // not valid anymore.
493 for (JNIHandleBlock* current = _next; current != NULL;
494 current = current->_next) {
495 assert(current->_last == NULL, "only first block should have _last set");
496 assert(current->_free_list == NULL,
497 "only first block should have _free_list set");
498 if (current->_top == 0) {
499 // All blocks after the first clear trailing block are already cleared.
500 #ifdef ASSERT
501 for (current = current->_next; current != NULL; current = current->_next) {
502 assert(current->_top == 0, "trailing blocks must already be cleared");
503 }
504 #endif
505 break;
506 }
507 current->_top = 0;
508 current->zap();
509 }
510 // Clear initial block
511 _free_list = NULL;
512 _allocate_before_rebuild = 0;
513 _last = this;
514 zap();
515 }
516
517 // Try last block
518 if (_last->_top < block_size_in_oops) {
519 oop* handle = &(_last->_handles)[_last->_top++];
520 NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, obj);
521 return (jobject) handle;
522 }
523
524 // Try free list
525 if (_free_list != NULL) {
526 oop* handle = _free_list;
527 _free_list = (oop*) *_free_list;
528 NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, obj);
529 return (jobject) handle;
530 }
531 // Check if unused block follow last
532 if (_last->_next != NULL) {
533 // update last and retry
534 _last = _last->_next;
535 return allocate_handle(obj);
536 }
537
538 // No space available, we have to rebuild free list or expand
539 if (_allocate_before_rebuild == 0) {
540 rebuild_free_list(); // updates _allocate_before_rebuild counter
541 } else {
542 // Append new block
543 Thread* thread = Thread::current();
544 Handle obj_handle(thread, obj);
545 // This can block, so we need to preserve obj across call.
546 _last->_next = JNIHandleBlock::allocate_block(thread);
547 _last = _last->_next;
548 _allocate_before_rebuild--;
549 obj = obj_handle();
550 }
551 return allocate_handle(obj); // retry
552 }
553
554 void JNIHandleBlock::rebuild_free_list() {
555 assert(_allocate_before_rebuild == 0 && _free_list == NULL, "just checking");
556 int free = 0;
557 int blocks = 0;
558 for (JNIHandleBlock* current = this; current != NULL; current = current->_next) {
559 for (int index = 0; index < current->_top; index++) {
560 oop* handle = &(current->_handles)[index];
561 if (*handle == NULL) {
562 // this handle was cleared out by a delete call, reuse it
563 *handle = (oop) _free_list;
564 _free_list = handle;
565 free++;
566 }
567 }
568 // we should not rebuild free list if there are unused handles at the end
569 assert(current->_top == block_size_in_oops, "just checking");
570 blocks++;
571 }
572 // Heuristic: if more than half of the handles are free we rebuild next time
573 // as well, otherwise we append a corresponding number of new blocks before
574 // attempting a free list rebuild again.
575 int total = blocks * block_size_in_oops;
576 int extra = total - 2*free;
577 if (extra > 0) {
578 // Not as many free handles as we would like - compute number of new blocks to append
579 _allocate_before_rebuild = (extra + block_size_in_oops - 1) / block_size_in_oops;
580 }
581 }
582
583
584 bool JNIHandleBlock::contains(jobject handle) const {
585 return ((jobject)&_handles[0] <= handle && handle<(jobject)&_handles[_top]);
586 }
587
588
589 bool JNIHandleBlock::chain_contains(jobject handle) const {
590 for (JNIHandleBlock* current = (JNIHandleBlock*) this; current != NULL; current = current->_next) {
591 if (current->contains(handle)) {
592 return true;
593 }
594 }
595 return false;
596 }
597
598
599 size_t JNIHandleBlock::length() const {
600 size_t result = 1;
601 for (JNIHandleBlock* current = _next; current != NULL; current = current->_next) {
602 result++;
603 }
604 return result;
605 }
606
607 class CountJNIHandleClosure: public OopClosure {
608 private:
609 int _count;
610 public:
611 CountJNIHandleClosure(): _count(0) {}
612 virtual void do_oop(oop* ooph) { _count++; }
613 virtual void do_oop(narrowOop* unused) { ShouldNotReachHere(); }
614 int count() { return _count; }
615 };
616
617 const size_t JNIHandleBlock::get_number_of_live_handles() {
618 CountJNIHandleClosure counter;
619 oops_do(&counter);
620 return counter.count();
621 }
622
623 // This method is not thread-safe, i.e., must be called while holding a lock on the
624 // structure.
625 size_t JNIHandleBlock::memory_usage() const {
626 return length() * sizeof(JNIHandleBlock);
627 }
628
629
630 #ifndef PRODUCT
631
632 bool JNIHandles::is_local_handle(jobject handle) {
633 return JNIHandleBlock::any_contains(handle);
634 }
635
636 bool JNIHandleBlock::any_contains(jobject handle) {
637 assert(handle != NULL, "precondition");
638 for (JNIHandleBlock* current = _block_list; current != NULL; current = current->_block_list_link) {
639 if (current->contains(handle)) {
640 return true;
641 }
642 }
643 return false;
644 }
645
646 void JNIHandleBlock::print_statistics() {
647 int used_blocks = 0;
648 int free_blocks = 0;
649 int used_handles = 0;
650 int free_handles = 0;
651 JNIHandleBlock* block = _block_list;
652 while (block != NULL) {
653 if (block->_top > 0) {
654 used_blocks++;
655 } else {
656 free_blocks++;
657 }
658 used_handles += block->_top;
659 free_handles += (block_size_in_oops - block->_top);
660 block = block->_block_list_link;
661 }
662 tty->print_cr("JNIHandleBlocks statistics");
663 tty->print_cr("- blocks allocated: %d", used_blocks + free_blocks);
664 tty->print_cr("- blocks in use: %d", used_blocks);
665 tty->print_cr("- blocks free: %d", free_blocks);
666 tty->print_cr("- handles in use: %d", used_handles);
667 tty->print_cr("- handles free: %d", free_handles);
668 }
669
670 #endif