1 /*
2 * Copyright (c) 1998, 2020, 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.hpp"
36 #include "runtime/thread.inline.hpp"
37 #include "utilities/align.hpp"
38 #include "utilities/debug.hpp"
39
40 OopStorage* JNIHandles::global_handles() {
41 return _global_handles;
42 }
43
44 OopStorage* JNIHandles::weak_global_handles() {
45 return _weak_global_handles;
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 = OopStorageSet::create_strong("JNI Global");
54 JNIHandles::_weak_global_handles = OopStorageSet::create_weak("JNI Weak");
55 }
56
57 jobject JNIHandles::make_local(oop obj) {
58 return make_local(Thread::current(), obj);
59 }
60
61 // Used by NewLocalRef which requires NULL on out-of-memory
62 jobject JNIHandles::make_local(Thread* thread, oop obj, AllocFailType alloc_failmode) {
63 if (obj == NULL) {
64 return NULL; // ignore null handles
65 } else {
66 assert(oopDesc::is_oop(obj), "not an oop");
67 assert(thread->is_Java_thread(), "not a Java thread");
68 assert(!current_thread_in_native(), "must not be in native");
69 return thread->active_handles()->allocate_handle(obj, alloc_failmode);
70 }
71 }
72
73 static void report_handle_allocation_failure(AllocFailType alloc_failmode,
74 const char* handle_kind) {
75 if (alloc_failmode == AllocFailStrategy::EXIT_OOM) {
76 // Fake size value, since we don't know the min allocation size here.
77 vm_exit_out_of_memory(sizeof(oop), OOM_MALLOC_ERROR,
78 "Cannot create %s JNI handle", handle_kind);
79 } else {
80 assert(alloc_failmode == AllocFailStrategy::RETURN_NULL, "invariant");
81 }
82 }
83
84 jobject JNIHandles::make_global(Handle obj, AllocFailType alloc_failmode) {
85 assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");
86 assert(!current_thread_in_native(), "must not be in native");
87 jobject res = NULL;
88 if (!obj.is_null()) {
89 // ignore null handles
90 assert(oopDesc::is_oop(obj()), "not an oop");
91 oop* ptr = global_handles()->allocate();
92 // Return NULL on allocation failure.
93 if (ptr != NULL) {
94 assert(*ptr == NULL, "invariant");
95 NativeAccess<>::oop_store(ptr, obj());
96 res = reinterpret_cast<jobject>(ptr);
97 } else {
98 report_handle_allocation_failure(alloc_failmode, "global");
99 }
100 }
101
102 return res;
103 }
104
105 jobject JNIHandles::make_weak_global(Handle obj, AllocFailType alloc_failmode) {
106 assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");
107 assert(!current_thread_in_native(), "must not be in native");
108 jobject res = NULL;
109 if (!obj.is_null()) {
110 // ignore null handles
111 assert(oopDesc::is_oop(obj()), "not an oop");
112 oop* ptr = weak_global_handles()->allocate();
113 // Return NULL on allocation failure.
114 if (ptr != NULL) {
115 assert(*ptr == NULL, "invariant");
116 NativeAccess<ON_PHANTOM_OOP_REF>::oop_store(ptr, obj());
117 char* tptr = reinterpret_cast<char*>(ptr) + weak_tag_value;
118 res = reinterpret_cast<jobject>(tptr);
119 } else {
120 report_handle_allocation_failure(alloc_failmode, "weak global");
121 }
122 }
123 return res;
124 }
125
126 // Resolve some erroneous cases to NULL, rather than treating them as
127 // possibly unchecked errors. In particular, deleted handles are
128 // treated as NULL (though a deleted and later reallocated handle
129 // isn't detected).
130 oop JNIHandles::resolve_external_guard(jobject handle) {
131 oop result = NULL;
132 if (handle != NULL) {
133 result = resolve_impl<DECORATORS_NONE, true /* external_guard */>(handle);
134 }
135 return result;
136 }
137
138 bool JNIHandles::is_global_weak_cleared(jweak handle) {
139 assert(handle != NULL, "precondition");
140 assert(is_jweak(handle), "not a weak handle");
141 oop* oop_ptr = jweak_ptr(handle);
142 oop value = NativeAccess<ON_PHANTOM_OOP_REF | AS_NO_KEEPALIVE>::oop_load(oop_ptr);
143 return value == NULL;
144 }
145
146 void JNIHandles::destroy_global(jobject handle) {
147 if (handle != NULL) {
148 assert(!is_jweak(handle), "wrong method for detroying jweak");
149 oop* oop_ptr = jobject_ptr(handle);
150 NativeAccess<>::oop_store(oop_ptr, (oop)NULL);
151 global_handles()->release(oop_ptr);
152 }
153 }
154
155
156 void JNIHandles::destroy_weak_global(jobject handle) {
157 if (handle != NULL) {
158 assert(is_jweak(handle), "JNI handle not jweak");
159 oop* oop_ptr = jweak_ptr(handle);
160 NativeAccess<ON_PHANTOM_OOP_REF>::oop_store(oop_ptr, (oop)NULL);
161 weak_global_handles()->release(oop_ptr);
162 }
163 }
164
165
166 void JNIHandles::oops_do(OopClosure* f) {
167 global_handles()->oops_do(f);
168 }
169
170
171 void JNIHandles::weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f) {
172 weak_global_handles()->weak_oops_do(is_alive, f);
173 }
174
175
176 void JNIHandles::weak_oops_do(OopClosure* f) {
177 weak_global_handles()->weak_oops_do(f);
178 }
179
180 bool JNIHandles::is_global_storage(const OopStorage* storage) {
181 return _global_handles == storage;
182 }
183
184 inline bool is_storage_handle(const OopStorage* storage, const oop* ptr) {
185 return storage->allocation_status(ptr) == OopStorage::ALLOCATED_ENTRY;
186 }
187
188
189 jobjectRefType JNIHandles::handle_type(Thread* thread, jobject handle) {
190 assert(handle != NULL, "precondition");
191 jobjectRefType result = JNIInvalidRefType;
192 if (is_jweak(handle)) {
193 if (is_storage_handle(weak_global_handles(), jweak_ptr(handle))) {
194 result = JNIWeakGlobalRefType;
195 }
196 } else {
197 switch (global_handles()->allocation_status(jobject_ptr(handle))) {
198 case OopStorage::ALLOCATED_ENTRY:
199 result = JNIGlobalRefType;
200 break;
201
202 case OopStorage::UNALLOCATED_ENTRY:
203 break; // Invalid global handle
204
205 case OopStorage::INVALID_ENTRY:
206 // Not in global storage. Might be a local handle.
207 if (is_local_handle(thread, handle) ||
208 (thread->is_Java_thread() &&
209 is_frame_handle((JavaThread*)thread, handle))) {
210 result = JNILocalRefType;
211 }
212 break;
213
214 default:
215 ShouldNotReachHere();
216 }
217 }
218 return result;
219 }
220
221
222 bool JNIHandles::is_local_handle(Thread* thread, jobject handle) {
223 assert(handle != NULL, "precondition");
224 JNIHandleBlock* block = thread->active_handles();
225
226 // Look back past possible native calls to jni_PushLocalFrame.
227 while (block != NULL) {
228 if (block->chain_contains(handle)) {
229 return true;
230 }
231 block = block->pop_frame_link();
232 }
233 return false;
234 }
235
236
237 // Determine if the handle is somewhere in the current thread's stack.
238 // We easily can't isolate any particular stack frame the handle might
239 // come from, so we'll check the whole stack.
240
241 bool JNIHandles::is_frame_handle(JavaThread* thr, jobject handle) {
242 assert(handle != NULL, "precondition");
243 // If there is no java frame, then this must be top level code, such
244 // as the java command executable, in which case, this type of handle
245 // is not permitted.
246 return (thr->has_last_Java_frame() &&
247 thr->is_in_stack_range_incl((address)handle, (address)thr->last_Java_sp()));
248 }
249
250
251 bool JNIHandles::is_global_handle(jobject handle) {
252 assert(handle != NULL, "precondition");
253 return !is_jweak(handle) && is_storage_handle(global_handles(), jobject_ptr(handle));
254 }
255
256
257 bool JNIHandles::is_weak_global_handle(jobject handle) {
258 assert(handle != NULL, "precondition");
259 return is_jweak(handle) && is_storage_handle(weak_global_handles(), jweak_ptr(handle));
260 }
261
262 size_t JNIHandles::global_handle_memory_usage() {
263 return global_handles()->total_memory_usage();
264 }
265
266 size_t JNIHandles::weak_global_handle_memory_usage() {
267 return weak_global_handles()->total_memory_usage();
268 }
269
270
271 // We assume this is called at a safepoint: no lock is needed.
272 void JNIHandles::print_on(outputStream* st) {
273 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
274
275 st->print_cr("JNI global refs: " SIZE_FORMAT ", weak refs: " SIZE_FORMAT,
276 global_handles()->allocation_count(),
277 weak_global_handles()->allocation_count());
278 st->cr();
279 st->flush();
280 }
281
282 void JNIHandles::print() { print_on(tty); }
283
284 class VerifyJNIHandles: public OopClosure {
285 public:
286 virtual void do_oop(oop* root) {
287 guarantee(oopDesc::is_oop_or_null(RawAccess<>::oop_load(root)), "Invalid oop");
288 }
289 virtual void do_oop(narrowOop* root) { ShouldNotReachHere(); }
290 };
291
292 void JNIHandles::verify() {
293 VerifyJNIHandles verify_handle;
294
295 oops_do(&verify_handle);
296 weak_oops_do(&verify_handle);
297 }
298
299 // This method is implemented here to avoid circular includes between
300 // jniHandles.hpp and thread.hpp.
301 bool JNIHandles::current_thread_in_native() {
302 Thread* thread = Thread::current();
303 return (thread->is_Java_thread() &&
304 JavaThread::current()->thread_state() == _thread_in_native);
305 }
306
307
308 int JNIHandleBlock::_blocks_allocated = 0;
309 JNIHandleBlock* JNIHandleBlock::_block_free_list = NULL;
310 #ifndef PRODUCT
311 JNIHandleBlock* JNIHandleBlock::_block_list = NULL;
312 #endif
313
314 static inline bool is_tagged_free_list(uintptr_t value) {
315 return (value & 1u) != 0;
316 }
317
318 static inline uintptr_t tag_free_list(uintptr_t value) {
319 return value | 1u;
320 }
321
322 static inline uintptr_t untag_free_list(uintptr_t value) {
323 return value & ~(uintptr_t)1u;
324 }
325
326 // There is a freelist of handles running through the JNIHandleBlock
327 // with a tagged next pointer, distinguishing these next pointers from
328 // oops. The freelist handling currently relies on the size of oops
329 // being the same as a native pointer. If this ever changes, then
330 // this freelist handling must change too.
331 STATIC_ASSERT(sizeof(oop) == sizeof(uintptr_t));
332
333 #ifdef ASSERT
334 void JNIHandleBlock::zap() {
335 // Zap block values
336 _top = 0;
337 for (int index = 0; index < block_size_in_oops; index++) {
338 // NOT using Access here; just bare clobbering to NULL, since the
339 // block no longer contains valid oops.
340 _handles[index] = 0;
341 }
342 }
343 #endif // ASSERT
344
345 JNIHandleBlock* JNIHandleBlock::allocate_block(Thread* thread, AllocFailType alloc_failmode) {
346 assert(thread == NULL || thread == Thread::current(), "sanity check");
347 JNIHandleBlock* block;
348 // Check the thread-local free list for a block so we don't
349 // have to acquire a mutex.
350 if (thread != NULL && thread->free_handle_block() != NULL) {
351 block = thread->free_handle_block();
352 thread->set_free_handle_block(block->_next);
353 }
354 else {
355 // locking with safepoint checking introduces a potential deadlock:
356 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock
357 // - another would hold Threads_lock (jni_AttachCurrentThread) and then
358 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)
359 MutexLocker ml(JNIHandleBlockFreeList_lock,
360 Mutex::_no_safepoint_check_flag);
361 if (_block_free_list == NULL) {
362 // Allocate new block
363 if (alloc_failmode == AllocFailStrategy::RETURN_NULL) {
364 block = new (std::nothrow) JNIHandleBlock();
365 if (block == NULL) {
366 return NULL;
367 }
368 } else {
369 block = new JNIHandleBlock();
370 }
371 _blocks_allocated++;
372 block->zap();
373 #ifndef PRODUCT
374 // Link new block to list of all allocated blocks
375 block->_block_list_link = _block_list;
376 _block_list = block;
377 #endif
378 } else {
379 // Get block from free list
380 block = _block_free_list;
381 _block_free_list = _block_free_list->_next;
382 }
383 }
384 block->_top = 0;
385 block->_next = NULL;
386 block->_pop_frame_link = NULL;
387 block->_planned_capacity = block_size_in_oops;
388 // _last, _free_list & _allocate_before_rebuild initialized in allocate_handle
389 debug_only(block->_last = NULL);
390 debug_only(block->_free_list = NULL);
391 debug_only(block->_allocate_before_rebuild = -1);
392 return block;
393 }
394
395
396 void JNIHandleBlock::release_block(JNIHandleBlock* block, Thread* thread) {
397 assert(thread == NULL || thread == Thread::current(), "sanity check");
398 JNIHandleBlock* pop_frame_link = block->pop_frame_link();
399 // Put returned block at the beginning of the thread-local free list.
400 // Note that if thread == NULL, we use it as an implicit argument that
401 // we _don't_ want the block to be kept on the free_handle_block.
402 // See for instance JavaThread::exit().
403 if (thread != NULL ) {
404 block->zap();
405 JNIHandleBlock* freelist = thread->free_handle_block();
406 block->_pop_frame_link = NULL;
407 thread->set_free_handle_block(block);
408
409 // Add original freelist to end of chain
410 if ( freelist != NULL ) {
411 while ( block->_next != NULL ) block = block->_next;
412 block->_next = freelist;
413 }
414 block = NULL;
415 }
416 if (block != NULL) {
417 // Return blocks to free list
418 // locking with safepoint checking introduces a potential deadlock:
419 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock
420 // - another would hold Threads_lock (jni_AttachCurrentThread) and then
421 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)
422 MutexLocker ml(JNIHandleBlockFreeList_lock,
423 Mutex::_no_safepoint_check_flag);
424 while (block != NULL) {
425 block->zap();
426 JNIHandleBlock* next = block->_next;
427 block->_next = _block_free_list;
428 _block_free_list = block;
429 block = next;
430 }
431 }
432 if (pop_frame_link != NULL) {
433 // As a sanity check we release blocks pointed to by the pop_frame_link.
434 // This should never happen (only if PopLocalFrame is not called the
435 // correct number of times).
436 release_block(pop_frame_link, thread);
437 }
438 }
439
440
441 void JNIHandleBlock::oops_do(OopClosure* f) {
442 JNIHandleBlock* current_chain = this;
443 // Iterate over chain of blocks, followed by chains linked through the
444 // pop frame links.
445 while (current_chain != NULL) {
446 for (JNIHandleBlock* current = current_chain; current != NULL;
447 current = current->_next) {
448 assert(current == current_chain || current->pop_frame_link() == NULL,
449 "only blocks first in chain should have pop frame link set");
450 for (int index = 0; index < current->_top; index++) {
451 uintptr_t* addr = &(current->_handles)[index];
452 uintptr_t value = *addr;
453 // traverse heap pointers only, not deleted handles or free list
454 // pointers
455 if (value != 0 && !is_tagged_free_list(value)) {
456 oop* root = (oop*)addr;
457 f->do_oop(root);
458 }
459 }
460 // the next handle block is valid only if current block is full
461 if (current->_top < block_size_in_oops) {
462 break;
463 }
464 }
465 current_chain = current_chain->pop_frame_link();
466 }
467 }
468
469
470 jobject JNIHandleBlock::allocate_handle(oop obj, AllocFailType alloc_failmode) {
471 assert(Universe::heap()->is_in(obj), "sanity check");
472 if (_top == 0) {
473 // This is the first allocation or the initial block got zapped when
474 // entering a native function. If we have any following blocks they are
475 // not valid anymore.
476 for (JNIHandleBlock* current = _next; current != NULL;
477 current = current->_next) {
478 assert(current->_last == NULL, "only first block should have _last set");
479 assert(current->_free_list == NULL,
480 "only first block should have _free_list set");
481 if (current->_top == 0) {
482 // All blocks after the first clear trailing block are already cleared.
483 #ifdef ASSERT
484 for (current = current->_next; current != NULL; current = current->_next) {
485 assert(current->_top == 0, "trailing blocks must already be cleared");
486 }
487 #endif
488 break;
489 }
490 current->_top = 0;
491 current->zap();
492 }
493 // Clear initial block
494 _free_list = NULL;
495 _allocate_before_rebuild = 0;
496 _last = this;
497 zap();
498 }
499
500 // Try last block
501 if (_last->_top < block_size_in_oops) {
502 oop* handle = (oop*)&(_last->_handles)[_last->_top++];
503 NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, obj);
504 return (jobject) handle;
505 }
506
507 // Try free list
508 if (_free_list != NULL) {
509 oop* handle = (oop*)_free_list;
510 _free_list = (uintptr_t*) untag_free_list(*_free_list);
511 NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, obj);
512 return (jobject) handle;
513 }
514 // Check if unused block follow last
515 if (_last->_next != NULL) {
516 // update last and retry
517 _last = _last->_next;
518 return allocate_handle(obj, alloc_failmode);
519 }
520
521 // No space available, we have to rebuild free list or expand
522 if (_allocate_before_rebuild == 0) {
523 rebuild_free_list(); // updates _allocate_before_rebuild counter
524 } else {
525 // Append new block
526 Thread* thread = Thread::current();
527 Handle obj_handle(thread, obj);
528 // This can block, so we need to preserve obj across call.
529 _last->_next = JNIHandleBlock::allocate_block(thread, alloc_failmode);
530 if (_last->_next == NULL) {
531 return NULL;
532 }
533 _last = _last->_next;
534 _allocate_before_rebuild--;
535 obj = obj_handle();
536 }
537 return allocate_handle(obj, alloc_failmode); // retry
538 }
539
540 void JNIHandleBlock::rebuild_free_list() {
541 assert(_allocate_before_rebuild == 0 && _free_list == NULL, "just checking");
542 int free = 0;
543 int blocks = 0;
544 for (JNIHandleBlock* current = this; current != NULL; current = current->_next) {
545 for (int index = 0; index < current->_top; index++) {
546 uintptr_t* handle = &(current->_handles)[index];
547 if (*handle == 0) {
548 // this handle was cleared out by a delete call, reuse it
549 *handle = _free_list == NULL ? 0 : tag_free_list((uintptr_t)_free_list);
550 _free_list = handle;
551 free++;
552 }
553 }
554 // we should not rebuild free list if there are unused handles at the end
555 assert(current->_top == block_size_in_oops, "just checking");
556 blocks++;
557 }
558 // Heuristic: if more than half of the handles are free we rebuild next time
559 // as well, otherwise we append a corresponding number of new blocks before
560 // attempting a free list rebuild again.
561 int total = blocks * block_size_in_oops;
562 int extra = total - 2*free;
563 if (extra > 0) {
564 // Not as many free handles as we would like - compute number of new blocks to append
565 _allocate_before_rebuild = (extra + block_size_in_oops - 1) / block_size_in_oops;
566 }
567 }
568
569
570 bool JNIHandleBlock::contains(jobject handle) const {
571 return ((jobject)&_handles[0] <= handle && handle<(jobject)&_handles[_top]);
572 }
573
574
575 bool JNIHandleBlock::chain_contains(jobject handle) const {
576 for (JNIHandleBlock* current = (JNIHandleBlock*) this; current != NULL; current = current->_next) {
577 if (current->contains(handle)) {
578 return true;
579 }
580 }
581 return false;
582 }
583
584
585 size_t JNIHandleBlock::length() const {
586 size_t result = 1;
587 for (JNIHandleBlock* current = _next; current != NULL; current = current->_next) {
588 result++;
589 }
590 return result;
591 }
592
593 class CountJNIHandleClosure: public OopClosure {
594 private:
595 int _count;
596 public:
597 CountJNIHandleClosure(): _count(0) {}
598 virtual void do_oop(oop* ooph) { _count++; }
599 virtual void do_oop(narrowOop* unused) { ShouldNotReachHere(); }
600 int count() { return _count; }
601 };
602
603 const size_t JNIHandleBlock::get_number_of_live_handles() {
604 CountJNIHandleClosure counter;
605 oops_do(&counter);
606 return counter.count();
607 }
608
609 // This method is not thread-safe, i.e., must be called while holding a lock on the
610 // structure.
611 size_t JNIHandleBlock::memory_usage() const {
612 return length() * sizeof(JNIHandleBlock);
613 }
614
615
616 #ifndef PRODUCT
617
618 bool JNIHandles::is_local_handle(jobject handle) {
619 return JNIHandleBlock::any_contains(handle);
620 }
621
622 bool JNIHandleBlock::any_contains(jobject handle) {
623 assert(handle != NULL, "precondition");
624 for (JNIHandleBlock* current = _block_list; current != NULL; current = current->_block_list_link) {
625 if (current->contains(handle)) {
626 return true;
627 }
628 }
629 return false;
630 }
631
632 void JNIHandleBlock::print_statistics() {
633 int used_blocks = 0;
634 int free_blocks = 0;
635 int used_handles = 0;
636 int free_handles = 0;
637 JNIHandleBlock* block = _block_list;
638 while (block != NULL) {
639 if (block->_top > 0) {
640 used_blocks++;
641 } else {
642 free_blocks++;
643 }
644 used_handles += block->_top;
645 free_handles += (block_size_in_oops - block->_top);
646 block = block->_block_list_link;
647 }
648 tty->print_cr("JNIHandleBlocks statistics");
649 tty->print_cr("- blocks allocated: %d", used_blocks + free_blocks);
650 tty->print_cr("- blocks in use: %d", used_blocks);
651 tty->print_cr("- blocks free: %d", free_blocks);
652 tty->print_cr("- handles in use: %d", used_handles);
653 tty->print_cr("- handles free: %d", free_handles);
654 }
655
656 #endif