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