Mon, 20 Jun 2016 22:46:28 -0700
8155968: Update command line options
Reviewed-by: gthornbr, hseigel, mschoene
Contributed-by: gerard.ziemski@oracle.com
1 /*
2 * Copyright (c) 1998, 2015, 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 */
25 #include "precompiled.hpp"
26 #include "classfile/systemDictionary.hpp"
27 #include "oops/oop.inline.hpp"
28 #include "prims/jvmtiExport.hpp"
29 #include "runtime/jniHandles.hpp"
30 #include "runtime/mutexLocker.hpp"
31 #include "runtime/thread.inline.hpp"
33 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
35 JNIHandleBlock* JNIHandles::_global_handles = NULL;
36 JNIHandleBlock* JNIHandles::_weak_global_handles = NULL;
37 oop JNIHandles::_deleted_handle = NULL;
40 jobject JNIHandles::make_local(oop obj) {
41 if (obj == NULL) {
42 return NULL; // ignore null handles
43 } else {
44 Thread* thread = Thread::current();
45 assert(Universe::heap()->is_in_reserved(obj), "sanity check");
46 return thread->active_handles()->allocate_handle(obj);
47 }
48 }
51 // optimized versions
53 jobject JNIHandles::make_local(Thread* thread, oop obj) {
54 if (obj == NULL) {
55 return NULL; // ignore null handles
56 } else {
57 assert(Universe::heap()->is_in_reserved(obj), "sanity check");
58 return thread->active_handles()->allocate_handle(obj);
59 }
60 }
63 jobject JNIHandles::make_local(JNIEnv* env, oop obj) {
64 if (obj == NULL) {
65 return NULL; // ignore null handles
66 } else {
67 JavaThread* thread = JavaThread::thread_from_jni_environment(env);
68 assert(Universe::heap()->is_in_reserved(obj), "sanity check");
69 return thread->active_handles()->allocate_handle(obj);
70 }
71 }
74 jobject JNIHandles::make_global(Handle obj) {
75 assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");
76 jobject res = NULL;
77 if (!obj.is_null()) {
78 // ignore null handles
79 MutexLocker ml(JNIGlobalHandle_lock);
80 assert(Universe::heap()->is_in_reserved(obj()), "sanity check");
81 res = _global_handles->allocate_handle(obj());
82 } else {
83 CHECK_UNHANDLED_OOPS_ONLY(Thread::current()->clear_unhandled_oops());
84 }
86 return res;
87 }
90 jobject JNIHandles::make_weak_global(Handle obj) {
91 assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC");
92 jobject res = NULL;
93 if (!obj.is_null()) {
94 // ignore null handles
95 MutexLocker ml(JNIGlobalHandle_lock);
96 assert(Universe::heap()->is_in_reserved(obj()), "sanity check");
97 res = _weak_global_handles->allocate_handle(obj());
98 } else {
99 CHECK_UNHANDLED_OOPS_ONLY(Thread::current()->clear_unhandled_oops());
100 }
101 return res;
102 }
105 void JNIHandles::destroy_global(jobject handle) {
106 if (handle != NULL) {
107 assert(is_global_handle(handle), "Invalid delete of global JNI handle");
108 *((oop*)handle) = deleted_handle(); // Mark the handle as deleted, allocate will reuse it
109 }
110 }
113 void JNIHandles::destroy_weak_global(jobject handle) {
114 if (handle != NULL) {
115 assert(!CheckJNICalls || is_weak_global_handle(handle), "Invalid delete of weak global JNI handle");
116 *((oop*)handle) = deleted_handle(); // Mark the handle as deleted, allocate will reuse it
117 }
118 }
121 void JNIHandles::oops_do(OopClosure* f) {
122 f->do_oop(&_deleted_handle);
123 _global_handles->oops_do(f);
124 }
127 void JNIHandles::weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f) {
128 _weak_global_handles->weak_oops_do(is_alive, f);
129 }
132 void JNIHandles::initialize() {
133 _global_handles = JNIHandleBlock::allocate_block();
134 _weak_global_handles = JNIHandleBlock::allocate_block();
135 EXCEPTION_MARK;
136 // We will never reach the CATCH below since Exceptions::_throw will cause
137 // the VM to exit if an exception is thrown during initialization
138 Klass* k = SystemDictionary::Object_klass();
139 _deleted_handle = InstanceKlass::cast(k)->allocate_instance(CATCH);
140 }
143 bool JNIHandles::is_local_handle(Thread* thread, jobject handle) {
144 JNIHandleBlock* block = thread->active_handles();
146 // Look back past possible native calls to jni_PushLocalFrame.
147 while (block != NULL) {
148 if (block->chain_contains(handle)) {
149 return true;
150 }
151 block = block->pop_frame_link();
152 }
153 return false;
154 }
157 // Determine if the handle is somewhere in the current thread's stack.
158 // We easily can't isolate any particular stack frame the handle might
159 // come from, so we'll check the whole stack.
161 bool JNIHandles::is_frame_handle(JavaThread* thr, jobject obj) {
162 // If there is no java frame, then this must be top level code, such
163 // as the java command executable, in which case, this type of handle
164 // is not permitted.
165 return (thr->has_last_Java_frame() &&
166 (void*)obj < (void*)thr->stack_base() &&
167 (void*)obj >= (void*)thr->last_Java_sp());
168 }
171 bool JNIHandles::is_global_handle(jobject handle) {
172 return _global_handles->chain_contains(handle);
173 }
176 bool JNIHandles::is_weak_global_handle(jobject handle) {
177 return _weak_global_handles->chain_contains(handle);
178 }
180 long JNIHandles::global_handle_memory_usage() {
181 return _global_handles->memory_usage();
182 }
184 long JNIHandles::weak_global_handle_memory_usage() {
185 return _weak_global_handles->memory_usage();
186 }
189 class AlwaysAliveClosure: public BoolObjectClosure {
190 public:
191 bool do_object_b(oop obj) { return true; }
192 };
194 class CountHandleClosure: public OopClosure {
195 private:
196 int _count;
197 public:
198 CountHandleClosure(): _count(0) {}
199 virtual void do_oop(oop* unused) {
200 _count++;
201 }
202 virtual void do_oop(narrowOop* unused) { ShouldNotReachHere(); }
203 int count() { return _count; }
204 };
206 // We assume this is called at a safepoint: no lock is needed.
207 void JNIHandles::print_on(outputStream* st) {
208 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
209 assert(_global_handles != NULL && _weak_global_handles != NULL,
210 "JNIHandles not initialized");
212 CountHandleClosure global_handle_count;
213 AlwaysAliveClosure always_alive;
214 oops_do(&global_handle_count);
215 weak_oops_do(&always_alive, &global_handle_count);
217 st->print_cr("JNI global references: %d", global_handle_count.count());
218 st->cr();
219 st->flush();
220 }
222 class VerifyHandleClosure: public OopClosure {
223 public:
224 virtual void do_oop(oop* root) {
225 (*root)->verify();
226 }
227 virtual void do_oop(narrowOop* root) { ShouldNotReachHere(); }
228 };
230 void JNIHandles::verify() {
231 VerifyHandleClosure verify_handle;
232 AlwaysAliveClosure always_alive;
234 oops_do(&verify_handle);
235 weak_oops_do(&always_alive, &verify_handle);
236 }
240 void jni_handles_init() {
241 JNIHandles::initialize();
242 }
245 int JNIHandleBlock::_blocks_allocated = 0;
246 JNIHandleBlock* JNIHandleBlock::_block_free_list = NULL;
247 #ifndef PRODUCT
248 JNIHandleBlock* JNIHandleBlock::_block_list = NULL;
249 #endif
252 void JNIHandleBlock::zap() {
253 // Zap block values
254 _top = 0;
255 for (int index = 0; index < block_size_in_oops; index++) {
256 _handles[index] = badJNIHandle;
257 }
258 }
260 JNIHandleBlock* JNIHandleBlock::allocate_block(Thread* thread) {
261 assert(thread == NULL || thread == Thread::current(), "sanity check");
262 JNIHandleBlock* block;
263 // Check the thread-local free list for a block so we don't
264 // have to acquire a mutex.
265 if (thread != NULL && thread->free_handle_block() != NULL) {
266 block = thread->free_handle_block();
267 thread->set_free_handle_block(block->_next);
268 }
269 else {
270 // locking with safepoint checking introduces a potential deadlock:
271 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock
272 // - another would hold Threads_lock (jni_AttachCurrentThread) and then
273 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)
274 MutexLockerEx ml(JNIHandleBlockFreeList_lock,
275 Mutex::_no_safepoint_check_flag);
276 if (_block_free_list == NULL) {
277 // Allocate new block
278 block = new JNIHandleBlock();
279 _blocks_allocated++;
280 if (TraceJNIHandleAllocation) {
281 tty->print_cr("JNIHandleBlock " INTPTR_FORMAT " allocated (%d total blocks)",
282 block, _blocks_allocated);
283 }
284 if (ZapJNIHandleArea) block->zap();
285 #ifndef PRODUCT
286 // Link new block to list of all allocated blocks
287 block->_block_list_link = _block_list;
288 _block_list = block;
289 #endif
290 } else {
291 // Get block from free list
292 block = _block_free_list;
293 _block_free_list = _block_free_list->_next;
294 }
295 }
296 block->_top = 0;
297 block->_next = NULL;
298 block->_pop_frame_link = NULL;
299 block->_planned_capacity = block_size_in_oops;
300 // _last, _free_list & _allocate_before_rebuild initialized in allocate_handle
301 debug_only(block->_last = NULL);
302 debug_only(block->_free_list = NULL);
303 debug_only(block->_allocate_before_rebuild = -1);
304 return block;
305 }
308 void JNIHandleBlock::release_block(JNIHandleBlock* block, Thread* thread) {
309 assert(thread == NULL || thread == Thread::current(), "sanity check");
310 JNIHandleBlock* pop_frame_link = block->pop_frame_link();
311 // Put returned block at the beginning of the thread-local free list.
312 // Note that if thread == NULL, we use it as an implicit argument that
313 // we _don't_ want the block to be kept on the free_handle_block.
314 // See for instance JavaThread::exit().
315 if (thread != NULL ) {
316 if (ZapJNIHandleArea) block->zap();
317 JNIHandleBlock* freelist = thread->free_handle_block();
318 block->_pop_frame_link = NULL;
319 thread->set_free_handle_block(block);
321 // Add original freelist to end of chain
322 if ( freelist != NULL ) {
323 while ( block->_next != NULL ) block = block->_next;
324 block->_next = freelist;
325 }
326 block = NULL;
327 }
328 if (block != NULL) {
329 // Return blocks to free list
330 // locking with safepoint checking introduces a potential deadlock:
331 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock
332 // - another would hold Threads_lock (jni_AttachCurrentThread) and then
333 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)
334 MutexLockerEx ml(JNIHandleBlockFreeList_lock,
335 Mutex::_no_safepoint_check_flag);
336 while (block != NULL) {
337 if (ZapJNIHandleArea) block->zap();
338 JNIHandleBlock* next = block->_next;
339 block->_next = _block_free_list;
340 _block_free_list = block;
341 block = next;
342 }
343 }
344 if (pop_frame_link != NULL) {
345 // As a sanity check we release blocks pointed to by the pop_frame_link.
346 // This should never happen (only if PopLocalFrame is not called the
347 // correct number of times).
348 release_block(pop_frame_link, thread);
349 }
350 }
353 void JNIHandleBlock::oops_do(OopClosure* f) {
354 JNIHandleBlock* current_chain = this;
355 // Iterate over chain of blocks, followed by chains linked through the
356 // pop frame links.
357 while (current_chain != NULL) {
358 for (JNIHandleBlock* current = current_chain; current != NULL;
359 current = current->_next) {
360 assert(current == current_chain || current->pop_frame_link() == NULL,
361 "only blocks first in chain should have pop frame link set");
362 for (int index = 0; index < current->_top; index++) {
363 oop* root = &(current->_handles)[index];
364 oop value = *root;
365 // traverse heap pointers only, not deleted handles or free list
366 // pointers
367 if (value != NULL && Universe::heap()->is_in_reserved(value)) {
368 f->do_oop(root);
369 }
370 }
371 // the next handle block is valid only if current block is full
372 if (current->_top < block_size_in_oops) {
373 break;
374 }
375 }
376 current_chain = current_chain->pop_frame_link();
377 }
378 }
381 void JNIHandleBlock::weak_oops_do(BoolObjectClosure* is_alive,
382 OopClosure* f) {
383 for (JNIHandleBlock* current = this; current != NULL; current = current->_next) {
384 assert(current->pop_frame_link() == NULL,
385 "blocks holding weak global JNI handles should not have pop frame link set");
386 for (int index = 0; index < current->_top; index++) {
387 oop* root = &(current->_handles)[index];
388 oop value = *root;
389 // traverse heap pointers only, not deleted handles or free list pointers
390 if (value != NULL && Universe::heap()->is_in_reserved(value)) {
391 if (is_alive->do_object_b(value)) {
392 // The weakly referenced object is alive, update pointer
393 f->do_oop(root);
394 } else {
395 // The weakly referenced object is not alive, clear the reference by storing NULL
396 if (TraceReferenceGC) {
397 tty->print_cr("Clearing JNI weak reference (" INTPTR_FORMAT ")", root);
398 }
399 *root = NULL;
400 }
401 }
402 }
403 // the next handle block is valid only if current block is full
404 if (current->_top < block_size_in_oops) {
405 break;
406 }
407 }
409 /*
410 * JVMTI data structures may also contain weak oops. The iteration of them
411 * is placed here so that we don't need to add it to each of the collectors.
412 */
413 JvmtiExport::weak_oops_do(is_alive, f);
414 }
417 jobject JNIHandleBlock::allocate_handle(oop obj) {
418 assert(Universe::heap()->is_in_reserved(obj), "sanity check");
419 if (_top == 0) {
420 // This is the first allocation or the initial block got zapped when
421 // entering a native function. If we have any following blocks they are
422 // not valid anymore.
423 for (JNIHandleBlock* current = _next; current != NULL;
424 current = current->_next) {
425 assert(current->_last == NULL, "only first block should have _last set");
426 assert(current->_free_list == NULL,
427 "only first block should have _free_list set");
428 current->_top = 0;
429 if (ZapJNIHandleArea) current->zap();
430 }
431 // Clear initial block
432 _free_list = NULL;
433 _allocate_before_rebuild = 0;
434 _last = this;
435 if (ZapJNIHandleArea) zap();
436 }
438 // Try last block
439 if (_last->_top < block_size_in_oops) {
440 oop* handle = &(_last->_handles)[_last->_top++];
441 *handle = obj;
442 return (jobject) handle;
443 }
445 // Try free list
446 if (_free_list != NULL) {
447 oop* handle = _free_list;
448 _free_list = (oop*) *_free_list;
449 *handle = obj;
450 return (jobject) handle;
451 }
452 // Check if unused block follow last
453 if (_last->_next != NULL) {
454 // update last and retry
455 _last = _last->_next;
456 return allocate_handle(obj);
457 }
459 // No space available, we have to rebuild free list or expand
460 if (_allocate_before_rebuild == 0) {
461 rebuild_free_list(); // updates _allocate_before_rebuild counter
462 } else {
463 // Append new block
464 Thread* thread = Thread::current();
465 Handle obj_handle(thread, obj);
466 // This can block, so we need to preserve obj accross call.
467 _last->_next = JNIHandleBlock::allocate_block(thread);
468 _last = _last->_next;
469 _allocate_before_rebuild--;
470 obj = obj_handle();
471 }
472 return allocate_handle(obj); // retry
473 }
476 void JNIHandleBlock::rebuild_free_list() {
477 assert(_allocate_before_rebuild == 0 && _free_list == NULL, "just checking");
478 int free = 0;
479 int blocks = 0;
480 for (JNIHandleBlock* current = this; current != NULL; current = current->_next) {
481 for (int index = 0; index < current->_top; index++) {
482 oop* handle = &(current->_handles)[index];
483 if (*handle == JNIHandles::deleted_handle()) {
484 // this handle was cleared out by a delete call, reuse it
485 *handle = (oop) _free_list;
486 _free_list = handle;
487 free++;
488 }
489 }
490 // we should not rebuild free list if there are unused handles at the end
491 assert(current->_top == block_size_in_oops, "just checking");
492 blocks++;
493 }
494 // Heuristic: if more than half of the handles are free we rebuild next time
495 // as well, otherwise we append a corresponding number of new blocks before
496 // attempting a free list rebuild again.
497 int total = blocks * block_size_in_oops;
498 int extra = total - 2*free;
499 if (extra > 0) {
500 // Not as many free handles as we would like - compute number of new blocks to append
501 _allocate_before_rebuild = (extra + block_size_in_oops - 1) / block_size_in_oops;
502 }
503 if (TraceJNIHandleAllocation) {
504 tty->print_cr("Rebuild free list JNIHandleBlock " INTPTR_FORMAT " blocks=%d used=%d free=%d add=%d",
505 this, blocks, total-free, free, _allocate_before_rebuild);
506 }
507 }
510 bool JNIHandleBlock::contains(jobject handle) const {
511 return ((jobject)&_handles[0] <= handle && handle<(jobject)&_handles[_top]);
512 }
515 bool JNIHandleBlock::chain_contains(jobject handle) const {
516 for (JNIHandleBlock* current = (JNIHandleBlock*) this; current != NULL; current = current->_next) {
517 if (current->contains(handle)) {
518 return true;
519 }
520 }
521 return false;
522 }
525 int JNIHandleBlock::length() const {
526 int result = 1;
527 for (JNIHandleBlock* current = _next; current != NULL; current = current->_next) {
528 result++;
529 }
530 return result;
531 }
533 const size_t JNIHandleBlock::get_number_of_live_handles() {
534 CountHandleClosure counter;
535 oops_do(&counter);
536 return counter.count();
537 }
539 // This method is not thread-safe, i.e., must be called whule holding a lock on the
540 // structure.
541 long JNIHandleBlock::memory_usage() const {
542 return length() * sizeof(JNIHandleBlock);
543 }
546 #ifndef PRODUCT
548 bool JNIHandleBlock::any_contains(jobject handle) {
549 for (JNIHandleBlock* current = _block_list; current != NULL; current = current->_block_list_link) {
550 if (current->contains(handle)) {
551 return true;
552 }
553 }
554 return false;
555 }
557 void JNIHandleBlock::print_statistics() {
558 int used_blocks = 0;
559 int free_blocks = 0;
560 int used_handles = 0;
561 int free_handles = 0;
562 JNIHandleBlock* block = _block_list;
563 while (block != NULL) {
564 if (block->_top > 0) {
565 used_blocks++;
566 } else {
567 free_blocks++;
568 }
569 used_handles += block->_top;
570 free_handles += (block_size_in_oops - block->_top);
571 block = block->_block_list_link;
572 }
573 tty->print_cr("JNIHandleBlocks statistics");
574 tty->print_cr("- blocks allocated: %d", used_blocks + free_blocks);
575 tty->print_cr("- blocks in use: %d", used_blocks);
576 tty->print_cr("- blocks free: %d", free_blocks);
577 tty->print_cr("- handles in use: %d", used_handles);
578 tty->print_cr("- handles free: %d", free_handles);
579 }
581 #endif