1 /* 2 * Copyright (c) 1998, 2017, 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 "classfile/systemDictionary.hpp" 27 #include "logging/log.hpp" 28 #include "memory/iterator.hpp" 29 #include "oops/oop.inline.hpp" 30 #include "runtime/jniHandles.hpp" 31 #include "runtime/mutexLocker.hpp" 32 #include "runtime/thread.inline.hpp" 33 #include "trace/traceMacros.hpp" 34 #include "utilities/align.hpp" 35 #if INCLUDE_ALL_GCS 36 #include "gc/g1/g1SATBCardTableModRefBS.hpp" 37 #endif 38 39 JNIHandleBlock* JNIHandles::_global_handles = NULL; 40 JNIHandleBlock* JNIHandles::_weak_global_handles = NULL; 41 oop JNIHandles::_deleted_handle = NULL; 42 43 44 jobject JNIHandles::make_local(oop obj) { 45 if (obj == NULL) { 46 return NULL; // ignore null handles 47 } else { 48 Thread* thread = Thread::current(); 49 assert(Universe::heap()->is_in_reserved(obj), "sanity check"); 50 assert(JavaThread::current()->thread_state() != _thread_in_native, "must not be in native"); 51 return thread->active_handles()->allocate_handle(obj); 52 } 53 } 54 55 56 // optimized versions 57 58 jobject JNIHandles::make_local(Thread* thread, oop obj) { 59 if (obj == NULL) { 60 return NULL; // ignore null handles 61 } else { 62 assert(Universe::heap()->is_in_reserved(obj), "sanity check"); 63 assert(thread->is_Java_thread(), "not a Java thread"); 64 assert(((JavaThread *)thread)->thread_state() != _thread_in_native, "must not be in native"); 65 return thread->active_handles()->allocate_handle(obj); 66 } 67 } 68 69 70 jobject JNIHandles::make_local(JNIEnv* env, oop obj) { 71 if (obj == NULL) { 72 return NULL; // ignore null handles 73 } else { 74 JavaThread* thread = JavaThread::thread_from_jni_environment(env); 75 assert(Universe::heap()->is_in_reserved(obj), "sanity check"); 76 assert(thread->thread_state() != _thread_in_native, "must not be in native"); 77 return thread->active_handles()->allocate_handle(obj); 78 } 79 } 80 81 82 jobject JNIHandles::make_global(Handle obj) { 83 assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC"); 84 assert(JavaThread::current()->thread_state() != _thread_in_native, "must not be in native"); 85 jobject res = NULL; 86 if (!obj.is_null()) { 87 // ignore null handles 88 MutexLocker ml(JNIGlobalHandle_lock); 89 assert(Universe::heap()->is_in_reserved(obj()), "sanity check"); 90 res = _global_handles->allocate_handle(obj()); 91 } else { 92 CHECK_UNHANDLED_OOPS_ONLY(Thread::current()->clear_unhandled_oops()); 93 } 94 95 return res; 96 } 97 98 99 jobject JNIHandles::make_weak_global(Handle obj) { 100 assert(!Universe::heap()->is_gc_active(), "can't extend the root set during GC"); 101 assert(JavaThread::current()->thread_state() != _thread_in_native, "must not be in native"); 102 jobject res = NULL; 103 if (!obj.is_null()) { 104 // ignore null handles 105 { 106 MutexLocker ml(JNIGlobalHandle_lock); 107 assert(Universe::heap()->is_in_reserved(obj()), "sanity check"); 108 res = _weak_global_handles->allocate_handle(obj()); 109 } 110 // Add weak tag. 111 assert(is_aligned(res, weak_tag_alignment), "invariant"); 112 char* tptr = reinterpret_cast<char*>(res) + weak_tag_value; 113 res = reinterpret_cast<jobject>(tptr); 114 } else { 115 CHECK_UNHANDLED_OOPS_ONLY(Thread::current()->clear_unhandled_oops()); 116 } 117 return res; 118 } 119 120 template<bool external_guard> 121 oop JNIHandles::resolve_jweak(jweak handle) { 122 assert(is_jweak(handle), "precondition"); 123 oop result = jweak_ref(handle); 124 result = guard_value<external_guard>(result); 125 #if INCLUDE_ALL_GCS 126 if (result != NULL && UseG1GC) { 127 G1SATBCardTableModRefBS::enqueue(result); 128 } 129 #endif // INCLUDE_ALL_GCS 130 return result; 131 } 132 133 template oop JNIHandles::resolve_jweak<true>(jweak); 134 template oop JNIHandles::resolve_jweak<false>(jweak); 135 136 bool JNIHandles::is_global_weak_cleared(jweak handle) { 137 assert(is_jweak(handle), "not a weak handle"); 138 return guard_value<false>(jweak_ref(handle)) == NULL; 139 } 140 141 void JNIHandles::destroy_global(jobject handle) { 142 if (handle != NULL) { 143 assert(is_global_handle(handle), "Invalid delete of global JNI handle"); 144 jobject_ref(handle) = deleted_handle(); 145 } 146 } 147 148 149 void JNIHandles::destroy_weak_global(jobject handle) { 150 if (handle != NULL) { 151 jweak_ref(handle) = deleted_handle(); 152 } 153 } 154 155 156 void JNIHandles::oops_do(OopClosure* f) { 157 f->do_oop(&_deleted_handle); 158 _global_handles->oops_do(f); 159 } 160 161 162 void JNIHandles::weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f) { 163 _weak_global_handles->weak_oops_do(is_alive, f); 164 } 165 166 167 void JNIHandles::weak_oops_do(OopClosure* f) { 168 AlwaysTrueClosure always_true; 169 weak_oops_do(&always_true, f); 170 } 171 172 173 void JNIHandles::initialize() { 174 _global_handles = JNIHandleBlock::allocate_block(); 175 _weak_global_handles = JNIHandleBlock::allocate_block(); 176 EXCEPTION_MARK; 177 // We will never reach the CATCH below since Exceptions::_throw will cause 178 // the VM to exit if an exception is thrown during initialization 179 Klass* k = SystemDictionary::Object_klass(); 180 _deleted_handle = InstanceKlass::cast(k)->allocate_instance(CATCH); 181 } 182 183 184 bool JNIHandles::is_local_handle(Thread* thread, jobject handle) { 185 JNIHandleBlock* block = thread->active_handles(); 186 187 // Look back past possible native calls to jni_PushLocalFrame. 188 while (block != NULL) { 189 if (block->chain_contains(handle)) { 190 return true; 191 } 192 block = block->pop_frame_link(); 193 } 194 return false; 195 } 196 197 198 // Determine if the handle is somewhere in the current thread's stack. 199 // We easily can't isolate any particular stack frame the handle might 200 // come from, so we'll check the whole stack. 201 202 bool JNIHandles::is_frame_handle(JavaThread* thr, jobject obj) { 203 // If there is no java frame, then this must be top level code, such 204 // as the java command executable, in which case, this type of handle 205 // is not permitted. 206 return (thr->has_last_Java_frame() && 207 (void*)obj < (void*)thr->stack_base() && 208 (void*)obj >= (void*)thr->last_Java_sp()); 209 } 210 211 212 bool JNIHandles::is_global_handle(jobject handle) { 213 return _global_handles->chain_contains(handle); 214 } 215 216 217 bool JNIHandles::is_weak_global_handle(jobject handle) { 218 return _weak_global_handles->chain_contains(handle); 219 } 220 221 long JNIHandles::global_handle_memory_usage() { 222 return _global_handles->memory_usage(); 223 } 224 225 long JNIHandles::weak_global_handle_memory_usage() { 226 return _weak_global_handles->memory_usage(); 227 } 228 229 230 class CountHandleClosure: public OopClosure { 231 private: 232 int _count; 233 public: 234 CountHandleClosure(): _count(0) {} 235 virtual void do_oop(oop* ooph) { 236 if (*ooph != JNIHandles::deleted_handle()) { 237 _count++; 238 } 239 } 240 virtual void do_oop(narrowOop* unused) { ShouldNotReachHere(); } 241 int count() { return _count; } 242 }; 243 244 // We assume this is called at a safepoint: no lock is needed. 245 void JNIHandles::print_on(outputStream* st) { 246 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint"); 247 assert(_global_handles != NULL && _weak_global_handles != NULL, 248 "JNIHandles not initialized"); 249 250 CountHandleClosure global_handle_count; 251 oops_do(&global_handle_count); 252 weak_oops_do(&global_handle_count); 253 254 st->print_cr("JNI global references: %d", global_handle_count.count()); 255 st->cr(); 256 st->flush(); 257 } 258 259 class VerifyHandleClosure: public OopClosure { 260 public: 261 virtual void do_oop(oop* root) { 262 (*root)->verify(); 263 } 264 virtual void do_oop(narrowOop* root) { ShouldNotReachHere(); } 265 }; 266 267 void JNIHandles::verify() { 268 VerifyHandleClosure verify_handle; 269 270 oops_do(&verify_handle); 271 weak_oops_do(&verify_handle); 272 } 273 274 275 276 void jni_handles_init() { 277 JNIHandles::initialize(); 278 } 279 280 281 int JNIHandleBlock::_blocks_allocated = 0; 282 JNIHandleBlock* JNIHandleBlock::_block_free_list = NULL; 283 #ifndef PRODUCT 284 JNIHandleBlock* JNIHandleBlock::_block_list = NULL; 285 #endif 286 287 288 void JNIHandleBlock::zap() { 289 // Zap block values 290 _top = 0; 291 for (int index = 0; index < block_size_in_oops; index++) { 292 _handles[index] = badJNIHandle; 293 } 294 } 295 296 JNIHandleBlock* JNIHandleBlock::allocate_block(Thread* thread) { 297 assert(thread == NULL || thread == Thread::current(), "sanity check"); 298 JNIHandleBlock* block; 299 // Check the thread-local free list for a block so we don't 300 // have to acquire a mutex. 301 if (thread != NULL && thread->free_handle_block() != NULL) { 302 block = thread->free_handle_block(); 303 thread->set_free_handle_block(block->_next); 304 } 305 else { 306 // locking with safepoint checking introduces a potential deadlock: 307 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock 308 // - another would hold Threads_lock (jni_AttachCurrentThread) and then 309 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block) 310 MutexLockerEx ml(JNIHandleBlockFreeList_lock, 311 Mutex::_no_safepoint_check_flag); 312 if (_block_free_list == NULL) { 313 // Allocate new block 314 block = new JNIHandleBlock(); 315 _blocks_allocated++; 316 if (ZapJNIHandleArea) block->zap(); 317 #ifndef PRODUCT 318 // Link new block to list of all allocated blocks 319 block->_block_list_link = _block_list; 320 _block_list = block; 321 #endif 322 } else { 323 // Get block from free list 324 block = _block_free_list; 325 _block_free_list = _block_free_list->_next; 326 } 327 } 328 block->_top = 0; 329 block->_next = NULL; 330 block->_pop_frame_link = NULL; 331 block->_planned_capacity = block_size_in_oops; 332 // _last, _free_list & _allocate_before_rebuild initialized in allocate_handle 333 debug_only(block->_last = NULL); 334 debug_only(block->_free_list = NULL); 335 debug_only(block->_allocate_before_rebuild = -1); 336 return block; 337 } 338 339 340 void JNIHandleBlock::release_block(JNIHandleBlock* block, Thread* thread) { 341 assert(thread == NULL || thread == Thread::current(), "sanity check"); 342 JNIHandleBlock* pop_frame_link = block->pop_frame_link(); 343 // Put returned block at the beginning of the thread-local free list. 344 // Note that if thread == NULL, we use it as an implicit argument that 345 // we _don't_ want the block to be kept on the free_handle_block. 346 // See for instance JavaThread::exit(). 347 if (thread != NULL ) { 348 if (ZapJNIHandleArea) block->zap(); 349 JNIHandleBlock* freelist = thread->free_handle_block(); 350 block->_pop_frame_link = NULL; 351 thread->set_free_handle_block(block); 352 353 // Add original freelist to end of chain 354 if ( freelist != NULL ) { 355 while ( block->_next != NULL ) block = block->_next; 356 block->_next = freelist; 357 } 358 block = NULL; 359 } 360 if (block != NULL) { 361 // Return blocks to free list 362 // locking with safepoint checking introduces a potential deadlock: 363 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock 364 // - another would hold Threads_lock (jni_AttachCurrentThread) and then 365 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block) 366 MutexLockerEx ml(JNIHandleBlockFreeList_lock, 367 Mutex::_no_safepoint_check_flag); 368 while (block != NULL) { 369 if (ZapJNIHandleArea) block->zap(); 370 JNIHandleBlock* next = block->_next; 371 block->_next = _block_free_list; 372 _block_free_list = block; 373 block = next; 374 } 375 } 376 if (pop_frame_link != NULL) { 377 // As a sanity check we release blocks pointed to by the pop_frame_link. 378 // This should never happen (only if PopLocalFrame is not called the 379 // correct number of times). 380 release_block(pop_frame_link, thread); 381 } 382 } 383 384 385 void JNIHandleBlock::oops_do(OopClosure* f) { 386 JNIHandleBlock* current_chain = this; 387 // Iterate over chain of blocks, followed by chains linked through the 388 // pop frame links. 389 while (current_chain != NULL) { 390 for (JNIHandleBlock* current = current_chain; current != NULL; 391 current = current->_next) { 392 assert(current == current_chain || current->pop_frame_link() == NULL, 393 "only blocks first in chain should have pop frame link set"); 394 for (int index = 0; index < current->_top; index++) { 395 oop* root = &(current->_handles)[index]; 396 oop value = *root; 397 // traverse heap pointers only, not deleted handles or free list 398 // pointers 399 if (value != NULL && Universe::heap()->is_in_reserved(value)) { 400 f->do_oop(root); 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 } 408 current_chain = current_chain->pop_frame_link(); 409 } 410 } 411 412 413 void JNIHandleBlock::weak_oops_do(BoolObjectClosure* is_alive, 414 OopClosure* f) { 415 for (JNIHandleBlock* current = this; current != NULL; current = current->_next) { 416 assert(current->pop_frame_link() == NULL, 417 "blocks holding weak global JNI handles should not have pop frame link set"); 418 for (int index = 0; index < current->_top; index++) { 419 oop* root = &(current->_handles)[index]; 420 oop value = *root; 421 // traverse heap pointers only, not deleted handles or free list pointers 422 if (value != NULL && Universe::heap()->is_in_reserved(value)) { 423 if (is_alive->do_object_b(value)) { 424 // The weakly referenced object is alive, update pointer 425 f->do_oop(root); 426 } else { 427 // The weakly referenced object is not alive, clear the reference by storing NULL 428 log_develop_trace(gc, ref)("Clearing JNI weak reference (" INTPTR_FORMAT ")", p2i(root)); 429 *root = NULL; 430 } 431 } 432 } 433 // the next handle block is valid only if current block is full 434 if (current->_top < block_size_in_oops) { 435 break; 436 } 437 } 438 } 439 440 441 jobject JNIHandleBlock::allocate_handle(oop obj) { 442 assert(Universe::heap()->is_in_reserved(obj), "sanity check"); 443 if (_top == 0) { 444 // This is the first allocation or the initial block got zapped when 445 // entering a native function. If we have any following blocks they are 446 // not valid anymore. 447 for (JNIHandleBlock* current = _next; current != NULL; 448 current = current->_next) { 449 assert(current->_last == NULL, "only first block should have _last set"); 450 assert(current->_free_list == NULL, 451 "only first block should have _free_list set"); 452 if (current->_top == 0) { 453 // All blocks after the first clear trailing block are already cleared. 454 #ifdef ASSERT 455 for (current = current->_next; current != NULL; current = current->_next) { 456 assert(current->_top == 0, "trailing blocks must already be cleared"); 457 } 458 #endif 459 break; 460 } 461 current->_top = 0; 462 if (ZapJNIHandleArea) current->zap(); 463 } 464 // Clear initial block 465 _free_list = NULL; 466 _allocate_before_rebuild = 0; 467 _last = this; 468 if (ZapJNIHandleArea) zap(); 469 } 470 471 // Try last block 472 if (_last->_top < block_size_in_oops) { 473 oop* handle = &(_last->_handles)[_last->_top++]; 474 *handle = obj; 475 return (jobject) handle; 476 } 477 478 // Try free list 479 if (_free_list != NULL) { 480 oop* handle = _free_list; 481 _free_list = (oop*) *_free_list; 482 *handle = obj; 483 return (jobject) handle; 484 } 485 // Check if unused block follow last 486 if (_last->_next != NULL) { 487 // update last and retry 488 _last = _last->_next; 489 return allocate_handle(obj); 490 } 491 492 // No space available, we have to rebuild free list or expand 493 if (_allocate_before_rebuild == 0) { 494 rebuild_free_list(); // updates _allocate_before_rebuild counter 495 } else { 496 // Append new block 497 Thread* thread = Thread::current(); 498 Handle obj_handle(thread, obj); 499 // This can block, so we need to preserve obj across call. 500 _last->_next = JNIHandleBlock::allocate_block(thread); 501 _last = _last->_next; 502 _allocate_before_rebuild--; 503 obj = obj_handle(); 504 } 505 return allocate_handle(obj); // retry 506 } 507 508 void JNIHandleBlock::release_handle(jobject h) { 509 if (h != NULL) { 510 assert(chain_contains(h), "does not contain the JNI handle"); 511 // Mark the handle as deleted, allocate will reuse it 512 *((oop*)h) = JNIHandles::deleted_handle(); 513 } 514 } 515 516 517 void JNIHandleBlock::rebuild_free_list() { 518 assert(_allocate_before_rebuild == 0 && _free_list == NULL, "just checking"); 519 int free = 0; 520 int blocks = 0; 521 for (JNIHandleBlock* current = this; current != NULL; current = current->_next) { 522 for (int index = 0; index < current->_top; index++) { 523 oop* handle = &(current->_handles)[index]; 524 if (*handle == JNIHandles::deleted_handle()) { 525 // this handle was cleared out by a delete call, reuse it 526 *handle = (oop) _free_list; 527 _free_list = handle; 528 free++; 529 } 530 } 531 // we should not rebuild free list if there are unused handles at the end 532 assert(current->_top == block_size_in_oops, "just checking"); 533 blocks++; 534 } 535 // Heuristic: if more than half of the handles are free we rebuild next time 536 // as well, otherwise we append a corresponding number of new blocks before 537 // attempting a free list rebuild again. 538 int total = blocks * block_size_in_oops; 539 int extra = total - 2*free; 540 if (extra > 0) { 541 // Not as many free handles as we would like - compute number of new blocks to append 542 _allocate_before_rebuild = (extra + block_size_in_oops - 1) / block_size_in_oops; 543 } 544 } 545 546 547 bool JNIHandleBlock::contains(jobject handle) const { 548 return ((jobject)&_handles[0] <= handle && handle<(jobject)&_handles[_top]); 549 } 550 551 552 bool JNIHandleBlock::chain_contains(jobject handle) const { 553 for (JNIHandleBlock* current = (JNIHandleBlock*) this; current != NULL; current = current->_next) { 554 if (current->contains(handle)) { 555 return true; 556 } 557 } 558 return false; 559 } 560 561 562 int JNIHandleBlock::length() const { 563 int result = 1; 564 for (JNIHandleBlock* current = _next; current != NULL; current = current->_next) { 565 result++; 566 } 567 return result; 568 } 569 570 const size_t JNIHandleBlock::get_number_of_live_handles() { 571 CountHandleClosure counter; 572 oops_do(&counter); 573 return counter.count(); 574 } 575 576 // This method is not thread-safe, i.e., must be called while holding a lock on the 577 // structure. 578 long JNIHandleBlock::memory_usage() const { 579 return length() * sizeof(JNIHandleBlock); 580 } 581 582 583 #ifndef PRODUCT 584 585 bool JNIHandleBlock::any_contains(jobject handle) { 586 for (JNIHandleBlock* current = _block_list; current != NULL; current = current->_block_list_link) { 587 if (current->contains(handle)) { 588 return true; 589 } 590 } 591 return false; 592 } 593 594 void JNIHandleBlock::print_statistics() { 595 int used_blocks = 0; 596 int free_blocks = 0; 597 int used_handles = 0; 598 int free_handles = 0; 599 JNIHandleBlock* block = _block_list; 600 while (block != NULL) { 601 if (block->_top > 0) { 602 used_blocks++; 603 } else { 604 free_blocks++; 605 } 606 used_handles += block->_top; 607 free_handles += (block_size_in_oops - block->_top); 608 block = block->_block_list_link; 609 } 610 tty->print_cr("JNIHandleBlocks statistics"); 611 tty->print_cr("- blocks allocated: %d", used_blocks + free_blocks); 612 tty->print_cr("- blocks in use: %d", used_blocks); 613 tty->print_cr("- blocks free: %d", free_blocks); 614 tty->print_cr("- handles in use: %d", used_handles); 615 tty->print_cr("- handles free: %d", free_handles); 616 } 617 618 #endif