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