1 /* 2 * Copyright (c) 1998, 2022, 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/collectedHeap.hpp" 27 #include "gc/shared/oopStorage.inline.hpp" 28 #include "gc/shared/oopStorageSet.hpp" 29 #include "logging/log.hpp" 30 #include "memory/iterator.hpp" 31 #include "memory/universe.hpp" 32 #include "oops/access.inline.hpp" 33 #include "oops/oop.inline.hpp" 34 #include "runtime/handles.inline.hpp" 35 #include "runtime/jniHandles.inline.hpp" 36 #include "runtime/mutexLocker.hpp" 37 #include "runtime/thread.inline.hpp" 38 #include "utilities/align.hpp" 39 #include "utilities/debug.hpp" 40 41 OopStorage* JNIHandles::global_handles() { 42 return _global_handles; 43 } 44 45 OopStorage* JNIHandles::weak_global_handles() { 46 return _weak_global_handles; 47 } 48 49 // Serviceability agent support. 50 OopStorage* JNIHandles::_global_handles = NULL; 51 OopStorage* JNIHandles::_weak_global_handles = NULL; 52 53 void jni_handles_init() { 54 JNIHandles::_global_handles = OopStorageSet::create_strong("JNI Global", mtInternal); 55 JNIHandles::_weak_global_handles = OopStorageSet::create_weak("JNI Weak", mtInternal); 56 } 57 58 jobject JNIHandles::make_local(oop obj) { 59 return make_local(JavaThread::current(), obj); 60 } 61 62 // Used by NewLocalRef which requires NULL on out-of-memory 63 jobject JNIHandles::make_local(JavaThread* thread, oop obj, AllocFailType alloc_failmode) { 64 if (obj == NULL) { 65 return NULL; // ignore null handles 66 } else { 67 assert(oopDesc::is_oop(obj), "not an oop"); 68 assert(!current_thread_in_native(), "must not be in native"); 69 return thread->active_handles()->allocate_handle(thread, 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(OopClosure* f) { 172 weak_global_handles()->weak_oops_do(f); 173 } 174 175 bool JNIHandles::is_global_storage(const OopStorage* storage) { 176 return _global_handles == storage; 177 } 178 179 inline bool is_storage_handle(const OopStorage* storage, const oop* ptr) { 180 return storage->allocation_status(ptr) == OopStorage::ALLOCATED_ENTRY; 181 } 182 183 184 jobjectRefType JNIHandles::handle_type(JavaThread* thread, jobject handle) { 185 assert(handle != NULL, "precondition"); 186 jobjectRefType result = JNIInvalidRefType; 187 if (is_jweak(handle)) { 188 if (is_storage_handle(weak_global_handles(), jweak_ptr(handle))) { 189 result = JNIWeakGlobalRefType; 190 } 191 } else { 192 switch (global_handles()->allocation_status(jobject_ptr(handle))) { 193 case OopStorage::ALLOCATED_ENTRY: 194 result = JNIGlobalRefType; 195 break; 196 197 case OopStorage::UNALLOCATED_ENTRY: 198 break; // Invalid global handle 199 200 case OopStorage::INVALID_ENTRY: 201 // Not in global storage. Might be a local handle. 202 if (is_local_handle(thread, handle) || is_frame_handle(thread, handle)) { 203 result = JNILocalRefType; 204 } 205 break; 206 207 default: 208 ShouldNotReachHere(); 209 } 210 } 211 return result; 212 } 213 214 215 bool JNIHandles::is_local_handle(JavaThread* thread, jobject handle) { 216 assert(handle != NULL, "precondition"); 217 JNIHandleBlock* block = thread->active_handles(); 218 219 // Look back past possible native calls to jni_PushLocalFrame. 220 while (block != NULL) { 221 if (block->chain_contains(handle)) { 222 return true; 223 } 224 block = block->pop_frame_link(); 225 } 226 return false; 227 } 228 229 230 // Determine if the handle is somewhere in the current thread's stack. 231 // We easily can't isolate any particular stack frame the handle might 232 // come from, so we'll check the whole stack. 233 234 bool JNIHandles::is_frame_handle(JavaThread* thr, jobject handle) { 235 assert(handle != NULL, "precondition"); 236 // If there is no java frame, then this must be top level code, such 237 // as the java command executable, in which case, this type of handle 238 // is not permitted. 239 return (thr->has_last_Java_frame() && 240 thr->is_in_stack_range_incl((address)handle, (address)thr->last_Java_sp())); 241 } 242 243 244 bool JNIHandles::is_global_handle(jobject handle) { 245 assert(handle != NULL, "precondition"); 246 return !is_jweak(handle) && is_storage_handle(global_handles(), jobject_ptr(handle)); 247 } 248 249 250 bool JNIHandles::is_weak_global_handle(jobject handle) { 251 assert(handle != NULL, "precondition"); 252 return is_jweak(handle) && is_storage_handle(weak_global_handles(), jweak_ptr(handle)); 253 } 254 255 size_t JNIHandles::global_handle_memory_usage() { 256 return global_handles()->total_memory_usage(); 257 } 258 259 size_t JNIHandles::weak_global_handle_memory_usage() { 260 return weak_global_handles()->total_memory_usage(); 261 } 262 263 264 // We assume this is called at a safepoint: no lock is needed. 265 void JNIHandles::print_on(outputStream* st) { 266 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint"); 267 268 st->print_cr("JNI global refs: " SIZE_FORMAT ", weak refs: " SIZE_FORMAT, 269 global_handles()->allocation_count(), 270 weak_global_handles()->allocation_count()); 271 st->cr(); 272 st->flush(); 273 } 274 275 void JNIHandles::print() { print_on(tty); } 276 277 class VerifyJNIHandles: public OopClosure { 278 public: 279 virtual void do_oop(oop* root) { 280 guarantee(oopDesc::is_oop_or_null(RawAccess<>::oop_load(root)), "Invalid oop"); 281 } 282 virtual void do_oop(narrowOop* root) { ShouldNotReachHere(); } 283 }; 284 285 void JNIHandles::verify() { 286 VerifyJNIHandles verify_handle; 287 288 oops_do(&verify_handle); 289 weak_oops_do(&verify_handle); 290 } 291 292 // This method is implemented here to avoid circular includes between 293 // jniHandles.hpp and thread.hpp. 294 bool JNIHandles::current_thread_in_native() { 295 Thread* thread = Thread::current(); 296 return (thread->is_Java_thread() && 297 JavaThread::cast(thread)->thread_state() == _thread_in_native); 298 } 299 300 int JNIHandleBlock::_blocks_allocated = 0; 301 302 static inline bool is_tagged_free_list(uintptr_t value) { 303 return (value & 1u) != 0; 304 } 305 306 static inline uintptr_t tag_free_list(uintptr_t value) { 307 return value | 1u; 308 } 309 310 static inline uintptr_t untag_free_list(uintptr_t value) { 311 return value & ~(uintptr_t)1u; 312 } 313 314 // There is a freelist of handles running through the JNIHandleBlock 315 // with a tagged next pointer, distinguishing these next pointers from 316 // oops. The freelist handling currently relies on the size of oops 317 // being the same as a native pointer. If this ever changes, then 318 // this freelist handling must change too. 319 STATIC_ASSERT(sizeof(oop) == sizeof(uintptr_t)); 320 321 #ifdef ASSERT 322 void JNIHandleBlock::zap() { 323 // Zap block values 324 _top = 0; 325 for (int index = 0; index < block_size_in_oops; index++) { 326 // NOT using Access here; just bare clobbering to NULL, since the 327 // block no longer contains valid oops. 328 _handles[index] = 0; 329 } 330 } 331 #endif // ASSERT 332 333 JNIHandleBlock* JNIHandleBlock::allocate_block(JavaThread* thread, AllocFailType alloc_failmode) { 334 // The VM thread can allocate a handle block in behalf of another thread during a safepoint. 335 assert(thread == NULL || thread == Thread::current() || SafepointSynchronize::is_at_safepoint(), 336 "sanity check"); 337 JNIHandleBlock* block; 338 // Check the thread-local free list for a block so we don't 339 // have to acquire a mutex. 340 if (thread != NULL && thread->free_handle_block() != NULL) { 341 block = thread->free_handle_block(); 342 thread->set_free_handle_block(block->_next); 343 } else { 344 // Allocate new block 345 if (alloc_failmode == AllocFailStrategy::RETURN_NULL) { 346 block = new (std::nothrow) JNIHandleBlock(); 347 if (block == NULL) { 348 return NULL; 349 } 350 } else { 351 block = new JNIHandleBlock(); 352 } 353 Atomic::inc(&_blocks_allocated); 354 block->zap(); 355 } 356 block->_top = 0; 357 block->_next = NULL; 358 block->_pop_frame_link = NULL; 359 block->_planned_capacity = block_size_in_oops; 360 // _last, _free_list & _allocate_before_rebuild initialized in allocate_handle 361 debug_only(block->_last = NULL); 362 debug_only(block->_free_list = NULL); 363 debug_only(block->_allocate_before_rebuild = -1); 364 return block; 365 } 366 367 368 void JNIHandleBlock::release_block(JNIHandleBlock* block, JavaThread* thread) { 369 assert(thread == NULL || thread == Thread::current(), "sanity check"); 370 JNIHandleBlock* pop_frame_link = block->pop_frame_link(); 371 // Put returned block at the beginning of the thread-local free list. 372 // Note that if thread == NULL, we use it as an implicit argument that 373 // we _don't_ want the block to be kept on the free_handle_block. 374 // See for instance JavaThread::exit(). 375 if (thread != NULL ) { 376 block->zap(); 377 JNIHandleBlock* freelist = thread->free_handle_block(); 378 block->_pop_frame_link = NULL; 379 thread->set_free_handle_block(block); 380 381 // Add original freelist to end of chain 382 if ( freelist != NULL ) { 383 while ( block->_next != NULL ) block = block->_next; 384 block->_next = freelist; 385 } 386 block = NULL; 387 } else { 388 DEBUG_ONLY(block->set_pop_frame_link(NULL)); 389 while (block != NULL) { 390 JNIHandleBlock* next = block->_next; 391 Atomic::dec(&_blocks_allocated); 392 assert(block->pop_frame_link() == NULL, "pop_frame_link should be NULL"); 393 delete block; 394 block = next; 395 } 396 } 397 if (pop_frame_link != NULL) { 398 // As a sanity check we release blocks pointed to by the pop_frame_link. 399 // This should never happen (only if PopLocalFrame is not called the 400 // correct number of times). 401 release_block(pop_frame_link, thread); 402 } 403 } 404 405 406 void JNIHandleBlock::oops_do(OopClosure* f) { 407 JNIHandleBlock* current_chain = this; 408 // Iterate over chain of blocks, followed by chains linked through the 409 // pop frame links. 410 while (current_chain != NULL) { 411 for (JNIHandleBlock* current = current_chain; current != NULL; 412 current = current->_next) { 413 assert(current == current_chain || current->pop_frame_link() == NULL, 414 "only blocks first in chain should have pop frame link set"); 415 for (int index = 0; index < current->_top; index++) { 416 uintptr_t* addr = &(current->_handles)[index]; 417 uintptr_t value = *addr; 418 // traverse heap pointers only, not deleted handles or free list 419 // pointers 420 if (value != 0 && !is_tagged_free_list(value)) { 421 oop* root = (oop*)addr; 422 f->do_oop(root); 423 } 424 } 425 // the next handle block is valid only if current block is full 426 if (current->_top < block_size_in_oops) { 427 break; 428 } 429 } 430 current_chain = current_chain->pop_frame_link(); 431 } 432 } 433 434 435 jobject JNIHandleBlock::allocate_handle(JavaThread* caller, oop obj, AllocFailType alloc_failmode) { 436 assert(Universe::heap()->is_in(obj), "sanity check"); 437 if (_top == 0) { 438 // This is the first allocation or the initial block got zapped when 439 // entering a native function. If we have any following blocks they are 440 // not valid anymore. 441 for (JNIHandleBlock* current = _next; current != NULL; 442 current = current->_next) { 443 assert(current->_last == NULL, "only first block should have _last set"); 444 assert(current->_free_list == NULL, 445 "only first block should have _free_list set"); 446 if (current->_top == 0) { 447 // All blocks after the first clear trailing block are already cleared. 448 #ifdef ASSERT 449 for (current = current->_next; current != NULL; current = current->_next) { 450 assert(current->_top == 0, "trailing blocks must already be cleared"); 451 } 452 #endif 453 break; 454 } 455 current->_top = 0; 456 current->zap(); 457 } 458 // Clear initial block 459 _free_list = NULL; 460 _allocate_before_rebuild = 0; 461 _last = this; 462 zap(); 463 } 464 465 // Try last block 466 if (_last->_top < block_size_in_oops) { 467 oop* handle = (oop*)&(_last->_handles)[_last->_top++]; 468 NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, obj); 469 return (jobject) handle; 470 } 471 472 // Try free list 473 if (_free_list != NULL) { 474 oop* handle = (oop*)_free_list; 475 _free_list = (uintptr_t*) untag_free_list(*_free_list); 476 NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, obj); 477 return (jobject) handle; 478 } 479 // Check if unused block follow last 480 if (_last->_next != NULL) { 481 // update last and retry 482 _last = _last->_next; 483 return allocate_handle(caller, obj, alloc_failmode); 484 } 485 486 // No space available, we have to rebuild free list or expand 487 if (_allocate_before_rebuild == 0) { 488 rebuild_free_list(); // updates _allocate_before_rebuild counter 489 } else { 490 _last->_next = JNIHandleBlock::allocate_block(caller, alloc_failmode); 491 if (_last->_next == NULL) { 492 return NULL; 493 } 494 _last = _last->_next; 495 _allocate_before_rebuild--; 496 } 497 return allocate_handle(caller, obj, alloc_failmode); // retry 498 } 499 500 void JNIHandleBlock::rebuild_free_list() { 501 assert(_allocate_before_rebuild == 0 && _free_list == NULL, "just checking"); 502 int free = 0; 503 int blocks = 0; 504 for (JNIHandleBlock* current = this; current != NULL; current = current->_next) { 505 for (int index = 0; index < current->_top; index++) { 506 uintptr_t* handle = &(current->_handles)[index]; 507 if (*handle == 0) { 508 // this handle was cleared out by a delete call, reuse it 509 *handle = _free_list == NULL ? 0 : tag_free_list((uintptr_t)_free_list); 510 _free_list = handle; 511 free++; 512 } 513 } 514 // we should not rebuild free list if there are unused handles at the end 515 assert(current->_top == block_size_in_oops, "just checking"); 516 blocks++; 517 } 518 // Heuristic: if more than half of the handles are free we rebuild next time 519 // as well, otherwise we append a corresponding number of new blocks before 520 // attempting a free list rebuild again. 521 int total = blocks * block_size_in_oops; 522 int extra = total - 2*free; 523 if (extra > 0) { 524 // Not as many free handles as we would like - compute number of new blocks to append 525 _allocate_before_rebuild = (extra + block_size_in_oops - 1) / block_size_in_oops; 526 } 527 } 528 529 530 bool JNIHandleBlock::contains(jobject handle) const { 531 return ((jobject)&_handles[0] <= handle && handle<(jobject)&_handles[_top]); 532 } 533 534 535 bool JNIHandleBlock::chain_contains(jobject handle) const { 536 for (JNIHandleBlock* current = (JNIHandleBlock*) this; current != NULL; current = current->_next) { 537 if (current->contains(handle)) { 538 return true; 539 } 540 } 541 return false; 542 } 543 544 545 size_t JNIHandleBlock::length() const { 546 size_t result = 1; 547 for (JNIHandleBlock* current = _next; current != NULL; current = current->_next) { 548 result++; 549 } 550 return result; 551 } 552 553 class CountJNIHandleClosure: public OopClosure { 554 private: 555 int _count; 556 public: 557 CountJNIHandleClosure(): _count(0) {} 558 virtual void do_oop(oop* ooph) { _count++; } 559 virtual void do_oop(narrowOop* unused) { ShouldNotReachHere(); } 560 int count() { return _count; } 561 }; 562 563 const size_t JNIHandleBlock::get_number_of_live_handles() { 564 CountJNIHandleClosure counter; 565 oops_do(&counter); 566 return counter.count(); 567 } 568 569 // This method is not thread-safe, i.e., must be called while holding a lock on the 570 // structure. 571 size_t JNIHandleBlock::memory_usage() const { 572 return length() * sizeof(JNIHandleBlock); 573 }