jniHandles.cpp revision 196:d1605aabd0a1
1/* 2 * Copyright 1998-2008 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, 20 * CA 95054 USA or visit www.sun.com if you need additional information or 21 * have any questions. 22 * 23 */ 24 25# include "incls/_precompiled.incl" 26# include "incls/_jniHandles.cpp.incl" 27 28 29JNIHandleBlock* JNIHandles::_global_handles = NULL; 30JNIHandleBlock* JNIHandles::_weak_global_handles = NULL; 31oop JNIHandles::_deleted_handle = NULL; 32 33 34jobject JNIHandles::make_local(oop obj) { 35 if (obj == NULL) { 36 return NULL; // ignore null handles 37 } else { 38 Thread* thread = Thread::current(); 39 assert(Universe::heap()->is_in_reserved(obj), "sanity check"); 40 return thread->active_handles()->allocate_handle(obj); 41 } 42} 43 44 45// optimized versions 46 47jobject JNIHandles::make_local(Thread* thread, oop obj) { 48 if (obj == NULL) { 49 return NULL; // ignore null handles 50 } else { 51 assert(Universe::heap()->is_in_reserved(obj), "sanity check"); 52 return thread->active_handles()->allocate_handle(obj); 53 } 54} 55 56 57jobject JNIHandles::make_local(JNIEnv* env, oop obj) { 58 if (obj == NULL) { 59 return NULL; // ignore null handles 60 } else { 61 JavaThread* thread = JavaThread::thread_from_jni_environment(env); 62 assert(Universe::heap()->is_in_reserved(obj), "sanity check"); 63 return thread->active_handles()->allocate_handle(obj); 64 } 65} 66 67 68jobject JNIHandles::make_global(Handle obj) { 69 jobject res = NULL; 70 if (!obj.is_null()) { 71 // ignore null handles 72 MutexLocker ml(JNIGlobalHandle_lock); 73 assert(Universe::heap()->is_in_reserved(obj()), "sanity check"); 74 res = _global_handles->allocate_handle(obj()); 75 } else { 76 CHECK_UNHANDLED_OOPS_ONLY(Thread::current()->clear_unhandled_oops()); 77 } 78 79 return res; 80} 81 82 83jobject JNIHandles::make_weak_global(Handle obj) { 84 jobject res = NULL; 85 if (!obj.is_null()) { 86 // ignore null handles 87 MutexLocker ml(JNIGlobalHandle_lock); 88 assert(Universe::heap()->is_in_reserved(obj()), "sanity check"); 89 res = _weak_global_handles->allocate_handle(obj()); 90 } else { 91 CHECK_UNHANDLED_OOPS_ONLY(Thread::current()->clear_unhandled_oops()); 92 } 93 return res; 94} 95 96jmethodID JNIHandles::make_jmethod_id(methodHandle mh) { 97 return (jmethodID) make_weak_global(mh); 98} 99 100 101 102void JNIHandles::change_method_associated_with_jmethod_id(jmethodID jmid, methodHandle mh) { 103 MutexLocker ml(JNIGlobalHandle_lock); // Is this necessary? 104 Handle obj = (Handle)mh; 105 oop* jobj = (oop*)jmid; 106 *jobj = obj(); 107} 108 109 110void JNIHandles::destroy_global(jobject handle) { 111 if (handle != NULL) { 112 assert(is_global_handle(handle), "Invalid delete of global JNI handle"); 113 *((oop*)handle) = deleted_handle(); // Mark the handle as deleted, allocate will reuse it 114 } 115} 116 117 118void JNIHandles::destroy_weak_global(jobject handle) { 119 if (handle != NULL) { 120 assert(!CheckJNICalls || is_weak_global_handle(handle), "Invalid delete of weak global JNI handle"); 121 *((oop*)handle) = deleted_handle(); // Mark the handle as deleted, allocate will reuse it 122 } 123} 124 125void JNIHandles::destroy_jmethod_id(jmethodID mid) { 126 destroy_weak_global((jobject)mid); 127} 128 129 130void JNIHandles::oops_do(OopClosure* f) { 131 f->do_oop(&_deleted_handle); 132 _global_handles->oops_do(f); 133} 134 135 136void JNIHandles::weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f) { 137 _weak_global_handles->weak_oops_do(is_alive, f); 138} 139 140 141void JNIHandles::initialize() { 142 _global_handles = JNIHandleBlock::allocate_block(); 143 _weak_global_handles = JNIHandleBlock::allocate_block(); 144 EXCEPTION_MARK; 145 // We will never reach the CATCH below since Exceptions::_throw will cause 146 // the VM to exit if an exception is thrown during initialization 147 klassOop k = SystemDictionary::object_klass(); 148 _deleted_handle = instanceKlass::cast(k)->allocate_permanent_instance(CATCH); 149} 150 151 152bool JNIHandles::is_local_handle(Thread* thread, jobject handle) { 153 JNIHandleBlock* block = thread->active_handles(); 154 155 // Look back past possible native calls to jni_PushLocalFrame. 156 while (block != NULL) { 157 if (block->chain_contains(handle)) { 158 return true; 159 } 160 block = block->pop_frame_link(); 161 } 162 return false; 163} 164 165 166// Determine if the handle is somewhere in the current thread's stack. 167// We easily can't isolate any particular stack frame the handle might 168// come from, so we'll check the whole stack. 169 170bool JNIHandles::is_frame_handle(JavaThread* thr, jobject obj) { 171 // If there is no java frame, then this must be top level code, such 172 // as the java command executable, in which case, this type of handle 173 // is not permitted. 174 return (thr->has_last_Java_frame() && 175 (void*)obj < (void*)thr->stack_base() && 176 (void*)obj >= (void*)thr->last_Java_sp()); 177} 178 179 180bool JNIHandles::is_global_handle(jobject handle) { 181 return _global_handles->chain_contains(handle); 182} 183 184 185bool JNIHandles::is_weak_global_handle(jobject handle) { 186 return _weak_global_handles->chain_contains(handle); 187} 188 189long JNIHandles::global_handle_memory_usage() { 190 return _global_handles->memory_usage(); 191} 192 193long JNIHandles::weak_global_handle_memory_usage() { 194 return _weak_global_handles->memory_usage(); 195} 196 197 198class AlwaysAliveClosure: public BoolObjectClosure { 199public: 200 bool do_object_b(oop obj) { return true; } 201 void do_object(oop obj) { assert(false, "Don't call"); } 202}; 203 204class CountHandleClosure: public OopClosure { 205private: 206 int _count; 207public: 208 CountHandleClosure(): _count(0) {} 209 virtual void do_oop(oop* unused) { 210 _count++; 211 } 212 virtual void do_oop(narrowOop* unused) { ShouldNotReachHere(); } 213 int count() { return _count; } 214}; 215 216// We assume this is called at a safepoint: no lock is needed. 217void JNIHandles::print_on(outputStream* st) { 218 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint"); 219 assert(_global_handles != NULL && _weak_global_handles != NULL, 220 "JNIHandles not initialized"); 221 222 CountHandleClosure global_handle_count; 223 AlwaysAliveClosure always_alive; 224 oops_do(&global_handle_count); 225 weak_oops_do(&always_alive, &global_handle_count); 226 227 st->print_cr("JNI global references: %d", global_handle_count.count()); 228 st->cr(); 229 st->flush(); 230} 231 232class VerifyHandleClosure: public OopClosure { 233public: 234 virtual void do_oop(oop* root) { 235 (*root)->verify(); 236 } 237 virtual void do_oop(narrowOop* root) { ShouldNotReachHere(); } 238}; 239 240void JNIHandles::verify() { 241 VerifyHandleClosure verify_handle; 242 AlwaysAliveClosure always_alive; 243 244 oops_do(&verify_handle); 245 weak_oops_do(&always_alive, &verify_handle); 246} 247 248 249 250void jni_handles_init() { 251 JNIHandles::initialize(); 252} 253 254 255int JNIHandleBlock::_blocks_allocated = 0; 256JNIHandleBlock* JNIHandleBlock::_block_free_list = NULL; 257#ifndef PRODUCT 258JNIHandleBlock* JNIHandleBlock::_block_list = NULL; 259#endif 260 261 262void JNIHandleBlock::zap() { 263 // Zap block values 264 _top = 0; 265 for (int index = 0; index < block_size_in_oops; index++) { 266 _handles[index] = badJNIHandle; 267 } 268} 269 270JNIHandleBlock* JNIHandleBlock::allocate_block(Thread* thread) { 271 assert(thread == NULL || thread == Thread::current(), "sanity check"); 272 JNIHandleBlock* block; 273 // Check the thread-local free list for a block so we don't 274 // have to acquire a mutex. 275 if (thread != NULL && thread->free_handle_block() != NULL) { 276 block = thread->free_handle_block(); 277 thread->set_free_handle_block(block->_next); 278 } 279 else { 280 // locking with safepoint checking introduces a potential deadlock: 281 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock 282 // - another would hold Threads_lock (jni_AttachCurrentThread) and then 283 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block) 284 MutexLockerEx ml(JNIHandleBlockFreeList_lock, 285 Mutex::_no_safepoint_check_flag); 286 if (_block_free_list == NULL) { 287 // Allocate new block 288 block = new JNIHandleBlock(); 289 _blocks_allocated++; 290 if (TraceJNIHandleAllocation) { 291 tty->print_cr("JNIHandleBlock " INTPTR_FORMAT " allocated (%d total blocks)", 292 block, _blocks_allocated); 293 } 294 if (ZapJNIHandleArea) block->zap(); 295 #ifndef PRODUCT 296 // Link new block to list of all allocated blocks 297 block->_block_list_link = _block_list; 298 _block_list = block; 299 #endif 300 } else { 301 // Get block from free list 302 block = _block_free_list; 303 _block_free_list = _block_free_list->_next; 304 } 305 } 306 block->_top = 0; 307 block->_next = NULL; 308 block->_pop_frame_link = NULL; 309 // _last, _free_list & _allocate_before_rebuild initialized in allocate_handle 310 debug_only(block->_last = NULL); 311 debug_only(block->_free_list = NULL); 312 debug_only(block->_allocate_before_rebuild = -1); 313 return block; 314} 315 316 317void JNIHandleBlock::release_block(JNIHandleBlock* block, Thread* thread) { 318 assert(thread == NULL || thread == Thread::current(), "sanity check"); 319 JNIHandleBlock* pop_frame_link = block->pop_frame_link(); 320 // Put returned block at the beginning of the thread-local free list. 321 // Note that if thread == NULL, we use it as an implicit argument that 322 // we _don't_ want the block to be kept on the free_handle_block. 323 // See for instance JavaThread::exit(). 324 if (thread != NULL ) { 325 if (ZapJNIHandleArea) block->zap(); 326 JNIHandleBlock* freelist = thread->free_handle_block(); 327 block->_pop_frame_link = NULL; 328 thread->set_free_handle_block(block); 329 330 // Add original freelist to end of chain 331 if ( freelist != NULL ) { 332 while ( block->_next != NULL ) block = block->_next; 333 block->_next = freelist; 334 } 335 block = NULL; 336 } 337 if (block != NULL) { 338 // Return blocks to free list 339 // locking with safepoint checking introduces a potential deadlock: 340 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock 341 // - another would hold Threads_lock (jni_AttachCurrentThread) and then 342 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block) 343 MutexLockerEx ml(JNIHandleBlockFreeList_lock, 344 Mutex::_no_safepoint_check_flag); 345 while (block != NULL) { 346 if (ZapJNIHandleArea) block->zap(); 347 JNIHandleBlock* next = block->_next; 348 block->_next = _block_free_list; 349 _block_free_list = block; 350 block = next; 351 } 352 } 353 if (pop_frame_link != NULL) { 354 // As a sanity check we release blocks pointed to by the pop_frame_link. 355 // This should never happen (only if PopLocalFrame is not called the 356 // correct number of times). 357 release_block(pop_frame_link, thread); 358 } 359} 360 361 362void JNIHandleBlock::oops_do(OopClosure* f) { 363 JNIHandleBlock* current_chain = this; 364 // Iterate over chain of blocks, followed by chains linked through the 365 // pop frame links. 366 while (current_chain != NULL) { 367 for (JNIHandleBlock* current = current_chain; current != NULL; 368 current = current->_next) { 369 assert(current == current_chain || current->pop_frame_link() == NULL, 370 "only blocks first in chain should have pop frame link set"); 371 for (int index = 0; index < current->_top; index++) { 372 oop* root = &(current->_handles)[index]; 373 oop value = *root; 374 // traverse heap pointers only, not deleted handles or free list 375 // pointers 376 if (value != NULL && Universe::heap()->is_in_reserved(value)) { 377 f->do_oop(root); 378 } 379 } 380 // the next handle block is valid only if current block is full 381 if (current->_top < block_size_in_oops) { 382 break; 383 } 384 } 385 current_chain = current_chain->pop_frame_link(); 386 } 387} 388 389 390void JNIHandleBlock::weak_oops_do(BoolObjectClosure* is_alive, 391 OopClosure* f) { 392 for (JNIHandleBlock* current = this; current != NULL; current = current->_next) { 393 assert(current->pop_frame_link() == NULL, 394 "blocks holding weak global JNI handles should not have pop frame link set"); 395 for (int index = 0; index < current->_top; index++) { 396 oop* root = &(current->_handles)[index]; 397 oop value = *root; 398 // traverse heap pointers only, not deleted handles or free list pointers 399 if (value != NULL && Universe::heap()->is_in_reserved(value)) { 400 if (is_alive->do_object_b(value)) { 401 // The weakly referenced object is alive, update pointer 402 f->do_oop(root); 403 } else { 404 // The weakly referenced object is not alive, clear the reference by storing NULL 405 if (TraceReferenceGC) { 406 tty->print_cr("Clearing JNI weak reference (" INTPTR_FORMAT ")", root); 407 } 408 *root = NULL; 409 } 410 } 411 } 412 // the next handle block is valid only if current block is full 413 if (current->_top < block_size_in_oops) { 414 break; 415 } 416 } 417} 418 419 420jobject JNIHandleBlock::allocate_handle(oop obj) { 421 assert(Universe::heap()->is_in_reserved(obj), "sanity check"); 422 if (_top == 0) { 423 // This is the first allocation or the initial block got zapped when 424 // entering a native function. If we have any following blocks they are 425 // not valid anymore. 426 for (JNIHandleBlock* current = _next; current != NULL; 427 current = current->_next) { 428 assert(current->_last == NULL, "only first block should have _last set"); 429 assert(current->_free_list == NULL, 430 "only first block should have _free_list set"); 431 current->_top = 0; 432 if (ZapJNIHandleArea) current->zap(); 433 } 434 // Clear initial block 435 _free_list = NULL; 436 _allocate_before_rebuild = 0; 437 _last = this; 438 if (ZapJNIHandleArea) zap(); 439 } 440 441 // Try last block 442 if (_last->_top < block_size_in_oops) { 443 oop* handle = &(_last->_handles)[_last->_top++]; 444 *handle = obj; 445 return (jobject) handle; 446 } 447 448 // Try free list 449 if (_free_list != NULL) { 450 oop* handle = _free_list; 451 _free_list = (oop*) *_free_list; 452 *handle = obj; 453 return (jobject) handle; 454 } 455 // Check if unused block follow last 456 if (_last->_next != NULL) { 457 // update last and retry 458 _last = _last->_next; 459 return allocate_handle(obj); 460 } 461 462 // No space available, we have to rebuild free list or expand 463 if (_allocate_before_rebuild == 0) { 464 rebuild_free_list(); // updates _allocate_before_rebuild counter 465 } else { 466 // Append new block 467 Thread* thread = Thread::current(); 468 Handle obj_handle(thread, obj); 469 // This can block, so we need to preserve obj accross call. 470 _last->_next = JNIHandleBlock::allocate_block(thread); 471 _last = _last->_next; 472 _allocate_before_rebuild--; 473 obj = obj_handle(); 474 } 475 return allocate_handle(obj); // retry 476} 477 478 479void JNIHandleBlock::rebuild_free_list() { 480 assert(_allocate_before_rebuild == 0 && _free_list == NULL, "just checking"); 481 int free = 0; 482 int blocks = 0; 483 for (JNIHandleBlock* current = this; current != NULL; current = current->_next) { 484 for (int index = 0; index < current->_top; index++) { 485 oop* handle = &(current->_handles)[index]; 486 if (*handle == JNIHandles::deleted_handle()) { 487 // this handle was cleared out by a delete call, reuse it 488 *handle = (oop) _free_list; 489 _free_list = handle; 490 free++; 491 } 492 } 493 // we should not rebuild free list if there are unused handles at the end 494 assert(current->_top == block_size_in_oops, "just checking"); 495 blocks++; 496 } 497 // Heuristic: if more than half of the handles are free we rebuild next time 498 // as well, otherwise we append a corresponding number of new blocks before 499 // attempting a free list rebuild again. 500 int total = blocks * block_size_in_oops; 501 int extra = total - 2*free; 502 if (extra > 0) { 503 // Not as many free handles as we would like - compute number of new blocks to append 504 _allocate_before_rebuild = (extra + block_size_in_oops - 1) / block_size_in_oops; 505 } 506 if (TraceJNIHandleAllocation) { 507 tty->print_cr("Rebuild free list JNIHandleBlock " INTPTR_FORMAT " blocks=%d used=%d free=%d add=%d", 508 this, blocks, total-free, free, _allocate_before_rebuild); 509 } 510} 511 512 513bool JNIHandleBlock::contains(jobject handle) const { 514 return ((jobject)&_handles[0] <= handle && handle<(jobject)&_handles[_top]); 515} 516 517 518bool JNIHandleBlock::chain_contains(jobject handle) const { 519 for (JNIHandleBlock* current = (JNIHandleBlock*) this; current != NULL; current = current->_next) { 520 if (current->contains(handle)) { 521 return true; 522 } 523 } 524 return false; 525} 526 527 528int JNIHandleBlock::length() const { 529 int result = 1; 530 for (JNIHandleBlock* current = _next; current != NULL; current = current->_next) { 531 result++; 532 } 533 return result; 534} 535 536// This method is not thread-safe, i.e., must be called whule holding a lock on the 537// structure. 538long JNIHandleBlock::memory_usage() const { 539 return length() * sizeof(JNIHandleBlock); 540} 541 542 543#ifndef PRODUCT 544 545bool JNIHandleBlock::any_contains(jobject handle) { 546 for (JNIHandleBlock* current = _block_list; current != NULL; current = current->_block_list_link) { 547 if (current->contains(handle)) { 548 return true; 549 } 550 } 551 return false; 552} 553 554void JNIHandleBlock::print_statistics() { 555 int used_blocks = 0; 556 int free_blocks = 0; 557 int used_handles = 0; 558 int free_handles = 0; 559 JNIHandleBlock* block = _block_list; 560 while (block != NULL) { 561 if (block->_top > 0) { 562 used_blocks++; 563 } else { 564 free_blocks++; 565 } 566 used_handles += block->_top; 567 free_handles += (block_size_in_oops - block->_top); 568 block = block->_block_list_link; 569 } 570 tty->print_cr("JNIHandleBlocks statistics"); 571 tty->print_cr("- blocks allocated: %d", used_blocks + free_blocks); 572 tty->print_cr("- blocks in use: %d", used_blocks); 573 tty->print_cr("- blocks free: %d", free_blocks); 574 tty->print_cr("- handles in use: %d", used_handles); 575 tty->print_cr("- handles free: %d", free_handles); 576} 577 578#endif 579