jniHandles.cpp revision 0:a61af66fc99e
1/* 2 * Copyright 1998-2007 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 void do_oop(oop* unused) { 210 _count++; 211 } 212 int count() { return _count; } 213}; 214 215// We assume this is called at a safepoint: no lock is needed. 216void JNIHandles::print_on(outputStream* st) { 217 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint"); 218 assert(_global_handles != NULL && _weak_global_handles != NULL, 219 "JNIHandles not initialized"); 220 221 CountHandleClosure global_handle_count; 222 AlwaysAliveClosure always_alive; 223 oops_do(&global_handle_count); 224 weak_oops_do(&always_alive, &global_handle_count); 225 226 st->print_cr("JNI global references: %d", global_handle_count.count()); 227 st->cr(); 228 st->flush(); 229} 230 231class VerifyHandleClosure: public OopClosure { 232public: 233 void do_oop(oop* root) { 234 (*root)->verify(); 235 } 236}; 237 238void JNIHandles::verify() { 239 VerifyHandleClosure verify_handle; 240 AlwaysAliveClosure always_alive; 241 242 oops_do(&verify_handle); 243 weak_oops_do(&always_alive, &verify_handle); 244} 245 246 247 248void jni_handles_init() { 249 JNIHandles::initialize(); 250} 251 252 253int JNIHandleBlock::_blocks_allocated = 0; 254JNIHandleBlock* JNIHandleBlock::_block_free_list = NULL; 255#ifndef PRODUCT 256JNIHandleBlock* JNIHandleBlock::_block_list = NULL; 257#endif 258 259 260void JNIHandleBlock::zap() { 261 // Zap block values 262 _top = 0; 263 for (int index = 0; index < block_size_in_oops; index++) { 264 _handles[index] = badJNIHandle; 265 } 266} 267 268JNIHandleBlock* JNIHandleBlock::allocate_block(Thread* thread) { 269 assert(thread == NULL || thread == Thread::current(), "sanity check"); 270 JNIHandleBlock* block; 271 // Check the thread-local free list for a block so we don't 272 // have to acquire a mutex. 273 if (thread != NULL && thread->free_handle_block() != NULL) { 274 block = thread->free_handle_block(); 275 thread->set_free_handle_block(block->_next); 276 } 277 else { 278 // locking with safepoint checking introduces a potential deadlock: 279 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock 280 // - another would hold Threads_lock (jni_AttachCurrentThread) and then 281 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block) 282 MutexLockerEx ml(JNIHandleBlockFreeList_lock, 283 Mutex::_no_safepoint_check_flag); 284 if (_block_free_list == NULL) { 285 // Allocate new block 286 block = new JNIHandleBlock(); 287 _blocks_allocated++; 288 if (TraceJNIHandleAllocation) { 289 tty->print_cr("JNIHandleBlock " INTPTR_FORMAT " allocated (%d total blocks)", 290 block, _blocks_allocated); 291 } 292 if (ZapJNIHandleArea) block->zap(); 293 #ifndef PRODUCT 294 // Link new block to list of all allocated blocks 295 block->_block_list_link = _block_list; 296 _block_list = block; 297 #endif 298 } else { 299 // Get block from free list 300 block = _block_free_list; 301 _block_free_list = _block_free_list->_next; 302 } 303 } 304 block->_top = 0; 305 block->_next = NULL; 306 block->_pop_frame_link = NULL; 307 // _last, _free_list & _allocate_before_rebuild initialized in allocate_handle 308 debug_only(block->_last = NULL); 309 debug_only(block->_free_list = NULL); 310 debug_only(block->_allocate_before_rebuild = -1); 311 return block; 312} 313 314 315void JNIHandleBlock::release_block(JNIHandleBlock* block, Thread* thread) { 316 assert(thread == NULL || thread == Thread::current(), "sanity check"); 317 JNIHandleBlock* pop_frame_link = block->pop_frame_link(); 318 // Put returned block at the beginning of the thread-local free list. 319 // Note that if thread == NULL, we use it as an implicit argument that 320 // we _don't_ want the block to be kept on the free_handle_block. 321 // See for instance JavaThread::exit(). 322 if (thread != NULL ) { 323 if (ZapJNIHandleArea) block->zap(); 324 JNIHandleBlock* freelist = thread->free_handle_block(); 325 block->_pop_frame_link = NULL; 326 thread->set_free_handle_block(block); 327 328 // Add original freelist to end of chain 329 if ( freelist != NULL ) { 330 while ( block->_next != NULL ) block = block->_next; 331 block->_next = freelist; 332 } 333 block = NULL; 334 } 335 if (block != NULL) { 336 // Return blocks to free list 337 // locking with safepoint checking introduces a potential deadlock: 338 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock 339 // - another would hold Threads_lock (jni_AttachCurrentThread) and then 340 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block) 341 MutexLockerEx ml(JNIHandleBlockFreeList_lock, 342 Mutex::_no_safepoint_check_flag); 343 while (block != NULL) { 344 if (ZapJNIHandleArea) block->zap(); 345 JNIHandleBlock* next = block->_next; 346 block->_next = _block_free_list; 347 _block_free_list = block; 348 block = next; 349 } 350 } 351 if (pop_frame_link != NULL) { 352 // As a sanity check we release blocks pointed to by the pop_frame_link. 353 // This should never happen (only if PopLocalFrame is not called the 354 // correct number of times). 355 release_block(pop_frame_link, thread); 356 } 357} 358 359 360void JNIHandleBlock::oops_do(OopClosure* f) { 361 JNIHandleBlock* current_chain = this; 362 // Iterate over chain of blocks, followed by chains linked through the 363 // pop frame links. 364 while (current_chain != NULL) { 365 for (JNIHandleBlock* current = current_chain; current != NULL; 366 current = current->_next) { 367 assert(current == current_chain || current->pop_frame_link() == NULL, 368 "only blocks first in chain should have pop frame link set"); 369 for (int index = 0; index < current->_top; index++) { 370 oop* root = &(current->_handles)[index]; 371 oop value = *root; 372 // traverse heap pointers only, not deleted handles or free list 373 // pointers 374 if (value != NULL && Universe::heap()->is_in_reserved(value)) { 375 f->do_oop(root); 376 } 377 } 378 // the next handle block is valid only if current block is full 379 if (current->_top < block_size_in_oops) { 380 break; 381 } 382 } 383 current_chain = current_chain->pop_frame_link(); 384 } 385} 386 387 388void JNIHandleBlock::weak_oops_do(BoolObjectClosure* is_alive, 389 OopClosure* f) { 390 for (JNIHandleBlock* current = this; current != NULL; current = current->_next) { 391 assert(current->pop_frame_link() == NULL, 392 "blocks holding weak global JNI handles should not have pop frame link set"); 393 for (int index = 0; index < current->_top; index++) { 394 oop* root = &(current->_handles)[index]; 395 oop value = *root; 396 // traverse heap pointers only, not deleted handles or free list pointers 397 if (value != NULL && Universe::heap()->is_in_reserved(value)) { 398 if (is_alive->do_object_b(value)) { 399 // The weakly referenced object is alive, update pointer 400 f->do_oop(root); 401 } else { 402 // The weakly referenced object is not alive, clear the reference by storing NULL 403 if (TraceReferenceGC) { 404 tty->print_cr("Clearing JNI weak reference (" INTPTR_FORMAT ")", root); 405 } 406 *root = NULL; 407 } 408 } 409 } 410 // the next handle block is valid only if current block is full 411 if (current->_top < block_size_in_oops) { 412 break; 413 } 414 } 415} 416 417 418jobject JNIHandleBlock::allocate_handle(oop obj) { 419 assert(Universe::heap()->is_in_reserved(obj), "sanity check"); 420 if (_top == 0) { 421 // This is the first allocation or the initial block got zapped when 422 // entering a native function. If we have any following blocks they are 423 // not valid anymore. 424 for (JNIHandleBlock* current = _next; current != NULL; 425 current = current->_next) { 426 assert(current->_last == NULL, "only first block should have _last set"); 427 assert(current->_free_list == NULL, 428 "only first block should have _free_list set"); 429 current->_top = 0; 430 if (ZapJNIHandleArea) current->zap(); 431 } 432 // Clear initial block 433 _free_list = NULL; 434 _allocate_before_rebuild = 0; 435 _last = this; 436 if (ZapJNIHandleArea) zap(); 437 } 438 439 // Try last block 440 if (_last->_top < block_size_in_oops) { 441 oop* handle = &(_last->_handles)[_last->_top++]; 442 *handle = obj; 443 return (jobject) handle; 444 } 445 446 // Try free list 447 if (_free_list != NULL) { 448 oop* handle = _free_list; 449 _free_list = (oop*) *_free_list; 450 *handle = obj; 451 return (jobject) handle; 452 } 453 // Check if unused block follow last 454 if (_last->_next != NULL) { 455 // update last and retry 456 _last = _last->_next; 457 return allocate_handle(obj); 458 } 459 460 // No space available, we have to rebuild free list or expand 461 if (_allocate_before_rebuild == 0) { 462 rebuild_free_list(); // updates _allocate_before_rebuild counter 463 } else { 464 // Append new block 465 Thread* thread = Thread::current(); 466 Handle obj_handle(thread, obj); 467 // This can block, so we need to preserve obj accross call. 468 _last->_next = JNIHandleBlock::allocate_block(thread); 469 _last = _last->_next; 470 _allocate_before_rebuild--; 471 obj = obj_handle(); 472 } 473 return allocate_handle(obj); // retry 474} 475 476 477void JNIHandleBlock::rebuild_free_list() { 478 assert(_allocate_before_rebuild == 0 && _free_list == NULL, "just checking"); 479 int free = 0; 480 int blocks = 0; 481 for (JNIHandleBlock* current = this; current != NULL; current = current->_next) { 482 for (int index = 0; index < current->_top; index++) { 483 oop* handle = &(current->_handles)[index]; 484 if (*handle == JNIHandles::deleted_handle()) { 485 // this handle was cleared out by a delete call, reuse it 486 *handle = (oop) _free_list; 487 _free_list = handle; 488 free++; 489 } 490 } 491 // we should not rebuild free list if there are unused handles at the end 492 assert(current->_top == block_size_in_oops, "just checking"); 493 blocks++; 494 } 495 // Heuristic: if more than half of the handles are free we rebuild next time 496 // as well, otherwise we append a corresponding number of new blocks before 497 // attempting a free list rebuild again. 498 int total = blocks * block_size_in_oops; 499 int extra = total - 2*free; 500 if (extra > 0) { 501 // Not as many free handles as we would like - compute number of new blocks to append 502 _allocate_before_rebuild = (extra + block_size_in_oops - 1) / block_size_in_oops; 503 } 504 if (TraceJNIHandleAllocation) { 505 tty->print_cr("Rebuild free list JNIHandleBlock " INTPTR_FORMAT " blocks=%d used=%d free=%d add=%d", 506 this, blocks, total-free, free, _allocate_before_rebuild); 507 } 508} 509 510 511bool JNIHandleBlock::contains(jobject handle) const { 512 return ((jobject)&_handles[0] <= handle && handle<(jobject)&_handles[_top]); 513} 514 515 516bool JNIHandleBlock::chain_contains(jobject handle) const { 517 for (JNIHandleBlock* current = (JNIHandleBlock*) this; current != NULL; current = current->_next) { 518 if (current->contains(handle)) { 519 return true; 520 } 521 } 522 return false; 523} 524 525 526int JNIHandleBlock::length() const { 527 int result = 1; 528 for (JNIHandleBlock* current = _next; current != NULL; current = current->_next) { 529 result++; 530 } 531 return result; 532} 533 534// This method is not thread-safe, i.e., must be called whule holding a lock on the 535// structure. 536long JNIHandleBlock::memory_usage() const { 537 return length() * sizeof(JNIHandleBlock); 538} 539 540 541#ifndef PRODUCT 542 543bool JNIHandleBlock::any_contains(jobject handle) { 544 for (JNIHandleBlock* current = _block_list; current != NULL; current = current->_block_list_link) { 545 if (current->contains(handle)) { 546 return true; 547 } 548 } 549 return false; 550} 551 552void JNIHandleBlock::print_statistics() { 553 int used_blocks = 0; 554 int free_blocks = 0; 555 int used_handles = 0; 556 int free_handles = 0; 557 JNIHandleBlock* block = _block_list; 558 while (block != NULL) { 559 if (block->_top > 0) { 560 used_blocks++; 561 } else { 562 free_blocks++; 563 } 564 used_handles += block->_top; 565 free_handles += (block_size_in_oops - block->_top); 566 block = block->_block_list_link; 567 } 568 tty->print_cr("JNIHandleBlocks statistics"); 569 tty->print_cr("- blocks allocated: %d", used_blocks + free_blocks); 570 tty->print_cr("- blocks in use: %d", used_blocks); 571 tty->print_cr("- blocks free: %d", free_blocks); 572 tty->print_cr("- handles in use: %d", used_handles); 573 tty->print_cr("- handles free: %d", free_handles); 574} 575 576#endif 577