1 /* 2 * Copyright (c) 2017, 2018, 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 "logging/logStream.hpp" 27 #include "memory/allocation.inline.hpp" 28 #include "runtime/jniHandles.inline.hpp" 29 #include "runtime/thread.inline.hpp" 30 #include "runtime/threadSMR.inline.hpp" 31 #include "runtime/vm_operations.hpp" 32 #include "services/threadService.hpp" 33 #include "utilities/copy.hpp" 34 #include "utilities/globalDefinitions.hpp" 35 #include "utilities/ostream.hpp" 36 #include "utilities/resourceHash.hpp" 37 #include "utilities/vmError.hpp" 38 39 // The '_cnt', '_max' and '_times" fields are enabled via 40 // -XX:+EnableThreadSMRStatistics: 41 42 // # of parallel threads in _delete_lock->wait(). 43 // Impl note: Hard to imagine > 64K waiting threads so this could be 16-bit, 44 // but there is no nice 16-bit _FORMAT support. 45 uint ThreadsSMRSupport::_delete_lock_wait_cnt = 0; 46 47 // Max # of parallel threads in _delete_lock->wait(). 48 // Impl note: See _delete_lock_wait_cnt note. 49 uint ThreadsSMRSupport::_delete_lock_wait_max = 0; 50 51 // Flag to indicate when an _delete_lock->notify() is needed. 52 // Impl note: See _delete_lock_wait_cnt note. 53 volatile uint ThreadsSMRSupport::_delete_notify = 0; 54 55 // # of threads deleted over VM lifetime. 56 // Impl note: Atomically incremented over VM lifetime so use unsigned for more 57 // range. Unsigned 64-bit would be more future proof, but 64-bit atomic inc 58 // isn't available everywhere (or is it?). 59 volatile uint ThreadsSMRSupport::_deleted_thread_cnt = 0; 60 61 // Max time in millis to delete a thread. 62 // Impl note: 16-bit might be too small on an overloaded machine. Use 63 // unsigned since this is a time value. Set via Atomic::cmpxchg() in a 64 // loop for correctness. 65 volatile uint ThreadsSMRSupport::_deleted_thread_time_max = 0; 66 67 // Cumulative time in millis to delete threads. 68 // Impl note: Atomically added to over VM lifetime so use unsigned for more 69 // range. Unsigned 64-bit would be more future proof, but 64-bit atomic inc 70 // isn't available everywhere (or is it?). 71 volatile uint ThreadsSMRSupport::_deleted_thread_times = 0; 72 73 // The bootstrap list is empty and cannot be freed. 74 ThreadsList ThreadsSMRSupport::_bootstrap_list = ThreadsList(0); 75 76 // This is the VM's current "threads list" and it contains all of 77 // the JavaThreads the VM considers to be alive at this moment in 78 // time. The other ThreadsList objects in the VM contain past 79 // snapshots of the "threads list". _java_thread_list is initially 80 // set to _bootstrap_list so that we can detect when we have a very 81 // early use of a ThreadsListHandle. 82 ThreadsList* volatile ThreadsSMRSupport::_java_thread_list = &_bootstrap_list; 83 84 // # of ThreadsLists allocated over VM lifetime. 85 // Impl note: We allocate a new ThreadsList for every thread create and 86 // every thread delete so we need a bigger type than the 87 // _deleted_thread_cnt field. 88 uint64_t ThreadsSMRSupport::_java_thread_list_alloc_cnt = 1; 89 90 // # of ThreadsLists freed over VM lifetime. 91 // Impl note: See _java_thread_list_alloc_cnt note. 92 uint64_t ThreadsSMRSupport::_java_thread_list_free_cnt = 0; 93 94 // Max size ThreadsList allocated. 95 // Impl note: Max # of threads alive at one time should fit in unsigned 32-bit. 96 uint ThreadsSMRSupport::_java_thread_list_max = 0; 97 98 // Max # of nested ThreadsLists for a thread. 99 // Impl note: Hard to imagine > 64K nested ThreadsLists so this could be 100 // 16-bit, but there is no nice 16-bit _FORMAT support. 101 uint ThreadsSMRSupport::_nested_thread_list_max = 0; 102 103 // # of ThreadsListHandles deleted over VM lifetime. 104 // Impl note: Atomically incremented over VM lifetime so use unsigned for 105 // more range. There will be fewer ThreadsListHandles than threads so 106 // unsigned 32-bit should be fine. 107 volatile uint ThreadsSMRSupport::_tlh_cnt = 0; 108 109 // Max time in millis to delete a ThreadsListHandle. 110 // Impl note: 16-bit might be too small on an overloaded machine. Use 111 // unsigned since this is a time value. Set via Atomic::cmpxchg() in a 112 // loop for correctness. 113 volatile uint ThreadsSMRSupport::_tlh_time_max = 0; 114 115 // Cumulative time in millis to delete ThreadsListHandles. 116 // Impl note: Atomically added to over VM lifetime so use unsigned for more 117 // range. Unsigned 64-bit would be more future proof, but 64-bit atomic inc 118 // isn't available everywhere (or is it?). 119 volatile uint ThreadsSMRSupport::_tlh_times = 0; 120 121 ThreadsList* ThreadsSMRSupport::_to_delete_list = NULL; 122 123 // # of parallel ThreadsLists on the to-delete list. 124 // Impl note: Hard to imagine > 64K ThreadsLists needing to be deleted so 125 // this could be 16-bit, but there is no nice 16-bit _FORMAT support. 126 uint ThreadsSMRSupport::_to_delete_list_cnt = 0; 127 128 // Max # of parallel ThreadsLists on the to-delete list. 129 // Impl note: See _to_delete_list_cnt note. 130 uint ThreadsSMRSupport::_to_delete_list_max = 0; 131 132 133 // 'inline' functions first so the definitions are before first use: 134 135 inline void ThreadsSMRSupport::add_deleted_thread_times(uint add_value) { 136 Atomic::add(add_value, &_deleted_thread_times); 137 } 138 139 inline void ThreadsSMRSupport::inc_deleted_thread_cnt() { 140 Atomic::inc(&_deleted_thread_cnt); 141 } 142 143 inline void ThreadsSMRSupport::inc_java_thread_list_alloc_cnt() { 144 _java_thread_list_alloc_cnt++; 145 } 146 147 inline bool ThreadsSMRSupport::is_bootstrap_list(ThreadsList* list) { 148 return list == &_bootstrap_list; 149 } 150 151 inline void ThreadsSMRSupport::update_deleted_thread_time_max(uint new_value) { 152 while (true) { 153 uint cur_value = _deleted_thread_time_max; 154 if (new_value <= cur_value) { 155 // No need to update max value so we're done. 156 break; 157 } 158 if (Atomic::cmpxchg(new_value, &_deleted_thread_time_max, cur_value) == cur_value) { 159 // Updated max value so we're done. Otherwise try it all again. 160 break; 161 } 162 } 163 } 164 165 inline void ThreadsSMRSupport::update_java_thread_list_max(uint new_value) { 166 if (new_value > _java_thread_list_max) { 167 _java_thread_list_max = new_value; 168 } 169 } 170 171 inline ThreadsList* ThreadsSMRSupport::xchg_java_thread_list(ThreadsList* new_list) { 172 return (ThreadsList*)Atomic::xchg(new_list, &_java_thread_list); 173 } 174 175 // Hash table of pointers found by a scan. Used for collecting hazard 176 // pointers (ThreadsList references). Also used for collecting JavaThreads 177 // that are indirectly referenced by hazard ptrs. An instance of this 178 // class only contains one type of pointer. 179 // 180 class ThreadScanHashtable : public CHeapObj<mtThread> { 181 private: 182 static bool ptr_equals(void * const& s1, void * const& s2) { 183 return s1 == s2; 184 } 185 186 static unsigned int ptr_hash(void * const& s1) { 187 // 2654435761 = 2^32 * Phi (golden ratio) 188 return (unsigned int)(((uint32_t)(uintptr_t)s1) * 2654435761u); 189 } 190 191 int _table_size; 192 // ResourceHashtable SIZE is specified at compile time so our 193 // dynamic _table_size is unused for now; 1031 is the first prime 194 // after 1024. 195 typedef ResourceHashtable<void *, int, &ThreadScanHashtable::ptr_hash, 196 &ThreadScanHashtable::ptr_equals, 1031, 197 ResourceObj::C_HEAP, mtThread> PtrTable; 198 PtrTable * _ptrs; 199 200 public: 201 // ResourceHashtable is passed to various functions and populated in 202 // different places so we allocate it using C_HEAP to make it immune 203 // from any ResourceMarks that happen to be in the code paths. 204 ThreadScanHashtable(int table_size) : _table_size(table_size), _ptrs(new (ResourceObj::C_HEAP, mtThread) PtrTable()) {} 205 206 ~ThreadScanHashtable() { delete _ptrs; } 207 208 bool has_entry(void *pointer) { 209 int *val_ptr = _ptrs->get(pointer); 210 return val_ptr != NULL && *val_ptr == 1; 211 } 212 213 void add_entry(void *pointer) { 214 _ptrs->put(pointer, 1); 215 } 216 }; 217 218 // Closure to gather JavaThreads indirectly referenced by hazard ptrs 219 // (ThreadsList references) into a hash table. This closure handles part 2 220 // of the dance - adding all the JavaThreads referenced by the hazard 221 // pointer (ThreadsList reference) to the hash table. 222 // 223 class AddThreadHazardPointerThreadClosure : public ThreadClosure { 224 private: 225 ThreadScanHashtable *_table; 226 227 public: 228 AddThreadHazardPointerThreadClosure(ThreadScanHashtable *table) : _table(table) {} 229 230 virtual void do_thread(Thread *thread) { 231 if (!_table->has_entry((void*)thread)) { 232 // The same JavaThread might be on more than one ThreadsList or 233 // more than one thread might be using the same ThreadsList. In 234 // either case, we only need a single entry for a JavaThread. 235 _table->add_entry((void*)thread); 236 } 237 } 238 }; 239 240 // Closure to gather JavaThreads indirectly referenced by hazard ptrs 241 // (ThreadsList references) into a hash table. This closure handles part 1 242 // of the dance - hazard ptr chain walking and dispatch to another 243 // closure. 244 // 245 class ScanHazardPtrGatherProtectedThreadsClosure : public ThreadClosure { 246 private: 247 ThreadScanHashtable *_table; 248 public: 249 ScanHazardPtrGatherProtectedThreadsClosure(ThreadScanHashtable *table) : _table(table) {} 250 251 virtual void do_thread(Thread *thread) { 252 assert_locked_or_safepoint(Threads_lock); 253 254 if (thread == NULL) return; 255 256 // This code races with ThreadsSMRSupport::acquire_stable_list() which 257 // is lock-free so we have to handle some special situations. 258 // 259 ThreadsList *current_list = NULL; 260 while (true) { 261 current_list = thread->get_threads_hazard_ptr(); 262 // No hazard ptr so nothing more to do. 263 if (current_list == NULL) { 264 return; 265 } 266 267 // If the hazard ptr is verified as stable (since it is not tagged), 268 // then it is safe to use. 269 if (!Thread::is_hazard_ptr_tagged(current_list)) break; 270 271 // The hazard ptr is tagged as not yet verified as being stable 272 // so we are racing with acquire_stable_list(). This exchange 273 // attempts to invalidate the hazard ptr. If we win the race, 274 // then we can ignore this unstable hazard ptr and the other 275 // thread will retry the attempt to publish a stable hazard ptr. 276 // If we lose the race, then we retry our attempt to look at the 277 // hazard ptr. 278 if (thread->cmpxchg_threads_hazard_ptr(NULL, current_list) == current_list) return; 279 } 280 281 // The current JavaThread has a hazard ptr (ThreadsList reference) 282 // which might be _java_thread_list or it might be an older 283 // ThreadsList that has been removed but not freed. In either case, 284 // the hazard ptr is protecting all the JavaThreads on that 285 // ThreadsList. 286 AddThreadHazardPointerThreadClosure add_cl(_table); 287 current_list->threads_do(&add_cl); 288 } 289 }; 290 291 // Closure to gather hazard ptrs (ThreadsList references) into a hash table. 292 // 293 class ScanHazardPtrGatherThreadsListClosure : public ThreadClosure { 294 private: 295 ThreadScanHashtable *_table; 296 public: 297 ScanHazardPtrGatherThreadsListClosure(ThreadScanHashtable *table) : _table(table) {} 298 299 virtual void do_thread(Thread* thread) { 300 assert_locked_or_safepoint(Threads_lock); 301 302 if (thread == NULL) return; 303 ThreadsList *threads = thread->get_threads_hazard_ptr(); 304 if (threads == NULL) { 305 return; 306 } 307 // In this closure we always ignore the tag that might mark this 308 // hazard ptr as not yet verified. If we happen to catch an 309 // unverified hazard ptr that is subsequently discarded (not 310 // published), then the only side effect is that we might keep a 311 // to-be-deleted ThreadsList alive a little longer. 312 threads = Thread::untag_hazard_ptr(threads); 313 if (!_table->has_entry((void*)threads)) { 314 _table->add_entry((void*)threads); 315 } 316 } 317 }; 318 319 // Closure to print JavaThreads that have a hazard ptr (ThreadsList 320 // reference) that contains an indirect reference to a specific JavaThread. 321 // 322 class ScanHazardPtrPrintMatchingThreadsClosure : public ThreadClosure { 323 private: 324 JavaThread *_thread; 325 public: 326 ScanHazardPtrPrintMatchingThreadsClosure(JavaThread *thread) : _thread(thread) {} 327 328 virtual void do_thread(Thread *thread) { 329 assert_locked_or_safepoint(Threads_lock); 330 331 if (thread == NULL) return; 332 ThreadsList *current_list = thread->get_threads_hazard_ptr(); 333 if (current_list == NULL) { 334 return; 335 } 336 // If the hazard ptr is unverified, then ignore it. 337 if (Thread::is_hazard_ptr_tagged(current_list)) return; 338 339 // The current JavaThread has a hazard ptr (ThreadsList reference) 340 // which might be _java_thread_list or it might be an older 341 // ThreadsList that has been removed but not freed. In either case, 342 // the hazard ptr is protecting all the JavaThreads on that 343 // ThreadsList, but we only care about matching a specific JavaThread. 344 JavaThreadIterator jti(current_list); 345 for (JavaThread *p = jti.first(); p != NULL; p = jti.next()) { 346 if (p == _thread) { 347 log_debug(thread, smr)("tid=" UINTX_FORMAT ": ThreadsSMRSupport::smr_delete: thread1=" INTPTR_FORMAT " has a hazard pointer for thread2=" INTPTR_FORMAT, os::current_thread_id(), p2i(thread), p2i(_thread)); 348 break; 349 } 350 } 351 } 352 }; 353 354 // Closure to determine if the specified JavaThread is found by 355 // threads_do(). 356 // 357 class VerifyHazardPtrThreadClosure : public ThreadClosure { 358 private: 359 bool _found; 360 Thread *_self; 361 362 public: 363 VerifyHazardPtrThreadClosure(Thread *self) : _found(false), _self(self) {} 364 365 bool found() const { return _found; } 366 367 virtual void do_thread(Thread *thread) { 368 if (thread == _self) { 369 _found = true; 370 } 371 } 372 }; 373 374 375 // Acquire a stable ThreadsList. 376 // 377 void SafeThreadsListPtr::acquire_stable_list() { 378 assert(_thread != NULL, "sanity check"); 379 _needs_release = true; 380 _previous = _thread->_threads_list_ptr; 381 _thread->_threads_list_ptr = this; 382 383 if (_thread->get_threads_hazard_ptr() == NULL) { 384 // The typical case is first. 385 acquire_stable_list_fast_path(); 386 return; 387 } 388 389 // The nested case is rare. 390 acquire_stable_list_nested_path(); 391 } 392 393 // Fast path way to acquire a stable ThreadsList. 394 // 395 void SafeThreadsListPtr::acquire_stable_list_fast_path() { 396 assert(_thread != NULL, "sanity check"); 397 assert(_thread->get_threads_hazard_ptr() == NULL, "sanity check"); 398 399 ThreadsList* threads; 400 401 // Stable recording of a hazard ptr for SMR. This code does not use 402 // locks so its use of the _smr_java_thread_list & _threads_hazard_ptr 403 // fields is racy relative to code that uses those fields with locks. 404 // OrderAccess and Atomic functions are used to deal with those races. 405 // 406 while (true) { 407 threads = ThreadsSMRSupport::get_java_thread_list(); 408 409 // Publish a tagged hazard ptr to denote that the hazard ptr is not 410 // yet verified as being stable. Due to the fence after the hazard 411 // ptr write, it will be sequentially consistent w.r.t. the 412 // sequentially consistent writes of the ThreadsList, even on 413 // non-multiple copy atomic machines where stores can be observed 414 // in different order from different observer threads. 415 ThreadsList* unverified_threads = Thread::tag_hazard_ptr(threads); 416 _thread->set_threads_hazard_ptr(unverified_threads); 417 418 // If _smr_java_thread_list has changed, we have lost a race with 419 // Threads::add() or Threads::remove() and have to try again. 420 if (ThreadsSMRSupport::get_java_thread_list() != threads) { 421 continue; 422 } 423 424 // We try to remove the tag which will verify the hazard ptr as 425 // being stable. This exchange can race with a scanning thread 426 // which might invalidate the tagged hazard ptr to keep it from 427 // being followed to access JavaThread ptrs. If we lose the race, 428 // we simply retry. If we win the race, then the stable hazard 429 // ptr is officially published. 430 if (_thread->cmpxchg_threads_hazard_ptr(threads, unverified_threads) == unverified_threads) { 431 break; 432 } 433 } 434 435 // A stable hazard ptr has been published letting other threads know 436 // that the ThreadsList and the JavaThreads reachable from this list 437 // are protected and hence they should not be deleted until everyone 438 // agrees it is safe to do so. 439 440 _list = threads; 441 442 verify_hazard_ptr_scanned(); 443 } 444 445 // Acquire a nested stable ThreadsList; this is rare so it uses 446 // reference counting. 447 // 448 void SafeThreadsListPtr::acquire_stable_list_nested_path() { 449 assert(_thread != NULL, "sanity check"); 450 assert(_thread->get_threads_hazard_ptr() != NULL, 451 "cannot have a NULL regular hazard ptr when acquiring a nested hazard ptr"); 452 453 // The thread already has a hazard ptr (ThreadsList ref) so we need 454 // to create a nested ThreadsListHandle with the current ThreadsList 455 // since it might be different than our current hazard ptr. To remedy 456 // the situation, the ThreadsList pointed to by the pre-existing 457 // stable hazard ptr is reference counted before the hazard ptr may 458 // be released and moved to a new ThreadsList. The old ThreadsList 459 // is remembered in the ThreadsListHandle. 460 461 ThreadsList* current_list = _previous->_list; 462 if (EnableThreadSMRStatistics) { 463 _thread->inc_nested_threads_hazard_ptr_cnt(); 464 } 465 current_list->inc_nested_handle_cnt(); 466 _previous->_has_ref_count = true; // promote SafeThreadsListPtr to be reference counted 467 _thread->_threads_hazard_ptr = NULL; // clear the hazard ptr so we can go through the fast path below 468 469 if (EnableThreadSMRStatistics && _thread->nested_threads_hazard_ptr_cnt() > ThreadsSMRSupport::_nested_thread_list_max) { 470 ThreadsSMRSupport::_nested_thread_list_max = _thread->nested_threads_hazard_ptr_cnt(); 471 } 472 473 acquire_stable_list_fast_path(); 474 475 verify_hazard_ptr_scanned(); 476 477 log_debug(thread, smr)("tid=" UINTX_FORMAT ": SafeThreadsListPtr::acquire_stable_list: add nested list pointer to ThreadsList=" INTPTR_FORMAT, os::current_thread_id(), p2i(_list)); 478 } 479 480 // Release a stable ThreadsList. 481 // 482 void SafeThreadsListPtr::release_stable_list() { 483 assert(_thread != NULL, "sanity check"); 484 assert(_thread->_threads_list_ptr == this, "sanity check"); 485 _thread->_threads_list_ptr = _previous; 486 487 if (_has_ref_count) { 488 // If a SafeThreadsListPtr has been promoted to use reference counting 489 // due to nesting of ThreadsListHandles, then the reference count must be 490 // decremented, at which point it may be freed. The forgotten value of 491 // the list no longer matters at this point and should already be NULL. 492 assert(_thread->get_threads_hazard_ptr() == NULL, "sanity check"); 493 if (EnableThreadSMRStatistics) { 494 _thread->dec_nested_threads_hazard_ptr_cnt(); 495 } 496 _list->dec_nested_handle_cnt(); 497 498 log_debug(thread, smr)("tid=" UINTX_FORMAT ": SafeThreadsListPtr::release_stable_list: delete nested list pointer to ThreadsList=" INTPTR_FORMAT, os::current_thread_id(), p2i(_list)); 499 } else { 500 // The normal case: a leaf ThreadsListHandle. This merely requires setting 501 // the thread hazard ptr back to NULL. 502 assert(_thread->get_threads_hazard_ptr() != NULL, "sanity check"); 503 _thread->set_threads_hazard_ptr(NULL); 504 } 505 506 // After releasing the hazard ptr, other threads may go ahead and 507 // free up some memory temporarily used by a ThreadsList snapshot. 508 509 // We use double-check locking to reduce traffic on the system 510 // wide Thread-SMR delete_lock. 511 if (ThreadsSMRSupport::delete_notify()) { 512 // An exiting thread might be waiting in smr_delete(); we need to 513 // check with delete_lock to be sure. 514 ThreadsSMRSupport::release_stable_list_wake_up(_has_ref_count); 515 } 516 } 517 518 // Verify that the stable hazard ptr used to safely keep threads 519 // alive is scanned by threads_do() which is a key piece of honoring 520 // the Thread-SMR protocol. 521 void SafeThreadsListPtr::verify_hazard_ptr_scanned() { 522 #ifdef ASSERT 523 assert(_list != NULL, "_list must not be NULL"); 524 525 if (ThreadsSMRSupport::is_bootstrap_list(_list)) { 526 // We are early in VM bootstrapping so nothing to do here. 527 return; 528 } 529 530 // The closure will attempt to verify that the calling thread can 531 // be found by threads_do() on the specified ThreadsList. If it 532 // is successful, then the specified ThreadsList was acquired as 533 // a stable hazard ptr by the calling thread in a way that honored 534 // the Thread-SMR protocol. 535 // 536 // If the calling thread cannot be found by threads_do() and if 537 // it is not the shutdown thread, then the calling thread is not 538 // honoring the Thread-SMR ptotocol. This means that the specified 539 // ThreadsList is not a stable hazard ptr and can be freed by 540 // another thread from the to-be-deleted list at any time. 541 // 542 // Note: The shutdown thread has removed itself from the Threads 543 // list and is safe to have a waiver from this check because 544 // VM_Exit::_shutdown_thread is not set until after the VMThread 545 // has started the final safepoint which holds the Threads_lock 546 // for the remainder of the VM's life. 547 // 548 VerifyHazardPtrThreadClosure cl(_thread); 549 ThreadsSMRSupport::threads_do(&cl, _list); 550 551 // If the calling thread is not honoring the Thread-SMR protocol, 552 // then we will either crash in threads_do() above because 'threads' 553 // was freed by another thread or we will fail the assert() below. 554 // In either case, we won't get past this point with a badly placed 555 // ThreadsListHandle. 556 557 assert(cl.found() || _thread == VM_Exit::shutdown_thread(), "Acquired a ThreadsList snapshot from a thread not recognized by the Thread-SMR protocol."); 558 #endif 559 } 560 561 // 'entries + 1' so we always have at least one entry. 562 ThreadsList::ThreadsList(int entries) : 563 _length(entries), 564 _next_list(NULL), 565 _threads(NEW_C_HEAP_ARRAY(JavaThread*, entries + 1, mtThread)), 566 _nested_handle_cnt(0) 567 { 568 *(JavaThread**)(_threads + entries) = NULL; // Make sure the extra entry is NULL. 569 } 570 571 ThreadsList::~ThreadsList() { 572 FREE_C_HEAP_ARRAY(JavaThread*, _threads); 573 } 574 575 // Add a JavaThread to a ThreadsList. The returned ThreadsList is a 576 // new copy of the specified ThreadsList with the specified JavaThread 577 // appended to the end. 578 ThreadsList *ThreadsList::add_thread(ThreadsList *list, JavaThread *java_thread) { 579 const uint index = list->_length; 580 const uint new_length = index + 1; 581 const uint head_length = index; 582 ThreadsList *const new_list = new ThreadsList(new_length); 583 584 if (head_length > 0) { 585 Copy::disjoint_words((HeapWord*)list->_threads, (HeapWord*)new_list->_threads, head_length); 586 } 587 *(JavaThread**)(new_list->_threads + index) = java_thread; 588 589 return new_list; 590 } 591 592 void ThreadsList::dec_nested_handle_cnt() { 593 // The decrement needs to be MO_ACQ_REL. At the moment, the Atomic::dec 594 // backend on PPC does not yet conform to these requirements. Therefore 595 // the decrement is simulated with an Atomic::sub(1, &addr). 596 // Without this MO_ACQ_REL Atomic::dec simulation, the nested SMR mechanism 597 // is not generally safe to use. 598 Atomic::sub(1, &_nested_handle_cnt); 599 } 600 601 int ThreadsList::find_index_of_JavaThread(JavaThread *target) { 602 if (target == NULL) { 603 return -1; 604 } 605 for (uint i = 0; i < length(); i++) { 606 if (target == thread_at(i)) { 607 return (int)i; 608 } 609 } 610 return -1; 611 } 612 613 JavaThread* ThreadsList::find_JavaThread_from_java_tid(jlong java_tid) const { 614 for (uint i = 0; i < length(); i++) { 615 JavaThread* thread = thread_at(i); 616 oop tobj = thread->threadObj(); 617 // Ignore the thread if it hasn't run yet, has exited 618 // or is starting to exit. 619 if (tobj != NULL && !thread->is_exiting() && 620 java_tid == java_lang_Thread::thread_id(tobj)) { 621 // found a match 622 return thread; 623 } 624 } 625 return NULL; 626 } 627 628 void ThreadsList::inc_nested_handle_cnt() { 629 // The increment needs to be MO_SEQ_CST. At the moment, the Atomic::inc 630 // backend on PPC does not yet conform to these requirements. Therefore 631 // the increment is simulated with a load phi; cas phi + 1; loop. 632 // Without this MO_SEQ_CST Atomic::inc simulation, the nested SMR mechanism 633 // is not generally safe to use. 634 intx sample = OrderAccess::load_acquire(&_nested_handle_cnt); 635 for (;;) { 636 if (Atomic::cmpxchg(sample + 1, &_nested_handle_cnt, sample) == sample) { 637 return; 638 } else { 639 sample = OrderAccess::load_acquire(&_nested_handle_cnt); 640 } 641 } 642 } 643 644 bool ThreadsList::includes(const JavaThread * const p) const { 645 if (p == NULL) { 646 return false; 647 } 648 for (uint i = 0; i < length(); i++) { 649 if (thread_at(i) == p) { 650 return true; 651 } 652 } 653 return false; 654 } 655 656 // Remove a JavaThread from a ThreadsList. The returned ThreadsList is a 657 // new copy of the specified ThreadsList with the specified JavaThread 658 // removed. 659 ThreadsList *ThreadsList::remove_thread(ThreadsList* list, JavaThread* java_thread) { 660 assert(list->_length > 0, "sanity"); 661 662 uint i = (uint)list->find_index_of_JavaThread(java_thread); 663 assert(i < list->_length, "did not find JavaThread on the list"); 664 const uint index = i; 665 const uint new_length = list->_length - 1; 666 const uint head_length = index; 667 const uint tail_length = (new_length >= index) ? (new_length - index) : 0; 668 ThreadsList *const new_list = new ThreadsList(new_length); 669 670 if (head_length > 0) { 671 Copy::disjoint_words((HeapWord*)list->_threads, (HeapWord*)new_list->_threads, head_length); 672 } 673 if (tail_length > 0) { 674 Copy::disjoint_words((HeapWord*)list->_threads + index + 1, (HeapWord*)new_list->_threads + index, tail_length); 675 } 676 677 return new_list; 678 } 679 680 ThreadsListHandle::ThreadsListHandle(Thread *self) : _list_ptr(self, /* acquire */ true) { 681 assert(self == Thread::current(), "sanity check"); 682 if (EnableThreadSMRStatistics) { 683 _timer.start(); 684 } 685 } 686 687 ThreadsListHandle::~ThreadsListHandle() { 688 if (EnableThreadSMRStatistics) { 689 _timer.stop(); 690 uint millis = (uint)_timer.milliseconds(); 691 ThreadsSMRSupport::update_tlh_stats(millis); 692 } 693 } 694 695 // Convert an internal thread reference to a JavaThread found on the 696 // associated ThreadsList. This ThreadsListHandle "protects" the 697 // returned JavaThread *. 698 // 699 // If thread_oop_p is not NULL, then the caller wants to use the oop 700 // after this call so the oop is returned. On success, *jt_pp is set 701 // to the converted JavaThread * and true is returned. On error, 702 // returns false. 703 // 704 bool ThreadsListHandle::cv_internal_thread_to_JavaThread(jobject jthread, 705 JavaThread ** jt_pp, 706 oop * thread_oop_p) { 707 assert(this->list() != NULL, "must have a ThreadsList"); 708 assert(jt_pp != NULL, "must have a return JavaThread pointer"); 709 // thread_oop_p is optional so no assert() 710 711 // The JVM_* interfaces don't allow a NULL thread parameter; JVM/TI 712 // allows a NULL thread parameter to signify "current thread" which 713 // allows us to avoid calling cv_external_thread_to_JavaThread(). 714 // The JVM_* interfaces have no such leeway. 715 716 oop thread_oop = JNIHandles::resolve_non_null(jthread); 717 // Looks like an oop at this point. 718 if (thread_oop_p != NULL) { 719 // Return the oop to the caller; the caller may still want 720 // the oop even if this function returns false. 721 *thread_oop_p = thread_oop; 722 } 723 724 JavaThread *java_thread = java_lang_Thread::thread(thread_oop); 725 if (java_thread == NULL) { 726 // The java.lang.Thread does not contain a JavaThread * so it has 727 // not yet run or it has died. 728 return false; 729 } 730 // Looks like a live JavaThread at this point. 731 732 if (java_thread != JavaThread::current()) { 733 // jthread is not for the current JavaThread so have to verify 734 // the JavaThread * against the ThreadsList. 735 if (EnableThreadSMRExtraValidityChecks && !includes(java_thread)) { 736 // Not on the JavaThreads list so it is not alive. 737 return false; 738 } 739 } 740 741 // Return a live JavaThread that is "protected" by the 742 // ThreadsListHandle in the caller. 743 *jt_pp = java_thread; 744 return true; 745 } 746 747 void ThreadsSMRSupport::add_thread(JavaThread *thread){ 748 ThreadsList *new_list = ThreadsList::add_thread(get_java_thread_list(), thread); 749 if (EnableThreadSMRStatistics) { 750 inc_java_thread_list_alloc_cnt(); 751 update_java_thread_list_max(new_list->length()); 752 } 753 // Initial _java_thread_list will not generate a "Threads::add" mesg. 754 log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::add: new ThreadsList=" INTPTR_FORMAT, os::current_thread_id(), p2i(new_list)); 755 756 ThreadsList *old_list = xchg_java_thread_list(new_list); 757 free_list(old_list); 758 } 759 760 // set_delete_notify() and clear_delete_notify() are called 761 // under the protection of the delete_lock, but we also use an 762 // Atomic operation to ensure the memory update is seen earlier than 763 // when the delete_lock is dropped. 764 // 765 void ThreadsSMRSupport::clear_delete_notify() { 766 Atomic::dec(&_delete_notify); 767 } 768 769 bool ThreadsSMRSupport::delete_notify() { 770 // Use load_acquire() in order to see any updates to _delete_notify 771 // earlier than when delete_lock is grabbed. 772 return (OrderAccess::load_acquire(&_delete_notify) != 0); 773 } 774 775 // Safely free a ThreadsList after a Threads::add() or Threads::remove(). 776 // The specified ThreadsList may not get deleted during this call if it 777 // is still in-use (referenced by a hazard ptr). Other ThreadsLists 778 // in the chain may get deleted by this call if they are no longer in-use. 779 void ThreadsSMRSupport::free_list(ThreadsList* threads) { 780 assert_locked_or_safepoint(Threads_lock); 781 782 if (is_bootstrap_list(threads)) { 783 // The bootstrap list cannot be freed and is empty so 784 // it does not need to be scanned. Nothing to do here. 785 log_debug(thread, smr)("tid=" UINTX_FORMAT ": ThreadsSMRSupport::free_list: bootstrap ThreadsList=" INTPTR_FORMAT " is no longer in use.", os::current_thread_id(), p2i(threads)); 786 return; 787 } 788 789 threads->set_next_list(_to_delete_list); 790 _to_delete_list = threads; 791 if (EnableThreadSMRStatistics) { 792 _to_delete_list_cnt++; 793 if (_to_delete_list_cnt > _to_delete_list_max) { 794 _to_delete_list_max = _to_delete_list_cnt; 795 } 796 } 797 798 // Hash table size should be first power of two higher than twice the length of the ThreadsList 799 int hash_table_size = MIN2((int)get_java_thread_list()->length(), 32) << 1; 800 hash_table_size--; 801 hash_table_size |= hash_table_size >> 1; 802 hash_table_size |= hash_table_size >> 2; 803 hash_table_size |= hash_table_size >> 4; 804 hash_table_size |= hash_table_size >> 8; 805 hash_table_size |= hash_table_size >> 16; 806 hash_table_size++; 807 808 // Gather a hash table of the current hazard ptrs: 809 ThreadScanHashtable *scan_table = new ThreadScanHashtable(hash_table_size); 810 ScanHazardPtrGatherThreadsListClosure scan_cl(scan_table); 811 threads_do(&scan_cl); 812 OrderAccess::acquire(); // Must order reads of hazard ptr before reads of 813 // nested reference counters 814 815 // Walk through the linked list of pending freeable ThreadsLists 816 // and free the ones that are not referenced from hazard ptrs. 817 ThreadsList* current = _to_delete_list; 818 ThreadsList* prev = NULL; 819 ThreadsList* next = NULL; 820 bool threads_is_freed = false; 821 while (current != NULL) { 822 next = current->next_list(); 823 if (!scan_table->has_entry((void*)current) && current->_nested_handle_cnt == 0) { 824 // This ThreadsList is not referenced by a hazard ptr. 825 if (prev != NULL) { 826 prev->set_next_list(next); 827 } 828 if (_to_delete_list == current) { 829 _to_delete_list = next; 830 } 831 832 log_debug(thread, smr)("tid=" UINTX_FORMAT ": ThreadsSMRSupport::free_list: threads=" INTPTR_FORMAT " is freed.", os::current_thread_id(), p2i(current)); 833 if (current == threads) threads_is_freed = true; 834 delete current; 835 if (EnableThreadSMRStatistics) { 836 _java_thread_list_free_cnt++; 837 _to_delete_list_cnt--; 838 } 839 } else { 840 prev = current; 841 } 842 current = next; 843 } 844 845 if (!threads_is_freed) { 846 // Only report "is not freed" on the original call to 847 // free_list() for this ThreadsList. 848 log_debug(thread, smr)("tid=" UINTX_FORMAT ": ThreadsSMRSupport::free_list: threads=" INTPTR_FORMAT " is not freed.", os::current_thread_id(), p2i(threads)); 849 } 850 851 delete scan_table; 852 } 853 854 // Return true if the specified JavaThread is protected by a hazard 855 // pointer (ThreadsList reference). Otherwise, returns false. 856 // 857 bool ThreadsSMRSupport::is_a_protected_JavaThread(JavaThread *thread) { 858 assert_locked_or_safepoint(Threads_lock); 859 860 // Hash table size should be first power of two higher than twice 861 // the length of the Threads list. 862 int hash_table_size = MIN2((int)get_java_thread_list()->length(), 32) << 1; 863 hash_table_size--; 864 hash_table_size |= hash_table_size >> 1; 865 hash_table_size |= hash_table_size >> 2; 866 hash_table_size |= hash_table_size >> 4; 867 hash_table_size |= hash_table_size >> 8; 868 hash_table_size |= hash_table_size >> 16; 869 hash_table_size++; 870 871 // Gather a hash table of the JavaThreads indirectly referenced by 872 // hazard ptrs. 873 ThreadScanHashtable *scan_table = new ThreadScanHashtable(hash_table_size); 874 ScanHazardPtrGatherProtectedThreadsClosure scan_cl(scan_table); 875 threads_do(&scan_cl); 876 OrderAccess::acquire(); // Must order reads of hazard ptr before reads of 877 // nested reference counters 878 879 // Walk through the linked list of pending freeable ThreadsLists 880 // and include the ones that are currently in use by a nested 881 // ThreadsListHandle in the search set. 882 ThreadsList* current = _to_delete_list; 883 while (current != NULL) { 884 if (current->_nested_handle_cnt != 0) { 885 // 'current' is in use by a nested ThreadsListHandle so the hazard 886 // ptr is protecting all the JavaThreads on that ThreadsList. 887 AddThreadHazardPointerThreadClosure add_cl(scan_table); 888 current->threads_do(&add_cl); 889 } 890 current = current->next_list(); 891 } 892 893 bool thread_is_protected = false; 894 if (scan_table->has_entry((void*)thread)) { 895 thread_is_protected = true; 896 } 897 delete scan_table; 898 return thread_is_protected; 899 } 900 901 // Wake up portion of the release stable ThreadsList protocol; 902 // uses the delete_lock(). 903 // 904 void ThreadsSMRSupport::release_stable_list_wake_up(bool is_nested) { 905 const char* log_str = is_nested ? "nested hazard ptr" : "regular hazard ptr"; 906 907 // Note: delete_lock is held in smr_delete() for the entire 908 // hazard ptr search so that we do not lose this notify() if 909 // the exiting thread has to wait. That code path also holds 910 // Threads_lock (which was grabbed before delete_lock) so that 911 // threads_do() can be called. This means the system can't start a 912 // safepoint which means this thread can't take too long to get to 913 // a safepoint because of being blocked on delete_lock. 914 // 915 MonitorLockerEx ml(ThreadsSMRSupport::delete_lock(), Monitor::_no_safepoint_check_flag); 916 if (ThreadsSMRSupport::delete_notify()) { 917 // Notify any exiting JavaThreads that are waiting in smr_delete() 918 // that we've released a ThreadsList. 919 ml.notify_all(); 920 log_debug(thread, smr)("tid=" UINTX_FORMAT ": ThreadsSMRSupport::release_stable_list notified %s", os::current_thread_id(), log_str); 921 } 922 } 923 924 void ThreadsSMRSupport::remove_thread(JavaThread *thread) { 925 ThreadsList *new_list = ThreadsList::remove_thread(ThreadsSMRSupport::get_java_thread_list(), thread); 926 if (EnableThreadSMRStatistics) { 927 ThreadsSMRSupport::inc_java_thread_list_alloc_cnt(); 928 // This list is smaller so no need to check for a "longest" update. 929 } 930 931 // Final _java_thread_list will not generate a "Threads::remove" mesg. 932 log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::remove: new ThreadsList=" INTPTR_FORMAT, os::current_thread_id(), p2i(new_list)); 933 934 ThreadsList *old_list = ThreadsSMRSupport::xchg_java_thread_list(new_list); 935 ThreadsSMRSupport::free_list(old_list); 936 } 937 938 // See note for clear_delete_notify(). 939 // 940 void ThreadsSMRSupport::set_delete_notify() { 941 Atomic::inc(&_delete_notify); 942 } 943 944 // Safely delete a JavaThread when it is no longer in use by a 945 // ThreadsListHandle. 946 // 947 void ThreadsSMRSupport::smr_delete(JavaThread *thread) { 948 assert(!Threads_lock->owned_by_self(), "sanity"); 949 950 bool has_logged_once = false; 951 elapsedTimer timer; 952 if (EnableThreadSMRStatistics) { 953 timer.start(); 954 } 955 956 while (true) { 957 { 958 // No safepoint check because this JavaThread is not on the 959 // Threads list. 960 MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag); 961 // Cannot use a MonitorLockerEx helper here because we have 962 // to drop the Threads_lock first if we wait. 963 ThreadsSMRSupport::delete_lock()->lock_without_safepoint_check(); 964 // Set the delete_notify flag after we grab delete_lock 965 // and before we scan hazard ptrs because we're doing 966 // double-check locking in release_stable_list(). 967 ThreadsSMRSupport::set_delete_notify(); 968 969 if (!is_a_protected_JavaThread(thread)) { 970 // This is the common case. 971 ThreadsSMRSupport::clear_delete_notify(); 972 ThreadsSMRSupport::delete_lock()->unlock(); 973 break; 974 } 975 if (!has_logged_once) { 976 has_logged_once = true; 977 log_debug(thread, smr)("tid=" UINTX_FORMAT ": ThreadsSMRSupport::smr_delete: thread=" INTPTR_FORMAT " is not deleted.", os::current_thread_id(), p2i(thread)); 978 if (log_is_enabled(Debug, os, thread)) { 979 ScanHazardPtrPrintMatchingThreadsClosure scan_cl(thread); 980 threads_do(&scan_cl); 981 ThreadsList* current = _to_delete_list; 982 while (current != NULL) { 983 if (current->_nested_handle_cnt != 0 && current->includes(thread)) { 984 log_debug(thread, smr)("tid=" UINTX_FORMAT ": ThreadsSMRSupport::smr_delete: found nested hazard pointer to thread=" INTPTR_FORMAT, os::current_thread_id(), p2i(thread)); 985 } 986 current = current->next_list(); 987 } 988 } 989 } 990 } // We have to drop the Threads_lock to wait or delete the thread 991 992 if (EnableThreadSMRStatistics) { 993 _delete_lock_wait_cnt++; 994 if (_delete_lock_wait_cnt > _delete_lock_wait_max) { 995 _delete_lock_wait_max = _delete_lock_wait_cnt; 996 } 997 } 998 // Wait for a release_stable_list() call before we check again. No 999 // safepoint check, no timeout, and not as suspend equivalent flag 1000 // because this JavaThread is not on the Threads list. 1001 ThreadsSMRSupport::delete_lock()->wait(Mutex::_no_safepoint_check_flag, 0, 1002 !Mutex::_as_suspend_equivalent_flag); 1003 if (EnableThreadSMRStatistics) { 1004 _delete_lock_wait_cnt--; 1005 } 1006 1007 ThreadsSMRSupport::clear_delete_notify(); 1008 ThreadsSMRSupport::delete_lock()->unlock(); 1009 // Retry the whole scenario. 1010 } 1011 1012 delete thread; 1013 if (EnableThreadSMRStatistics) { 1014 timer.stop(); 1015 uint millis = (uint)timer.milliseconds(); 1016 ThreadsSMRSupport::inc_deleted_thread_cnt(); 1017 ThreadsSMRSupport::add_deleted_thread_times(millis); 1018 ThreadsSMRSupport::update_deleted_thread_time_max(millis); 1019 } 1020 1021 log_debug(thread, smr)("tid=" UINTX_FORMAT ": ThreadsSMRSupport::smr_delete: thread=" INTPTR_FORMAT " is deleted.", os::current_thread_id(), p2i(thread)); 1022 } 1023 1024 // Apply the closure to all threads in the system, with a snapshot of 1025 // all JavaThreads provided by the list parameter. 1026 void ThreadsSMRSupport::threads_do(ThreadClosure *tc, ThreadsList *list) { 1027 list->threads_do(tc); 1028 Threads::non_java_threads_do(tc); 1029 } 1030 1031 // Apply the closure to all threads in the system. 1032 void ThreadsSMRSupport::threads_do(ThreadClosure *tc) { 1033 threads_do(tc, _java_thread_list); 1034 } 1035 1036 1037 // Debug, logging, and printing stuff at the end: 1038 1039 // Print SMR info for a SafeThreadsListPtr to a given output stream. 1040 void SafeThreadsListPtr::print_on(outputStream* st) { 1041 if (this == _thread->_threads_list_ptr) { 1042 // The top level hazard ptr. 1043 st->print(" _threads_hazard_ptr=" INTPTR_FORMAT, p2i(_list)); 1044 } else { 1045 // Nested hazard ptrs. 1046 st->print(", _nested_threads_hazard_ptr=" INTPTR_FORMAT, p2i(_list)); 1047 } 1048 } 1049 1050 // Log Threads class SMR info. 1051 void ThreadsSMRSupport::log_statistics() { 1052 LogTarget(Info, thread, smr) log; 1053 if (log.is_enabled()) { 1054 LogStream out(log); 1055 print_info_on(&out); 1056 } 1057 } 1058 1059 // Print SMR info for a thread to a given output stream. 1060 void ThreadsSMRSupport::print_info_on(const Thread* thread, outputStream* st) { 1061 if (thread->_threads_hazard_ptr != NULL) { 1062 st->print(" _threads_hazard_ptr=" INTPTR_FORMAT, p2i(thread->_threads_hazard_ptr)); 1063 } 1064 if (EnableThreadSMRStatistics && thread->_threads_list_ptr != NULL) { 1065 // The count is only interesting if we have a _threads_list_ptr. 1066 st->print(", _nested_threads_hazard_ptr_cnt=%u", thread->_nested_threads_hazard_ptr_cnt); 1067 } 1068 if (SafepointSynchronize::is_at_safepoint() || Thread::current() == thread) { 1069 // It is only safe to walk the list if we're at a safepoint or the 1070 // calling thread is walking its own list. 1071 SafeThreadsListPtr* current = thread->_threads_list_ptr; 1072 if (current != NULL) { 1073 // Skip the top nesting level as it is always printed above. 1074 current = current->previous(); 1075 } 1076 while (current != NULL) { 1077 current->print_on(st); 1078 current = current->previous(); 1079 } 1080 } 1081 } 1082 1083 // Print Threads class SMR info. 1084 void ThreadsSMRSupport::print_info_on(outputStream* st) { 1085 // Only grab the Threads_lock if we don't already own it and if we 1086 // are not reporting an error. 1087 // Note: Not grabbing the Threads_lock during error reporting is 1088 // dangerous because the data structures we want to print can be 1089 // freed concurrently. However, grabbing the Threads_lock during 1090 // error reporting can be equally dangerous since this thread might 1091 // block during error reporting or a nested error could leave the 1092 // Threads_lock held. The classic no win scenario. 1093 // 1094 MutexLockerEx ml((Threads_lock->owned_by_self() || VMError::is_error_reported()) ? NULL : Threads_lock); 1095 1096 st->print_cr("Threads class SMR info:"); 1097 st->print_cr("_java_thread_list=" INTPTR_FORMAT ", length=%u, " 1098 "elements={", p2i(_java_thread_list), 1099 _java_thread_list->length()); 1100 print_info_elements_on(st, _java_thread_list); 1101 st->print_cr("}"); 1102 if (_to_delete_list != NULL) { 1103 st->print_cr("_to_delete_list=" INTPTR_FORMAT ", length=%u, " 1104 "elements={", p2i(_to_delete_list), 1105 _to_delete_list->length()); 1106 print_info_elements_on(st, _to_delete_list); 1107 st->print_cr("}"); 1108 for (ThreadsList *t_list = _to_delete_list->next_list(); 1109 t_list != NULL; t_list = t_list->next_list()) { 1110 st->print("next-> " INTPTR_FORMAT ", length=%u, " 1111 "elements={", p2i(t_list), t_list->length()); 1112 print_info_elements_on(st, t_list); 1113 st->print_cr("}"); 1114 } 1115 } 1116 if (!EnableThreadSMRStatistics) { 1117 return; 1118 } 1119 st->print_cr("_java_thread_list_alloc_cnt=" UINT64_FORMAT ", " 1120 "_java_thread_list_free_cnt=" UINT64_FORMAT ", " 1121 "_java_thread_list_max=%u, " 1122 "_nested_thread_list_max=%u", 1123 _java_thread_list_alloc_cnt, 1124 _java_thread_list_free_cnt, 1125 _java_thread_list_max, 1126 _nested_thread_list_max); 1127 if (_tlh_cnt > 0) { 1128 st->print_cr("_tlh_cnt=%u" 1129 ", _tlh_times=%u" 1130 ", avg_tlh_time=%0.2f" 1131 ", _tlh_time_max=%u", 1132 _tlh_cnt, _tlh_times, 1133 ((double) _tlh_times / _tlh_cnt), 1134 _tlh_time_max); 1135 } 1136 if (_deleted_thread_cnt > 0) { 1137 st->print_cr("_deleted_thread_cnt=%u" 1138 ", _deleted_thread_times=%u" 1139 ", avg_deleted_thread_time=%0.2f" 1140 ", _deleted_thread_time_max=%u", 1141 _deleted_thread_cnt, _deleted_thread_times, 1142 ((double) _deleted_thread_times / _deleted_thread_cnt), 1143 _deleted_thread_time_max); 1144 } 1145 st->print_cr("_delete_lock_wait_cnt=%u, _delete_lock_wait_max=%u", 1146 _delete_lock_wait_cnt, _delete_lock_wait_max); 1147 st->print_cr("_to_delete_list_cnt=%u, _to_delete_list_max=%u", 1148 _to_delete_list_cnt, _to_delete_list_max); 1149 } 1150 1151 // Print ThreadsList elements (4 per line). 1152 void ThreadsSMRSupport::print_info_elements_on(outputStream* st, ThreadsList* t_list) { 1153 uint cnt = 0; 1154 JavaThreadIterator jti(t_list); 1155 for (JavaThread *jt = jti.first(); jt != NULL; jt = jti.next()) { 1156 st->print(INTPTR_FORMAT, p2i(jt)); 1157 if (cnt < t_list->length() - 1) { 1158 // Separate with comma or comma-space except for the last one. 1159 if (((cnt + 1) % 4) == 0) { 1160 // Four INTPTR_FORMAT fit on an 80 column line so end the 1161 // current line with just a comma. 1162 st->print_cr(","); 1163 } else { 1164 // Not the last one on the current line so use comma-space: 1165 st->print(", "); 1166 } 1167 } else { 1168 // Last one so just end the current line. 1169 st->cr(); 1170 } 1171 cnt++; 1172 } 1173 }