1 /* 2 * Copyright (c) 2017, 2019, 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/sharedRuntime.hpp" 30 #include "runtime/thread.inline.hpp" 31 #include "runtime/threadSMR.inline.hpp" 32 #include "runtime/vmOperations.hpp" 33 #include "services/threadIdTable.hpp" 34 #include "services/threadService.hpp" 35 #include "utilities/copy.hpp" 36 #include "utilities/globalDefinitions.hpp" 37 #include "utilities/ostream.hpp" 38 #include "utilities/resourceHash.hpp" 39 #include "utilities/vmError.hpp" 40 41 // The '_cnt', '_max' and '_times" fields are enabled via 42 // -XX:+EnableThreadSMRStatistics: 43 44 // # of parallel threads in _delete_lock->wait(). 45 // Impl note: Hard to imagine > 64K waiting threads so this could be 16-bit, 46 // but there is no nice 16-bit _FORMAT support. 47 uint ThreadsSMRSupport::_delete_lock_wait_cnt = 0; 48 49 // Max # of parallel threads in _delete_lock->wait(). 50 // Impl note: See _delete_lock_wait_cnt note. 51 uint ThreadsSMRSupport::_delete_lock_wait_max = 0; 52 53 // Flag to indicate when an _delete_lock->notify() is needed. 54 // Impl note: See _delete_lock_wait_cnt note. 55 volatile uint ThreadsSMRSupport::_delete_notify = 0; 56 57 // # of threads deleted over VM lifetime. 58 // Impl note: Atomically incremented over VM lifetime so use unsigned for more 59 // range. Unsigned 64-bit would be more future proof, but 64-bit atomic inc 60 // isn't available everywhere (or is it?). 61 volatile uint ThreadsSMRSupport::_deleted_thread_cnt = 0; 62 63 // Max time in millis to delete a thread. 64 // Impl note: 16-bit might be too small on an overloaded machine. Use 65 // unsigned since this is a time value. Set via Atomic::cmpxchg() in a 66 // loop for correctness. 67 volatile uint ThreadsSMRSupport::_deleted_thread_time_max = 0; 68 69 // Cumulative time in millis to delete threads. 70 // Impl note: Atomically added to over VM lifetime so use unsigned for more 71 // range. Unsigned 64-bit would be more future proof, but 64-bit atomic inc 72 // isn't available everywhere (or is it?). 73 volatile uint ThreadsSMRSupport::_deleted_thread_times = 0; 74 75 // The bootstrap list is empty and cannot be freed. 76 ThreadsList ThreadsSMRSupport::_bootstrap_list = ThreadsList(0); 77 78 // This is the VM's current "threads list" and it contains all of 79 // the JavaThreads the VM considers to be alive at this moment in 80 // time. The other ThreadsList objects in the VM contain past 81 // snapshots of the "threads list". _java_thread_list is initially 82 // set to _bootstrap_list so that we can detect when we have a very 83 // early use of a ThreadsListHandle. 84 ThreadsList* volatile ThreadsSMRSupport::_java_thread_list = &_bootstrap_list; 85 86 // # of ThreadsLists allocated over VM lifetime. 87 // Impl note: We allocate a new ThreadsList for every thread create and 88 // every thread delete so we need a bigger type than the 89 // _deleted_thread_cnt field. 90 uint64_t ThreadsSMRSupport::_java_thread_list_alloc_cnt = 1; 91 92 // # of ThreadsLists freed over VM lifetime. 93 // Impl note: See _java_thread_list_alloc_cnt note. 94 uint64_t ThreadsSMRSupport::_java_thread_list_free_cnt = 0; 95 96 // Max size ThreadsList allocated. 97 // Impl note: Max # of threads alive at one time should fit in unsigned 32-bit. 98 uint ThreadsSMRSupport::_java_thread_list_max = 0; 99 100 // Max # of nested ThreadsLists for a thread. 101 // Impl note: Hard to imagine > 64K nested ThreadsLists so this could be 102 // 16-bit, but there is no nice 16-bit _FORMAT support. 103 uint ThreadsSMRSupport::_nested_thread_list_max = 0; 104 105 // # of ThreadsListHandles deleted over VM lifetime. 106 // Impl note: Atomically incremented over VM lifetime so use unsigned for 107 // more range. There will be fewer ThreadsListHandles than threads so 108 // unsigned 32-bit should be fine. 109 volatile uint ThreadsSMRSupport::_tlh_cnt = 0; 110 111 // Max time in millis to delete a ThreadsListHandle. 112 // Impl note: 16-bit might be too small on an overloaded machine. Use 113 // unsigned since this is a time value. Set via Atomic::cmpxchg() in a 114 // loop for correctness. 115 volatile uint ThreadsSMRSupport::_tlh_time_max = 0; 116 117 // Cumulative time in millis to delete ThreadsListHandles. 118 // Impl note: Atomically added to over VM lifetime so use unsigned for more 119 // range. Unsigned 64-bit would be more future proof, but 64-bit atomic inc 120 // isn't available everywhere (or is it?). 121 volatile uint ThreadsSMRSupport::_tlh_times = 0; 122 123 ThreadsList* ThreadsSMRSupport::_to_delete_list = NULL; 124 125 // # of parallel ThreadsLists on the to-delete list. 126 // Impl note: Hard to imagine > 64K ThreadsLists needing to be deleted so 127 // this could be 16-bit, but there is no nice 16-bit _FORMAT support. 128 uint ThreadsSMRSupport::_to_delete_list_cnt = 0; 129 130 // Max # of parallel ThreadsLists on the to-delete list. 131 // Impl note: See _to_delete_list_cnt note. 132 uint ThreadsSMRSupport::_to_delete_list_max = 0; 133 134 // 'inline' functions first so the definitions are before first use: 135 136 inline void ThreadsSMRSupport::add_deleted_thread_times(uint add_value) { 137 Atomic::add(&_deleted_thread_times, add_value); 138 } 139 140 inline void ThreadsSMRSupport::inc_deleted_thread_cnt() { 141 Atomic::inc(&_deleted_thread_cnt); 142 } 143 144 inline void ThreadsSMRSupport::inc_java_thread_list_alloc_cnt() { 145 _java_thread_list_alloc_cnt++; 146 } 147 148 inline bool ThreadsSMRSupport::is_bootstrap_list(ThreadsList* list) { 149 return list == &_bootstrap_list; 150 } 151 152 inline void ThreadsSMRSupport::update_deleted_thread_time_max(uint new_value) { 153 while (true) { 154 uint cur_value = _deleted_thread_time_max; 155 if (new_value <= cur_value) { 156 // No need to update max value so we're done. 157 break; 158 } 159 if (Atomic::cmpxchg(new_value, &_deleted_thread_time_max, cur_value) == cur_value) { 160 // Updated max value so we're done. Otherwise try it all again. 161 break; 162 } 163 } 164 } 165 166 inline void ThreadsSMRSupport::update_java_thread_list_max(uint new_value) { 167 if (new_value > _java_thread_list_max) { 168 _java_thread_list_max = new_value; 169 } 170 } 171 172 inline ThreadsList* ThreadsSMRSupport::xchg_java_thread_list(ThreadsList* new_list) { 173 return (ThreadsList*)Atomic::xchg(&_java_thread_list, new_list); 174 } 175 176 // Hash table of pointers found by a scan. Used for collecting hazard 177 // pointers (ThreadsList references). Also used for collecting JavaThreads 178 // that are indirectly referenced by hazard ptrs. An instance of this 179 // class only contains one type of pointer. 180 // 181 class ThreadScanHashtable : public CHeapObj<mtThread> { 182 private: 183 static bool ptr_equals(void * const& s1, void * const& s2) { 184 return s1 == s2; 185 } 186 187 static unsigned int ptr_hash(void * const& s1) { 188 // 2654435761 = 2^32 * Phi (golden ratio) 189 return (unsigned int)(((uint32_t)(uintptr_t)s1) * 2654435761u); 190 } 191 192 int _table_size; 193 // ResourceHashtable SIZE is specified at compile time so our 194 // dynamic _table_size is unused for now; 1031 is the first prime 195 // after 1024. 196 typedef ResourceHashtable<void *, int, &ThreadScanHashtable::ptr_hash, 197 &ThreadScanHashtable::ptr_equals, 1031, 198 ResourceObj::C_HEAP, mtThread> PtrTable; 199 PtrTable * _ptrs; 200 201 public: 202 // ResourceHashtable is passed to various functions and populated in 203 // different places so we allocate it using C_HEAP to make it immune 204 // from any ResourceMarks that happen to be in the code paths. 205 ThreadScanHashtable(int table_size) : _table_size(table_size), _ptrs(new (ResourceObj::C_HEAP, mtThread) PtrTable()) {} 206 207 ~ThreadScanHashtable() { delete _ptrs; } 208 209 bool has_entry(void *pointer) { 210 int *val_ptr = _ptrs->get(pointer); 211 return val_ptr != NULL && *val_ptr == 1; 212 } 213 214 void add_entry(void *pointer) { 215 _ptrs->put(pointer, 1); 216 } 217 }; 218 219 // Closure to gather JavaThreads indirectly referenced by hazard ptrs 220 // (ThreadsList references) into a hash table. This closure handles part 2 221 // of the dance - adding all the JavaThreads referenced by the hazard 222 // pointer (ThreadsList reference) to the hash table. 223 // 224 class AddThreadHazardPointerThreadClosure : public ThreadClosure { 225 private: 226 ThreadScanHashtable *_table; 227 228 public: 229 AddThreadHazardPointerThreadClosure(ThreadScanHashtable *table) : _table(table) {} 230 231 virtual void do_thread(Thread *thread) { 232 if (!_table->has_entry((void*)thread)) { 233 // The same JavaThread might be on more than one ThreadsList or 234 // more than one thread might be using the same ThreadsList. In 235 // either case, we only need a single entry for a JavaThread. 236 _table->add_entry((void*)thread); 237 } 238 } 239 }; 240 241 // Closure to gather JavaThreads indirectly referenced by hazard ptrs 242 // (ThreadsList references) into a hash table. This closure handles part 1 243 // of the dance - hazard ptr chain walking and dispatch to another 244 // closure. 245 // 246 class ScanHazardPtrGatherProtectedThreadsClosure : public ThreadClosure { 247 private: 248 ThreadScanHashtable *_table; 249 public: 250 ScanHazardPtrGatherProtectedThreadsClosure(ThreadScanHashtable *table) : _table(table) {} 251 252 virtual void do_thread(Thread *thread) { 253 assert_locked_or_safepoint(Threads_lock); 254 255 if (thread == NULL) return; 256 257 // This code races with ThreadsSMRSupport::acquire_stable_list() which 258 // is lock-free so we have to handle some special situations. 259 // 260 ThreadsList *current_list = NULL; 261 while (true) { 262 current_list = thread->get_threads_hazard_ptr(); 263 // No hazard ptr so nothing more to do. 264 if (current_list == NULL) { 265 return; 266 } 267 268 // If the hazard ptr is verified as stable (since it is not tagged), 269 // then it is safe to use. 270 if (!Thread::is_hazard_ptr_tagged(current_list)) break; 271 272 // The hazard ptr is tagged as not yet verified as being stable 273 // so we are racing with acquire_stable_list(). This exchange 274 // attempts to invalidate the hazard ptr. If we win the race, 275 // then we can ignore this unstable hazard ptr and the other 276 // thread will retry the attempt to publish a stable hazard ptr. 277 // If we lose the race, then we retry our attempt to look at the 278 // hazard ptr. 279 if (thread->cmpxchg_threads_hazard_ptr(NULL, current_list) == current_list) return; 280 } 281 282 // The current JavaThread has a hazard ptr (ThreadsList reference) 283 // which might be _java_thread_list or it might be an older 284 // ThreadsList that has been removed but not freed. In either case, 285 // the hazard ptr is protecting all the JavaThreads on that 286 // ThreadsList. 287 AddThreadHazardPointerThreadClosure add_cl(_table); 288 current_list->threads_do(&add_cl); 289 } 290 }; 291 292 // Closure to gather hazard ptrs (ThreadsList references) into a hash table. 293 // 294 class ScanHazardPtrGatherThreadsListClosure : public ThreadClosure { 295 private: 296 ThreadScanHashtable *_table; 297 public: 298 ScanHazardPtrGatherThreadsListClosure(ThreadScanHashtable *table) : _table(table) {} 299 300 virtual void do_thread(Thread* thread) { 301 assert_locked_or_safepoint(Threads_lock); 302 303 if (thread == NULL) return; 304 ThreadsList *threads = thread->get_threads_hazard_ptr(); 305 if (threads == NULL) { 306 return; 307 } 308 // In this closure we always ignore the tag that might mark this 309 // hazard ptr as not yet verified. If we happen to catch an 310 // unverified hazard ptr that is subsequently discarded (not 311 // published), then the only side effect is that we might keep a 312 // to-be-deleted ThreadsList alive a little longer. 313 threads = Thread::untag_hazard_ptr(threads); 314 if (!_table->has_entry((void*)threads)) { 315 _table->add_entry((void*)threads); 316 } 317 } 318 }; 319 320 // Closure to print JavaThreads that have a hazard ptr (ThreadsList 321 // reference) that contains an indirect reference to a specific JavaThread. 322 // 323 class ScanHazardPtrPrintMatchingThreadsClosure : public ThreadClosure { 324 private: 325 JavaThread *_thread; 326 public: 327 ScanHazardPtrPrintMatchingThreadsClosure(JavaThread *thread) : _thread(thread) {} 328 329 virtual void do_thread(Thread *thread) { 330 assert_locked_or_safepoint(Threads_lock); 331 332 if (thread == NULL) return; 333 ThreadsList *current_list = thread->get_threads_hazard_ptr(); 334 if (current_list == NULL) { 335 return; 336 } 337 // If the hazard ptr is unverified, then ignore it. 338 if (Thread::is_hazard_ptr_tagged(current_list)) return; 339 340 // The current JavaThread has a hazard ptr (ThreadsList reference) 341 // which might be _java_thread_list or it might be an older 342 // ThreadsList that has been removed but not freed. In either case, 343 // the hazard ptr is protecting all the JavaThreads on that 344 // ThreadsList, but we only care about matching a specific JavaThread. 345 JavaThreadIterator jti(current_list); 346 for (JavaThread *p = jti.first(); p != NULL; p = jti.next()) { 347 if (p == _thread) { 348 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)); 349 break; 350 } 351 } 352 } 353 }; 354 355 // Closure to determine if the specified JavaThread is found by 356 // threads_do(). 357 // 358 class VerifyHazardPtrThreadClosure : public ThreadClosure { 359 private: 360 bool _found; 361 Thread *_self; 362 363 public: 364 VerifyHazardPtrThreadClosure(Thread *self) : _found(false), _self(self) {} 365 366 bool found() const { return _found; } 367 368 virtual void do_thread(Thread *thread) { 369 if (thread == _self) { 370 _found = true; 371 } 372 } 373 }; 374 375 376 // Acquire a stable ThreadsList. 377 // 378 void SafeThreadsListPtr::acquire_stable_list() { 379 assert(_thread != NULL, "sanity check"); 380 _needs_release = true; 381 _previous = _thread->_threads_list_ptr; 382 _thread->_threads_list_ptr = this; 383 384 if (_thread->get_threads_hazard_ptr() == NULL) { 385 // The typical case is first. 386 acquire_stable_list_fast_path(); 387 return; 388 } 389 390 // The nested case is rare. 391 acquire_stable_list_nested_path(); 392 } 393 394 // Fast path way to acquire a stable ThreadsList. 395 // 396 void SafeThreadsListPtr::acquire_stable_list_fast_path() { 397 assert(_thread != NULL, "sanity check"); 398 assert(_thread->get_threads_hazard_ptr() == NULL, "sanity check"); 399 400 ThreadsList* threads; 401 402 // Stable recording of a hazard ptr for SMR. This code does not use 403 // locks so its use of the _smr_java_thread_list & _threads_hazard_ptr 404 // fields is racy relative to code that uses those fields with locks. 405 // OrderAccess and Atomic functions are used to deal with those races. 406 // 407 while (true) { 408 threads = ThreadsSMRSupport::get_java_thread_list(); 409 410 // Publish a tagged hazard ptr to denote that the hazard ptr is not 411 // yet verified as being stable. Due to the fence after the hazard 412 // ptr write, it will be sequentially consistent w.r.t. the 413 // sequentially consistent writes of the ThreadsList, even on 414 // non-multiple copy atomic machines where stores can be observed 415 // in different order from different observer threads. 416 ThreadsList* unverified_threads = Thread::tag_hazard_ptr(threads); 417 _thread->set_threads_hazard_ptr(unverified_threads); 418 419 // If _smr_java_thread_list has changed, we have lost a race with 420 // Threads::add() or Threads::remove() and have to try again. 421 if (ThreadsSMRSupport::get_java_thread_list() != threads) { 422 continue; 423 } 424 425 // We try to remove the tag which will verify the hazard ptr as 426 // being stable. This exchange can race with a scanning thread 427 // which might invalidate the tagged hazard ptr to keep it from 428 // being followed to access JavaThread ptrs. If we lose the race, 429 // we simply retry. If we win the race, then the stable hazard 430 // ptr is officially published. 431 if (_thread->cmpxchg_threads_hazard_ptr(threads, unverified_threads) == unverified_threads) { 432 break; 433 } 434 } 435 436 // A stable hazard ptr has been published letting other threads know 437 // that the ThreadsList and the JavaThreads reachable from this list 438 // are protected and hence they should not be deleted until everyone 439 // agrees it is safe to do so. 440 441 _list = threads; 442 443 verify_hazard_ptr_scanned(); 444 } 445 446 // Acquire a nested stable ThreadsList; this is rare so it uses 447 // reference counting. 448 // 449 void SafeThreadsListPtr::acquire_stable_list_nested_path() { 450 assert(_thread != NULL, "sanity check"); 451 assert(_thread->get_threads_hazard_ptr() != NULL, 452 "cannot have a NULL regular hazard ptr when acquiring a nested hazard ptr"); 453 454 // The thread already has a hazard ptr (ThreadsList ref) so we need 455 // to create a nested ThreadsListHandle with the current ThreadsList 456 // since it might be different than our current hazard ptr. To remedy 457 // the situation, the ThreadsList pointed to by the pre-existing 458 // stable hazard ptr is reference counted before the hazard ptr may 459 // be released and moved to a new ThreadsList. The old ThreadsList 460 // is remembered in the ThreadsListHandle. 461 462 ThreadsList* current_list = _previous->_list; 463 if (EnableThreadSMRStatistics) { 464 _thread->inc_nested_threads_hazard_ptr_cnt(); 465 } 466 current_list->inc_nested_handle_cnt(); 467 _previous->_has_ref_count = true; // promote SafeThreadsListPtr to be reference counted 468 _thread->_threads_hazard_ptr = NULL; // clear the hazard ptr so we can go through the fast path below 469 470 if (EnableThreadSMRStatistics && _thread->nested_threads_hazard_ptr_cnt() > ThreadsSMRSupport::_nested_thread_list_max) { 471 ThreadsSMRSupport::_nested_thread_list_max = _thread->nested_threads_hazard_ptr_cnt(); 472 } 473 474 acquire_stable_list_fast_path(); 475 476 verify_hazard_ptr_scanned(); 477 478 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)); 479 } 480 481 // Release a stable ThreadsList. 482 // 483 void SafeThreadsListPtr::release_stable_list() { 484 assert(_thread != NULL, "sanity check"); 485 assert(_thread->_threads_list_ptr == this, "sanity check"); 486 _thread->_threads_list_ptr = _previous; 487 488 if (_has_ref_count) { 489 // If a SafeThreadsListPtr has been promoted to use reference counting 490 // due to nesting of ThreadsListHandles, then the reference count must be 491 // decremented, at which point it may be freed. The forgotten value of 492 // the list no longer matters at this point and should already be NULL. 493 assert(_thread->get_threads_hazard_ptr() == NULL, "sanity check"); 494 if (EnableThreadSMRStatistics) { 495 _thread->dec_nested_threads_hazard_ptr_cnt(); 496 } 497 _list->dec_nested_handle_cnt(); 498 499 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)); 500 } else { 501 // The normal case: a leaf ThreadsListHandle. This merely requires setting 502 // the thread hazard ptr back to NULL. 503 assert(_thread->get_threads_hazard_ptr() != NULL, "sanity check"); 504 _thread->set_threads_hazard_ptr(NULL); 505 } 506 507 // After releasing the hazard ptr, other threads may go ahead and 508 // free up some memory temporarily used by a ThreadsList snapshot. 509 510 // We use double-check locking to reduce traffic on the system 511 // wide Thread-SMR delete_lock. 512 if (ThreadsSMRSupport::delete_notify()) { 513 // An exiting thread might be waiting in smr_delete(); we need to 514 // check with delete_lock to be sure. 515 ThreadsSMRSupport::release_stable_list_wake_up(_has_ref_count); 516 } 517 } 518 519 // Verify that the stable hazard ptr used to safely keep threads 520 // alive is scanned by threads_do() which is a key piece of honoring 521 // the Thread-SMR protocol. 522 void SafeThreadsListPtr::verify_hazard_ptr_scanned() { 523 #ifdef ASSERT 524 assert(_list != NULL, "_list must not be NULL"); 525 526 if (ThreadsSMRSupport::is_bootstrap_list(_list)) { 527 // We are early in VM bootstrapping so nothing to do here. 528 return; 529 } 530 531 if ( _thread == VM_Exit::shutdown_thread()) { 532 // The shutdown thread has removed itself from the Threads 533 // list and is safe to have a waiver from this check because 534 // VM_Exit::_shutdown_thread is not set until after the VMThread 535 // has started the final safepoint which holds the Threads_lock 536 // for the remainder of the VM's life. 537 return; 538 } 539 540 if (VMError::is_error_reported() && 541 VMError::get_first_error_tid() == os::current_thread_id()) { 542 // If there is an error reported by this thread it may use ThreadsList even 543 // if it's unsafe. 544 return; 545 } 546 547 // The closure will attempt to verify that the calling thread can 548 // be found by threads_do() on the specified ThreadsList. If it 549 // is successful, then the specified ThreadsList was acquired as 550 // a stable hazard ptr by the calling thread in a way that honored 551 // the Thread-SMR protocol. 552 // 553 // If the calling thread cannot be found by threads_do() and if 554 // it is not the shutdown thread, then the calling thread is not 555 // honoring the Thread-SMR ptotocol. This means that the specified 556 // ThreadsList is not a stable hazard ptr and can be freed by 557 // another thread from the to-be-deleted list at any time. 558 // 559 VerifyHazardPtrThreadClosure cl(_thread); 560 ThreadsSMRSupport::threads_do(&cl, _list); 561 562 // If the calling thread is not honoring the Thread-SMR protocol, 563 // then we will either crash in threads_do() above because 'threads' 564 // was freed by another thread or we will fail the assert() below. 565 // In either case, we won't get past this point with a badly placed 566 // ThreadsListHandle. 567 568 assert(cl.found(), "Acquired a ThreadsList snapshot from a thread not recognized by the Thread-SMR protocol."); 569 #endif 570 } 571 572 // 'entries + 1' so we always have at least one entry. 573 ThreadsList::ThreadsList(int entries) : 574 _length(entries), 575 _next_list(NULL), 576 _threads(NEW_C_HEAP_ARRAY(JavaThread*, entries + 1, mtThread)), 577 _nested_handle_cnt(0) 578 { 579 *(JavaThread**)(_threads + entries) = NULL; // Make sure the extra entry is NULL. 580 } 581 582 ThreadsList::~ThreadsList() { 583 FREE_C_HEAP_ARRAY(JavaThread*, _threads); 584 } 585 586 // Add a JavaThread to a ThreadsList. The returned ThreadsList is a 587 // new copy of the specified ThreadsList with the specified JavaThread 588 // appended to the end. 589 ThreadsList *ThreadsList::add_thread(ThreadsList *list, JavaThread *java_thread) { 590 const uint index = list->_length; 591 const uint new_length = index + 1; 592 const uint head_length = index; 593 ThreadsList *const new_list = new ThreadsList(new_length); 594 595 if (head_length > 0) { 596 Copy::disjoint_words((HeapWord*)list->_threads, (HeapWord*)new_list->_threads, head_length); 597 } 598 *(JavaThread**)(new_list->_threads + index) = java_thread; 599 600 return new_list; 601 } 602 603 void ThreadsList::dec_nested_handle_cnt() { 604 Atomic::dec(&_nested_handle_cnt); 605 } 606 607 int ThreadsList::find_index_of_JavaThread(JavaThread *target) { 608 if (target == NULL) { 609 return -1; 610 } 611 for (uint i = 0; i < length(); i++) { 612 if (target == thread_at(i)) { 613 return (int)i; 614 } 615 } 616 return -1; 617 } 618 619 JavaThread* ThreadsList::find_JavaThread_from_java_tid(jlong java_tid) const { 620 ThreadIdTable::lazy_initialize(this); 621 JavaThread* thread = ThreadIdTable::find_thread_by_tid(java_tid); 622 if (thread == NULL) { 623 // If the thread is not found in the table find it 624 // with a linear search and add to the table. 625 for (uint i = 0; i < length(); i++) { 626 thread = thread_at(i); 627 oop tobj = thread->threadObj(); 628 // Ignore the thread if it hasn't run yet, has exited 629 // or is starting to exit. 630 if (tobj != NULL && java_tid == java_lang_Thread::thread_id(tobj)) { 631 MutexLocker ml(Threads_lock); 632 // Must be inside the lock to ensure that we don't add a thread to the table 633 // that has just passed the removal point in ThreadsSMRSupport::remove_thread() 634 if (!thread->is_exiting()) { 635 ThreadIdTable::add_thread(java_tid, thread); 636 return thread; 637 } 638 } 639 } 640 } else if (!thread->is_exiting()) { 641 return thread; 642 } 643 return NULL; 644 } 645 646 void ThreadsList::inc_nested_handle_cnt() { 647 Atomic::inc(&_nested_handle_cnt); 648 } 649 650 bool ThreadsList::includes(const JavaThread * const p) const { 651 if (p == NULL) { 652 return false; 653 } 654 for (uint i = 0; i < length(); i++) { 655 if (thread_at(i) == p) { 656 return true; 657 } 658 } 659 return false; 660 } 661 662 // Remove a JavaThread from a ThreadsList. The returned ThreadsList is a 663 // new copy of the specified ThreadsList with the specified JavaThread 664 // removed. 665 ThreadsList *ThreadsList::remove_thread(ThreadsList* list, JavaThread* java_thread) { 666 assert(list->_length > 0, "sanity"); 667 668 uint i = (uint)list->find_index_of_JavaThread(java_thread); 669 assert(i < list->_length, "did not find JavaThread on the list"); 670 const uint index = i; 671 const uint new_length = list->_length - 1; 672 const uint head_length = index; 673 const uint tail_length = (new_length >= index) ? (new_length - index) : 0; 674 ThreadsList *const new_list = new ThreadsList(new_length); 675 676 if (head_length > 0) { 677 Copy::disjoint_words((HeapWord*)list->_threads, (HeapWord*)new_list->_threads, head_length); 678 } 679 if (tail_length > 0) { 680 Copy::disjoint_words((HeapWord*)list->_threads + index + 1, (HeapWord*)new_list->_threads + index, tail_length); 681 } 682 683 return new_list; 684 } 685 686 ThreadsListHandle::ThreadsListHandle(Thread *self) : _list_ptr(self, /* acquire */ true) { 687 assert(self == Thread::current(), "sanity check"); 688 if (EnableThreadSMRStatistics) { 689 _timer.start(); 690 } 691 } 692 693 ThreadsListHandle::~ThreadsListHandle() { 694 if (EnableThreadSMRStatistics) { 695 _timer.stop(); 696 uint millis = (uint)_timer.milliseconds(); 697 ThreadsSMRSupport::update_tlh_stats(millis); 698 } 699 } 700 701 // Convert an internal thread reference to a JavaThread found on the 702 // associated ThreadsList. This ThreadsListHandle "protects" the 703 // returned JavaThread *. 704 // 705 // If thread_oop_p is not NULL, then the caller wants to use the oop 706 // after this call so the oop is returned. On success, *jt_pp is set 707 // to the converted JavaThread * and true is returned. On error, 708 // returns false. 709 // 710 bool ThreadsListHandle::cv_internal_thread_to_JavaThread(jobject jthread, 711 JavaThread ** jt_pp, 712 oop * thread_oop_p) { 713 assert(this->list() != NULL, "must have a ThreadsList"); 714 assert(jt_pp != NULL, "must have a return JavaThread pointer"); 715 // thread_oop_p is optional so no assert() 716 717 // The JVM_* interfaces don't allow a NULL thread parameter; JVM/TI 718 // allows a NULL thread parameter to signify "current thread" which 719 // allows us to avoid calling cv_external_thread_to_JavaThread(). 720 // The JVM_* interfaces have no such leeway. 721 722 oop thread_oop = JNIHandles::resolve_non_null(jthread); 723 // Looks like an oop at this point. 724 if (thread_oop_p != NULL) { 725 // Return the oop to the caller; the caller may still want 726 // the oop even if this function returns false. 727 *thread_oop_p = thread_oop; 728 } 729 730 JavaThread *java_thread = java_lang_Thread::thread(thread_oop); 731 if (java_thread == NULL) { 732 // The java.lang.Thread does not contain a JavaThread * so it has 733 // not yet run or it has died. 734 return false; 735 } 736 // Looks like a live JavaThread at this point. 737 738 if (java_thread != JavaThread::current()) { 739 // jthread is not for the current JavaThread so have to verify 740 // the JavaThread * against the ThreadsList. 741 if (EnableThreadSMRExtraValidityChecks && !includes(java_thread)) { 742 // Not on the JavaThreads list so it is not alive. 743 return false; 744 } 745 } 746 747 // Return a live JavaThread that is "protected" by the 748 // ThreadsListHandle in the caller. 749 *jt_pp = java_thread; 750 return true; 751 } 752 753 void ThreadsSMRSupport::add_thread(JavaThread *thread){ 754 ThreadsList *new_list = ThreadsList::add_thread(get_java_thread_list(), thread); 755 if (EnableThreadSMRStatistics) { 756 inc_java_thread_list_alloc_cnt(); 757 update_java_thread_list_max(new_list->length()); 758 } 759 // Initial _java_thread_list will not generate a "Threads::add" mesg. 760 log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::add: new ThreadsList=" INTPTR_FORMAT, os::current_thread_id(), p2i(new_list)); 761 762 ThreadsList *old_list = xchg_java_thread_list(new_list); 763 free_list(old_list); 764 if (ThreadIdTable::is_initialized()) { 765 jlong tid = SharedRuntime::get_java_tid(thread); 766 ThreadIdTable::add_thread(tid, thread); 767 } 768 } 769 770 // set_delete_notify() and clear_delete_notify() are called 771 // under the protection of the delete_lock, but we also use an 772 // Atomic operation to ensure the memory update is seen earlier than 773 // when the delete_lock is dropped. 774 // 775 void ThreadsSMRSupport::clear_delete_notify() { 776 Atomic::dec(&_delete_notify); 777 } 778 779 bool ThreadsSMRSupport::delete_notify() { 780 // Use load_acquire() in order to see any updates to _delete_notify 781 // earlier than when delete_lock is grabbed. 782 return (Atomic::load_acquire(&_delete_notify) != 0); 783 } 784 785 // Safely free a ThreadsList after a Threads::add() or Threads::remove(). 786 // The specified ThreadsList may not get deleted during this call if it 787 // is still in-use (referenced by a hazard ptr). Other ThreadsLists 788 // in the chain may get deleted by this call if they are no longer in-use. 789 void ThreadsSMRSupport::free_list(ThreadsList* threads) { 790 assert_locked_or_safepoint(Threads_lock); 791 792 if (is_bootstrap_list(threads)) { 793 // The bootstrap list cannot be freed and is empty so 794 // it does not need to be scanned. Nothing to do here. 795 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)); 796 return; 797 } 798 799 threads->set_next_list(_to_delete_list); 800 _to_delete_list = threads; 801 if (EnableThreadSMRStatistics) { 802 _to_delete_list_cnt++; 803 if (_to_delete_list_cnt > _to_delete_list_max) { 804 _to_delete_list_max = _to_delete_list_cnt; 805 } 806 } 807 808 // Hash table size should be first power of two higher than twice the length of the ThreadsList 809 int hash_table_size = MIN2((int)get_java_thread_list()->length(), 32) << 1; 810 hash_table_size--; 811 hash_table_size |= hash_table_size >> 1; 812 hash_table_size |= hash_table_size >> 2; 813 hash_table_size |= hash_table_size >> 4; 814 hash_table_size |= hash_table_size >> 8; 815 hash_table_size |= hash_table_size >> 16; 816 hash_table_size++; 817 818 // Gather a hash table of the current hazard ptrs: 819 ThreadScanHashtable *scan_table = new ThreadScanHashtable(hash_table_size); 820 ScanHazardPtrGatherThreadsListClosure scan_cl(scan_table); 821 threads_do(&scan_cl); 822 OrderAccess::acquire(); // Must order reads of hazard ptr before reads of 823 // nested reference counters 824 825 // Walk through the linked list of pending freeable ThreadsLists 826 // and free the ones that are not referenced from hazard ptrs. 827 ThreadsList* current = _to_delete_list; 828 ThreadsList* prev = NULL; 829 ThreadsList* next = NULL; 830 bool threads_is_freed = false; 831 while (current != NULL) { 832 next = current->next_list(); 833 if (!scan_table->has_entry((void*)current) && current->_nested_handle_cnt == 0) { 834 // This ThreadsList is not referenced by a hazard ptr. 835 if (prev != NULL) { 836 prev->set_next_list(next); 837 } 838 if (_to_delete_list == current) { 839 _to_delete_list = next; 840 } 841 842 log_debug(thread, smr)("tid=" UINTX_FORMAT ": ThreadsSMRSupport::free_list: threads=" INTPTR_FORMAT " is freed.", os::current_thread_id(), p2i(current)); 843 if (current == threads) threads_is_freed = true; 844 delete current; 845 if (EnableThreadSMRStatistics) { 846 _java_thread_list_free_cnt++; 847 _to_delete_list_cnt--; 848 } 849 } else { 850 prev = current; 851 } 852 current = next; 853 } 854 855 if (!threads_is_freed) { 856 // Only report "is not freed" on the original call to 857 // free_list() for this ThreadsList. 858 log_debug(thread, smr)("tid=" UINTX_FORMAT ": ThreadsSMRSupport::free_list: threads=" INTPTR_FORMAT " is not freed.", os::current_thread_id(), p2i(threads)); 859 } 860 861 delete scan_table; 862 } 863 864 // Return true if the specified JavaThread is protected by a hazard 865 // pointer (ThreadsList reference). Otherwise, returns false. 866 // 867 bool ThreadsSMRSupport::is_a_protected_JavaThread(JavaThread *thread) { 868 assert_locked_or_safepoint(Threads_lock); 869 870 // Hash table size should be first power of two higher than twice 871 // the length of the Threads list. 872 int hash_table_size = MIN2((int)get_java_thread_list()->length(), 32) << 1; 873 hash_table_size--; 874 hash_table_size |= hash_table_size >> 1; 875 hash_table_size |= hash_table_size >> 2; 876 hash_table_size |= hash_table_size >> 4; 877 hash_table_size |= hash_table_size >> 8; 878 hash_table_size |= hash_table_size >> 16; 879 hash_table_size++; 880 881 // Gather a hash table of the JavaThreads indirectly referenced by 882 // hazard ptrs. 883 ThreadScanHashtable *scan_table = new ThreadScanHashtable(hash_table_size); 884 ScanHazardPtrGatherProtectedThreadsClosure scan_cl(scan_table); 885 threads_do(&scan_cl); 886 OrderAccess::acquire(); // Must order reads of hazard ptr before reads of 887 // nested reference counters 888 889 // Walk through the linked list of pending freeable ThreadsLists 890 // and include the ones that are currently in use by a nested 891 // ThreadsListHandle in the search set. 892 ThreadsList* current = _to_delete_list; 893 while (current != NULL) { 894 if (current->_nested_handle_cnt != 0) { 895 // 'current' is in use by a nested ThreadsListHandle so the hazard 896 // ptr is protecting all the JavaThreads on that ThreadsList. 897 AddThreadHazardPointerThreadClosure add_cl(scan_table); 898 current->threads_do(&add_cl); 899 } 900 current = current->next_list(); 901 } 902 903 bool thread_is_protected = false; 904 if (scan_table->has_entry((void*)thread)) { 905 thread_is_protected = true; 906 } 907 delete scan_table; 908 return thread_is_protected; 909 } 910 911 // Wake up portion of the release stable ThreadsList protocol; 912 // uses the delete_lock(). 913 // 914 void ThreadsSMRSupport::release_stable_list_wake_up(bool is_nested) { 915 const char* log_str = is_nested ? "nested hazard ptr" : "regular hazard ptr"; 916 917 // Note: delete_lock is held in smr_delete() for the entire 918 // hazard ptr search so that we do not lose this notify() if 919 // the exiting thread has to wait. That code path also holds 920 // Threads_lock (which was grabbed before delete_lock) so that 921 // threads_do() can be called. This means the system can't start a 922 // safepoint which means this thread can't take too long to get to 923 // a safepoint because of being blocked on delete_lock. 924 // 925 MonitorLocker ml(ThreadsSMRSupport::delete_lock(), Monitor::_no_safepoint_check_flag); 926 if (ThreadsSMRSupport::delete_notify()) { 927 // Notify any exiting JavaThreads that are waiting in smr_delete() 928 // that we've released a ThreadsList. 929 ml.notify_all(); 930 log_debug(thread, smr)("tid=" UINTX_FORMAT ": ThreadsSMRSupport::release_stable_list notified %s", os::current_thread_id(), log_str); 931 } 932 } 933 934 void ThreadsSMRSupport::remove_thread(JavaThread *thread) { 935 if (ThreadIdTable::is_initialized()) { 936 jlong tid = SharedRuntime::get_java_tid(thread); 937 ThreadIdTable::remove_thread(tid); 938 } 939 ThreadsList *new_list = ThreadsList::remove_thread(ThreadsSMRSupport::get_java_thread_list(), thread); 940 if (EnableThreadSMRStatistics) { 941 ThreadsSMRSupport::inc_java_thread_list_alloc_cnt(); 942 // This list is smaller so no need to check for a "longest" update. 943 } 944 945 // Final _java_thread_list will not generate a "Threads::remove" mesg. 946 log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::remove: new ThreadsList=" INTPTR_FORMAT, os::current_thread_id(), p2i(new_list)); 947 948 ThreadsList *old_list = ThreadsSMRSupport::xchg_java_thread_list(new_list); 949 ThreadsSMRSupport::free_list(old_list); 950 } 951 952 // See note for clear_delete_notify(). 953 // 954 void ThreadsSMRSupport::set_delete_notify() { 955 Atomic::inc(&_delete_notify); 956 } 957 958 // Safely delete a JavaThread when it is no longer in use by a 959 // ThreadsListHandle. 960 // 961 void ThreadsSMRSupport::smr_delete(JavaThread *thread) { 962 assert(!Threads_lock->owned_by_self(), "sanity"); 963 964 bool has_logged_once = false; 965 elapsedTimer timer; 966 if (EnableThreadSMRStatistics) { 967 timer.start(); 968 } 969 970 while (true) { 971 { 972 // Will not make a safepoint check because this JavaThread 973 // is not on the current ThreadsList. 974 MutexLocker ml(Threads_lock); 975 // Cannot use a MonitorLocker helper here because we have 976 // to drop the Threads_lock first if we wait. 977 ThreadsSMRSupport::delete_lock()->lock_without_safepoint_check(); 978 // Set the delete_notify flag after we grab delete_lock 979 // and before we scan hazard ptrs because we're doing 980 // double-check locking in release_stable_list(). 981 ThreadsSMRSupport::set_delete_notify(); 982 983 if (!is_a_protected_JavaThread(thread)) { 984 // This is the common case. 985 ThreadsSMRSupport::clear_delete_notify(); 986 ThreadsSMRSupport::delete_lock()->unlock(); 987 break; 988 } 989 if (!has_logged_once) { 990 has_logged_once = true; 991 log_debug(thread, smr)("tid=" UINTX_FORMAT ": ThreadsSMRSupport::smr_delete: thread=" INTPTR_FORMAT " is not deleted.", os::current_thread_id(), p2i(thread)); 992 if (log_is_enabled(Debug, os, thread)) { 993 ScanHazardPtrPrintMatchingThreadsClosure scan_cl(thread); 994 threads_do(&scan_cl); 995 ThreadsList* current = _to_delete_list; 996 while (current != NULL) { 997 if (current->_nested_handle_cnt != 0 && current->includes(thread)) { 998 log_debug(thread, smr)("tid=" UINTX_FORMAT ": ThreadsSMRSupport::smr_delete: found nested hazard pointer to thread=" INTPTR_FORMAT, os::current_thread_id(), p2i(thread)); 999 } 1000 current = current->next_list(); 1001 } 1002 } 1003 } 1004 } // We have to drop the Threads_lock to wait or delete the thread 1005 1006 if (EnableThreadSMRStatistics) { 1007 _delete_lock_wait_cnt++; 1008 if (_delete_lock_wait_cnt > _delete_lock_wait_max) { 1009 _delete_lock_wait_max = _delete_lock_wait_cnt; 1010 } 1011 } 1012 // Wait for a release_stable_list() call before we check again. No 1013 // safepoint check, no timeout, and not as suspend equivalent flag 1014 // because this JavaThread is not on the Threads list. 1015 ThreadsSMRSupport::delete_lock()->wait_without_safepoint_check(); 1016 if (EnableThreadSMRStatistics) { 1017 _delete_lock_wait_cnt--; 1018 } 1019 1020 ThreadsSMRSupport::clear_delete_notify(); 1021 ThreadsSMRSupport::delete_lock()->unlock(); 1022 // Retry the whole scenario. 1023 } 1024 1025 delete thread; 1026 if (EnableThreadSMRStatistics) { 1027 timer.stop(); 1028 uint millis = (uint)timer.milliseconds(); 1029 ThreadsSMRSupport::inc_deleted_thread_cnt(); 1030 ThreadsSMRSupport::add_deleted_thread_times(millis); 1031 ThreadsSMRSupport::update_deleted_thread_time_max(millis); 1032 } 1033 1034 log_debug(thread, smr)("tid=" UINTX_FORMAT ": ThreadsSMRSupport::smr_delete: thread=" INTPTR_FORMAT " is deleted.", os::current_thread_id(), p2i(thread)); 1035 } 1036 1037 // Apply the closure to all threads in the system, with a snapshot of 1038 // all JavaThreads provided by the list parameter. 1039 void ThreadsSMRSupport::threads_do(ThreadClosure *tc, ThreadsList *list) { 1040 list->threads_do(tc); 1041 Threads::non_java_threads_do(tc); 1042 } 1043 1044 // Apply the closure to all threads in the system. 1045 void ThreadsSMRSupport::threads_do(ThreadClosure *tc) { 1046 threads_do(tc, _java_thread_list); 1047 } 1048 1049 1050 // Debug, logging, and printing stuff at the end: 1051 1052 // Print SMR info for a SafeThreadsListPtr to a given output stream. 1053 void SafeThreadsListPtr::print_on(outputStream* st) { 1054 if (this == _thread->_threads_list_ptr) { 1055 // The top level hazard ptr. 1056 st->print(" _threads_hazard_ptr=" INTPTR_FORMAT, p2i(_list)); 1057 } else { 1058 // Nested hazard ptrs. 1059 st->print(", _nested_threads_hazard_ptr=" INTPTR_FORMAT, p2i(_list)); 1060 } 1061 } 1062 1063 // Log Threads class SMR info. 1064 void ThreadsSMRSupport::log_statistics() { 1065 LogTarget(Info, thread, smr) log; 1066 if (log.is_enabled()) { 1067 LogStream out(log); 1068 print_info_on(&out); 1069 } 1070 } 1071 1072 // Print SMR info for a thread to a given output stream. 1073 void ThreadsSMRSupport::print_info_on(const Thread* thread, outputStream* st) { 1074 if (thread->_threads_hazard_ptr != NULL) { 1075 st->print(" _threads_hazard_ptr=" INTPTR_FORMAT, p2i(thread->_threads_hazard_ptr)); 1076 } 1077 if (EnableThreadSMRStatistics && thread->_threads_list_ptr != NULL) { 1078 // The count is only interesting if we have a _threads_list_ptr. 1079 st->print(", _nested_threads_hazard_ptr_cnt=%u", thread->_nested_threads_hazard_ptr_cnt); 1080 } 1081 if (SafepointSynchronize::is_at_safepoint() || Thread::current() == thread) { 1082 // It is only safe to walk the list if we're at a safepoint or the 1083 // calling thread is walking its own list. 1084 SafeThreadsListPtr* current = thread->_threads_list_ptr; 1085 if (current != NULL) { 1086 // Skip the top nesting level as it is always printed above. 1087 current = current->previous(); 1088 } 1089 while (current != NULL) { 1090 current->print_on(st); 1091 current = current->previous(); 1092 } 1093 } 1094 } 1095 1096 // Print Threads class SMR info. 1097 void ThreadsSMRSupport::print_info_on(outputStream* st) { 1098 // Only grab the Threads_lock if we don't already own it and if we 1099 // are not reporting an error. 1100 // Note: Not grabbing the Threads_lock during error reporting is 1101 // dangerous because the data structures we want to print can be 1102 // freed concurrently. However, grabbing the Threads_lock during 1103 // error reporting can be equally dangerous since this thread might 1104 // block during error reporting or a nested error could leave the 1105 // Threads_lock held. The classic no win scenario. 1106 // 1107 MutexLocker ml((Threads_lock->owned_by_self() || VMError::is_error_reported()) ? NULL : Threads_lock); 1108 1109 st->print_cr("Threads class SMR info:"); 1110 st->print_cr("_java_thread_list=" INTPTR_FORMAT ", length=%u, " 1111 "elements={", p2i(_java_thread_list), 1112 _java_thread_list->length()); 1113 print_info_elements_on(st, _java_thread_list); 1114 st->print_cr("}"); 1115 if (_to_delete_list != NULL) { 1116 st->print_cr("_to_delete_list=" INTPTR_FORMAT ", length=%u, " 1117 "elements={", p2i(_to_delete_list), 1118 _to_delete_list->length()); 1119 print_info_elements_on(st, _to_delete_list); 1120 st->print_cr("}"); 1121 for (ThreadsList *t_list = _to_delete_list->next_list(); 1122 t_list != NULL; t_list = t_list->next_list()) { 1123 st->print("next-> " INTPTR_FORMAT ", length=%u, " 1124 "elements={", p2i(t_list), t_list->length()); 1125 print_info_elements_on(st, t_list); 1126 st->print_cr("}"); 1127 } 1128 } 1129 if (!EnableThreadSMRStatistics) { 1130 return; 1131 } 1132 st->print_cr("_java_thread_list_alloc_cnt=" UINT64_FORMAT ", " 1133 "_java_thread_list_free_cnt=" UINT64_FORMAT ", " 1134 "_java_thread_list_max=%u, " 1135 "_nested_thread_list_max=%u", 1136 _java_thread_list_alloc_cnt, 1137 _java_thread_list_free_cnt, 1138 _java_thread_list_max, 1139 _nested_thread_list_max); 1140 if (_tlh_cnt > 0) { 1141 st->print_cr("_tlh_cnt=%u" 1142 ", _tlh_times=%u" 1143 ", avg_tlh_time=%0.2f" 1144 ", _tlh_time_max=%u", 1145 _tlh_cnt, _tlh_times, 1146 ((double) _tlh_times / _tlh_cnt), 1147 _tlh_time_max); 1148 } 1149 if (_deleted_thread_cnt > 0) { 1150 st->print_cr("_deleted_thread_cnt=%u" 1151 ", _deleted_thread_times=%u" 1152 ", avg_deleted_thread_time=%0.2f" 1153 ", _deleted_thread_time_max=%u", 1154 _deleted_thread_cnt, _deleted_thread_times, 1155 ((double) _deleted_thread_times / _deleted_thread_cnt), 1156 _deleted_thread_time_max); 1157 } 1158 st->print_cr("_delete_lock_wait_cnt=%u, _delete_lock_wait_max=%u", 1159 _delete_lock_wait_cnt, _delete_lock_wait_max); 1160 st->print_cr("_to_delete_list_cnt=%u, _to_delete_list_max=%u", 1161 _to_delete_list_cnt, _to_delete_list_max); 1162 } 1163 1164 // Print ThreadsList elements (4 per line). 1165 void ThreadsSMRSupport::print_info_elements_on(outputStream* st, ThreadsList* t_list) { 1166 uint cnt = 0; 1167 JavaThreadIterator jti(t_list); 1168 for (JavaThread *jt = jti.first(); jt != NULL; jt = jti.next()) { 1169 st->print(INTPTR_FORMAT, p2i(jt)); 1170 if (cnt < t_list->length() - 1) { 1171 // Separate with comma or comma-space except for the last one. 1172 if (((cnt + 1) % 4) == 0) { 1173 // Four INTPTR_FORMAT fit on an 80 column line so end the 1174 // current line with just a comma. 1175 st->print_cr(","); 1176 } else { 1177 // Not the last one on the current line so use comma-space: 1178 st->print(", "); 1179 } 1180 } else { 1181 // Last one so just end the current line. 1182 st->cr(); 1183 } 1184 cnt++; 1185 } 1186 }