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