1 /*
2 * Copyright (c) 2001, 2015, 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 "memory/allocation.hpp"
27 #include "memory/allocation.inline.hpp"
28 #include "runtime/atomic.inline.hpp"
29 #include "runtime/os.hpp"
30 #include "utilities/workgroup.hpp"
31
32 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
33
34 // Definitions of WorkGang methods.
35
36 AbstractWorkGang::AbstractWorkGang(const char* name,
37 bool are_GC_task_threads,
38 bool are_ConcurrentGC_threads) :
39 _name(name),
40 _are_GC_task_threads(are_GC_task_threads),
41 _are_ConcurrentGC_threads(are_ConcurrentGC_threads) {
42
43 assert(!(are_GC_task_threads && are_ConcurrentGC_threads),
44 "They cannot both be STW GC and Concurrent threads" );
45
46 // Other initialization.
47 _monitor = new Monitor(/* priority */ Mutex::leaf,
48 /* name */ "WorkGroup monitor",
49 /* allow_vm_block */ are_GC_task_threads,
50 Monitor::_safepoint_check_sometimes);
51 assert(monitor() != NULL, "Failed to allocate monitor");
52 _terminate = false;
53 _task = NULL;
54 _sequence_number = 0;
55 _started_workers = 0;
56 _finished_workers = 0;
57 }
58
59 WorkGang::WorkGang(const char* name,
60 uint workers,
61 bool are_GC_task_threads,
62 bool are_ConcurrentGC_threads) :
63 AbstractWorkGang(name, are_GC_task_threads, are_ConcurrentGC_threads) {
64 _total_workers = workers;
65 }
66
67 GangWorker* WorkGang::allocate_worker(uint which) {
68 GangWorker* new_worker = new GangWorker(this, which);
69 return new_worker;
70 }
71
72 // The current implementation will exit if the allocation
73 // of any worker fails. Still, return a boolean so that
74 // a future implementation can possibly do a partial
75 // initialization of the workers and report such to the
76 // caller.
77 bool WorkGang::initialize_workers() {
78
79 if (TraceWorkGang) {
80 tty->print_cr("Constructing work gang %s with %d threads",
81 name(),
82 total_workers());
83 }
84 _gang_workers = NEW_C_HEAP_ARRAY(GangWorker*, total_workers(), mtInternal);
85 if (gang_workers() == NULL) {
86 vm_exit_out_of_memory(0, OOM_MALLOC_ERROR, "Cannot create GangWorker array.");
87 return false;
88 }
89 os::ThreadType worker_type;
90 if (are_ConcurrentGC_threads()) {
91 worker_type = os::cgc_thread;
92 } else {
93 worker_type = os::pgc_thread;
94 }
95 for (uint worker = 0; worker < total_workers(); worker += 1) {
96 GangWorker* new_worker = allocate_worker(worker);
97 assert(new_worker != NULL, "Failed to allocate GangWorker");
98 _gang_workers[worker] = new_worker;
99 if (new_worker == NULL || !os::create_thread(new_worker, worker_type)) {
100 vm_exit_out_of_memory(0, OOM_MALLOC_ERROR,
101 "Cannot create worker GC thread. Out of system resources.");
102 return false;
103 }
104 if (!DisableStartThread) {
105 os::start_thread(new_worker);
106 }
107 }
108 return true;
109 }
110
111 AbstractWorkGang::~AbstractWorkGang() {
112 if (TraceWorkGang) {
113 tty->print_cr("Destructing work gang %s", name());
114 }
115 stop(); // stop all the workers
116 for (uint worker = 0; worker < total_workers(); worker += 1) {
117 delete gang_worker(worker);
118 }
119 delete gang_workers();
120 delete monitor();
121 }
122
123 GangWorker* AbstractWorkGang::gang_worker(uint i) const {
124 // Array index bounds checking.
125 GangWorker* result = NULL;
126 assert(gang_workers() != NULL, "No workers for indexing");
127 assert(i < total_workers(), "Worker index out of bounds");
128 result = _gang_workers[i];
129 assert(result != NULL, "Indexing to null worker");
130 return result;
131 }
132
133 void WorkGang::run_task(AbstractGangTask* task) {
134 run_task(task, total_workers());
135 }
136
137 void WorkGang::run_task(AbstractGangTask* task, uint no_of_parallel_workers) {
138 task->set_for_termination(no_of_parallel_workers);
139
140 // This thread is executed by the VM thread which does not block
141 // on ordinary MutexLocker's.
142 MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag);
143 if (TraceWorkGang) {
144 tty->print_cr("Running work gang %s task %s", name(), task->name());
145 }
146 // Tell all the workers to run a task.
147 assert(task != NULL, "Running a null task");
148 // Initialize.
149 _task = task;
150 _sequence_number += 1;
151 _started_workers = 0;
152 _finished_workers = 0;
153 // Tell the workers to get to work.
154 monitor()->notify_all();
155 // Wait for them to be finished
156 while (finished_workers() < no_of_parallel_workers) {
157 if (TraceWorkGang) {
158 tty->print_cr("Waiting in work gang %s: %d/%d finished sequence %d",
159 name(), finished_workers(), no_of_parallel_workers,
160 _sequence_number);
161 }
162 monitor()->wait(/* no_safepoint_check */ true);
163 }
164 _task = NULL;
165 if (TraceWorkGang) {
166 tty->print_cr("\nFinished work gang %s: %d/%d sequence %d",
167 name(), finished_workers(), no_of_parallel_workers,
168 _sequence_number);
169 Thread* me = Thread::current();
170 tty->print_cr(" T: 0x%x VM_thread: %d", me, me->is_VM_thread());
171 }
172 }
173
174 void FlexibleWorkGang::run_task(AbstractGangTask* task) {
175 // If active_workers() is passed, _finished_workers
176 // must only be incremented for workers that find non_null
177 // work (as opposed to all those that just check that the
178 // task is not null).
179 WorkGang::run_task(task, (uint) active_workers());
180 }
181
182 void AbstractWorkGang::stop() {
183 // Tell all workers to terminate, then wait for them to become inactive.
184 MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag);
185 if (TraceWorkGang) {
186 tty->print_cr("Stopping work gang %s task %s", name(), task()->name());
187 }
188 _task = NULL;
189 _terminate = true;
190 monitor()->notify_all();
191 while (finished_workers() < active_workers()) {
192 if (TraceWorkGang) {
193 tty->print_cr("Waiting in work gang %s: %d/%d finished",
194 name(), finished_workers(), active_workers());
195 }
196 monitor()->wait(/* no_safepoint_check */ true);
197 }
198 }
199
200 void AbstractWorkGang::internal_worker_poll(WorkData* data) const {
201 assert(monitor()->owned_by_self(), "worker_poll is an internal method");
202 assert(data != NULL, "worker data is null");
203 data->set_terminate(terminate());
204 data->set_task(task());
205 data->set_sequence_number(sequence_number());
206 }
207
208 void AbstractWorkGang::internal_note_start() {
209 assert(monitor()->owned_by_self(), "note_finish is an internal method");
210 _started_workers += 1;
211 }
212
213 void AbstractWorkGang::internal_note_finish() {
214 assert(monitor()->owned_by_self(), "note_finish is an internal method");
215 _finished_workers += 1;
216 }
217
218 void AbstractWorkGang::print_worker_threads_on(outputStream* st) const {
219 uint num_thr = total_workers();
220 for (uint i = 0; i < num_thr; i++) {
221 gang_worker(i)->print_on(st);
222 st->cr();
223 }
224 }
225
226 void AbstractWorkGang::threads_do(ThreadClosure* tc) const {
227 assert(tc != NULL, "Null ThreadClosure");
228 uint num_thr = total_workers();
229 for (uint i = 0; i < num_thr; i++) {
230 tc->do_thread(gang_worker(i));
231 }
232 }
233
234 // GangWorker methods.
235
236 GangWorker::GangWorker(AbstractWorkGang* gang, uint id) {
237 _gang = gang;
238 set_id(id);
239 set_name("%s#%d", gang->name(), id);
240 }
241
242 void GangWorker::run() {
243 initialize();
244 loop();
245 }
246
247 void GangWorker::initialize() {
248 this->initialize_thread_local_storage();
249 this->record_stack_base_and_size();
250 this->initialize_named_thread();
251 assert(_gang != NULL, "No gang to run in");
252 os::set_priority(this, NearMaxPriority);
253 if (TraceWorkGang) {
254 tty->print_cr("Running gang worker for gang %s id %d",
255 gang()->name(), id());
256 }
257 // The VM thread should not execute here because MutexLocker's are used
258 // as (opposed to MutexLockerEx's).
259 assert(!Thread::current()->is_VM_thread(), "VM thread should not be part"
260 " of a work gang");
261 }
262
263 void GangWorker::loop() {
264 int previous_sequence_number = 0;
265 Monitor* gang_monitor = gang()->monitor();
266 for ( ; /* !terminate() */; ) {
267 WorkData data;
268 int part; // Initialized below.
269 {
270 // Grab the gang mutex.
271 MutexLocker ml(gang_monitor);
272 // Wait for something to do.
273 // Polling outside the while { wait } avoids missed notifies
274 // in the outer loop.
275 gang()->internal_worker_poll(&data);
276 if (TraceWorkGang) {
277 tty->print("Polled outside for work in gang %s worker %d",
278 gang()->name(), id());
279 tty->print(" terminate: %s",
280 data.terminate() ? "true" : "false");
281 tty->print(" sequence: %d (prev: %d)",
282 data.sequence_number(), previous_sequence_number);
283 if (data.task() != NULL) {
284 tty->print(" task: %s", data.task()->name());
285 } else {
286 tty->print(" task: NULL");
287 }
288 tty->cr();
289 }
290 for ( ; /* break or return */; ) {
291 // Terminate if requested.
292 if (data.terminate()) {
293 gang()->internal_note_finish();
294 gang_monitor->notify_all();
295 return;
296 }
297 // Check for new work.
298 if ((data.task() != NULL) &&
299 (data.sequence_number() != previous_sequence_number)) {
300 if (gang()->needs_more_workers()) {
301 gang()->internal_note_start();
302 gang_monitor->notify_all();
303 part = gang()->started_workers() - 1;
304 break;
305 }
306 }
307 // Nothing to do.
308 gang_monitor->wait(/* no_safepoint_check */ true);
309 gang()->internal_worker_poll(&data);
310 if (TraceWorkGang) {
311 tty->print("Polled inside for work in gang %s worker %d",
312 gang()->name(), id());
313 tty->print(" terminate: %s",
314 data.terminate() ? "true" : "false");
315 tty->print(" sequence: %d (prev: %d)",
316 data.sequence_number(), previous_sequence_number);
317 if (data.task() != NULL) {
318 tty->print(" task: %s", data.task()->name());
319 } else {
320 tty->print(" task: NULL");
321 }
322 tty->cr();
323 }
324 }
325 // Drop gang mutex.
326 }
327 if (TraceWorkGang) {
328 tty->print("Work for work gang %s id %d task %s part %d",
329 gang()->name(), id(), data.task()->name(), part);
330 }
331 assert(data.task() != NULL, "Got null task");
332 data.task()->work(part);
333 {
334 if (TraceWorkGang) {
335 tty->print("Finish for work gang %s id %d task %s part %d",
336 gang()->name(), id(), data.task()->name(), part);
337 }
338 // Grab the gang mutex.
339 MutexLocker ml(gang_monitor);
340 gang()->internal_note_finish();
341 // Tell the gang you are done.
342 gang_monitor->notify_all();
343 // Drop the gang mutex.
344 }
345 previous_sequence_number = data.sequence_number();
346 }
347 }
348
349 bool GangWorker::is_GC_task_thread() const {
350 return gang()->are_GC_task_threads();
351 }
352
353 bool GangWorker::is_ConcurrentGC_thread() const {
354 return gang()->are_ConcurrentGC_threads();
355 }
356
357 void GangWorker::print_on(outputStream* st) const {
358 st->print("\"%s\" ", name());
359 Thread::print_on(st);
360 st->cr();
361 }
362
363 // Printing methods
364
365 const char* AbstractWorkGang::name() const {
366 return _name;
367 }
368
369 #ifndef PRODUCT
370
371 const char* AbstractGangTask::name() const {
372 return _name;
373 }
374
375 #endif /* PRODUCT */
376
377 // FlexibleWorkGang
378
379
380 // *** WorkGangBarrierSync
381
382 WorkGangBarrierSync::WorkGangBarrierSync()
383 : _monitor(Mutex::safepoint, "work gang barrier sync", true,
384 Monitor::_safepoint_check_never),
385 _n_workers(0), _n_completed(0), _should_reset(false), _aborted(false) {
386 }
387
388 WorkGangBarrierSync::WorkGangBarrierSync(uint n_workers, const char* name)
389 : _monitor(Mutex::safepoint, name, true, Monitor::_safepoint_check_never),
390 _n_workers(n_workers), _n_completed(0), _should_reset(false), _aborted(false) {
391 }
392
393 void WorkGangBarrierSync::set_n_workers(uint n_workers) {
394 _n_workers = n_workers;
395 _n_completed = 0;
396 _should_reset = false;
397 _aborted = false;
398 }
399
400 bool WorkGangBarrierSync::enter() {
401 MutexLockerEx x(monitor(), Mutex::_no_safepoint_check_flag);
402 if (should_reset()) {
403 // The should_reset() was set and we are the first worker to enter
404 // the sync barrier. We will zero the n_completed() count which
405 // effectively resets the barrier.
406 zero_completed();
407 set_should_reset(false);
408 }
409 inc_completed();
410 if (n_completed() == n_workers()) {
411 // At this point we would like to reset the barrier to be ready in
412 // case it is used again. However, we cannot set n_completed() to
413 // 0, even after the notify_all(), given that some other workers
414 // might still be waiting for n_completed() to become ==
415 // n_workers(). So, if we set n_completed() to 0, those workers
416 // will get stuck (as they will wake up, see that n_completed() !=
417 // n_workers() and go back to sleep). Instead, we raise the
418 // should_reset() flag and the barrier will be reset the first
419 // time a worker enters it again.
420 set_should_reset(true);
421 monitor()->notify_all();
422 } else {
423 while (n_completed() != n_workers() && !aborted()) {
424 monitor()->wait(/* no_safepoint_check */ true);
425 }
426 }
427 return !aborted();
428 }
429
430 void WorkGangBarrierSync::abort() {
431 MutexLockerEx x(monitor(), Mutex::_no_safepoint_check_flag);
432 set_aborted();
433 monitor()->notify_all();
434 }
435
436 // SubTasksDone functions.
437
438 SubTasksDone::SubTasksDone(uint n) :
439 _n_tasks(n), _n_threads(1), _tasks(NULL) {
440 _tasks = NEW_C_HEAP_ARRAY(uint, n, mtInternal);
441 guarantee(_tasks != NULL, "alloc failure");
442 clear();
443 }
444
445 bool SubTasksDone::valid() {
446 return _tasks != NULL;
447 }
448
449 void SubTasksDone::set_n_threads(uint t) {
450 assert(_claimed == 0 || _threads_completed == _n_threads,
451 "should not be called while tasks are being processed!");
452 _n_threads = (t == 0 ? 1 : t);
453 }
454
455 void SubTasksDone::clear() {
456 for (uint i = 0; i < _n_tasks; i++) {
457 _tasks[i] = 0;
458 }
459 _threads_completed = 0;
460 #ifdef ASSERT
461 _claimed = 0;
462 #endif
463 }
464
465 bool SubTasksDone::is_task_claimed(uint t) {
466 assert(t < _n_tasks, "bad task id.");
467 uint old = _tasks[t];
468 if (old == 0) {
469 old = Atomic::cmpxchg(1, &_tasks[t], 0);
470 }
471 assert(_tasks[t] == 1, "What else?");
472 bool res = old != 0;
473 #ifdef ASSERT
474 if (!res) {
475 assert(_claimed < _n_tasks, "Too many tasks claimed; missing clear?");
476 Atomic::inc((volatile jint*) &_claimed);
477 }
478 #endif
479 return res;
480 }
481
482 void SubTasksDone::all_tasks_completed() {
483 jint observed = _threads_completed;
484 jint old;
485 do {
486 old = observed;
487 observed = Atomic::cmpxchg(old+1, &_threads_completed, old);
488 } while (observed != old);
489 // If this was the last thread checking in, clear the tasks.
490 if (observed+1 == (jint)_n_threads) clear();
491 }
492
493
494 SubTasksDone::~SubTasksDone() {
495 if (_tasks != NULL) FREE_C_HEAP_ARRAY(jint, _tasks);
496 }
497
498 // *** SequentialSubTasksDone
499
500 void SequentialSubTasksDone::clear() {
501 _n_tasks = _n_claimed = 0;
502 _n_threads = _n_completed = 0;
503 }
504
505 bool SequentialSubTasksDone::valid() {
506 return _n_threads > 0;
507 }
508
509 bool SequentialSubTasksDone::is_task_claimed(uint& t) {
510 uint* n_claimed_ptr = &_n_claimed;
511 t = *n_claimed_ptr;
512 while (t < _n_tasks) {
513 jint res = Atomic::cmpxchg(t+1, n_claimed_ptr, t);
514 if (res == (jint)t) {
515 return false;
516 }
517 t = *n_claimed_ptr;
518 }
519 return true;
520 }
521
522 bool SequentialSubTasksDone::all_tasks_completed() {
523 uint* n_completed_ptr = &_n_completed;
524 uint complete = *n_completed_ptr;
525 while (true) {
526 uint res = Atomic::cmpxchg(complete+1, n_completed_ptr, complete);
527 if (res == complete) {
528 break;
529 }
530 complete = res;
531 }
532 if (complete+1 == _n_threads) {
533 clear();
534 return true;
535 }
536 return false;
537 }
538
539 bool FreeIdSet::_stat_init = false;
540 FreeIdSet* FreeIdSet::_sets[NSets];
541 bool FreeIdSet::_safepoint;
542
543 FreeIdSet::FreeIdSet(int sz, Monitor* mon) :
544 _sz(sz), _mon(mon), _hd(0), _waiters(0), _index(-1), _claimed(0)
545 {
546 _ids = NEW_C_HEAP_ARRAY(int, sz, mtInternal);
547 for (int i = 0; i < sz; i++) _ids[i] = i+1;
548 _ids[sz-1] = end_of_list; // end of list.
549 if (_stat_init) {
550 for (int j = 0; j < NSets; j++) _sets[j] = NULL;
551 _stat_init = true;
552 }
553 // Add to sets. (This should happen while the system is still single-threaded.)
554 for (int j = 0; j < NSets; j++) {
555 if (_sets[j] == NULL) {
556 _sets[j] = this;
557 _index = j;
558 break;
559 }
560 }
561 guarantee(_index != -1, "Too many FreeIdSets in use!");
562 }
563
564 FreeIdSet::~FreeIdSet() {
565 _sets[_index] = NULL;
566 FREE_C_HEAP_ARRAY(int, _ids);
567 }
568
569 void FreeIdSet::set_safepoint(bool b) {
570 _safepoint = b;
571 if (b) {
572 for (int j = 0; j < NSets; j++) {
573 if (_sets[j] != NULL && _sets[j]->_waiters > 0) {
574 Monitor* mon = _sets[j]->_mon;
575 mon->lock_without_safepoint_check();
576 mon->notify_all();
577 mon->unlock();
578 }
579 }
580 }
581 }
582
583 #define FID_STATS 0
584
585 int FreeIdSet::claim_par_id() {
586 #if FID_STATS
587 thread_t tslf = thr_self();
588 tty->print("claim_par_id[%d]: sz = %d, claimed = %d\n", tslf, _sz, _claimed);
589 #endif
590 MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);
591 while (!_safepoint && _hd == end_of_list) {
592 _waiters++;
593 #if FID_STATS
594 if (_waiters > 5) {
595 tty->print("claim_par_id waiting[%d]: %d waiters, %d claimed.\n",
596 tslf, _waiters, _claimed);
597 }
598 #endif
599 _mon->wait(Mutex::_no_safepoint_check_flag);
600 _waiters--;
601 }
602 if (_hd == end_of_list) {
603 #if FID_STATS
604 tty->print("claim_par_id[%d]: returning EOL.\n", tslf);
605 #endif
606 return -1;
607 } else {
608 int res = _hd;
609 _hd = _ids[res];
610 _ids[res] = claimed; // For debugging.
611 _claimed++;
612 #if FID_STATS
613 tty->print("claim_par_id[%d]: returning %d, claimed = %d.\n",
614 tslf, res, _claimed);
615 #endif
616 return res;
617 }
618 }
619
620 bool FreeIdSet::claim_perm_id(int i) {
621 assert(0 <= i && i < _sz, "Out of range.");
622 MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);
623 int prev = end_of_list;
624 int cur = _hd;
625 while (cur != end_of_list) {
626 if (cur == i) {
627 if (prev == end_of_list) {
628 _hd = _ids[cur];
629 } else {
630 _ids[prev] = _ids[cur];
631 }
632 _ids[cur] = claimed;
633 _claimed++;
634 return true;
635 } else {
636 prev = cur;
637 cur = _ids[cur];
638 }
639 }
640 return false;
641
642 }
643
644 void FreeIdSet::release_par_id(int id) {
645 MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);
646 assert(_ids[id] == claimed, "Precondition.");
647 _ids[id] = _hd;
648 _hd = id;
649 _claimed--;
650 #if FID_STATS
651 tty->print("[%d] release_par_id(%d), waiters =%d, claimed = %d.\n",
652 thr_self(), id, _waiters, _claimed);
653 #endif
654 if (_waiters > 0)
655 // Notify all would be safer, but this is OK, right?
656 _mon->notify_all();
657 }