1 /*
2 * Copyright (c) 2001, 2013, 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/os.hpp"
29 #include "utilities/workgroup.hpp"
30
31 // Definitions of WorkGang methods.
32
33 AbstractWorkGang::AbstractWorkGang(const char* name,
34 bool are_GC_task_threads,
35 bool are_ConcurrentGC_threads) :
36 _name(name),
37 _are_GC_task_threads(are_GC_task_threads),
38 _are_ConcurrentGC_threads(are_ConcurrentGC_threads) {
39
40 assert(!(are_GC_task_threads && are_ConcurrentGC_threads),
41 "They cannot both be STW GC and Concurrent threads" );
42
43 // Other initialization.
44 _monitor = new Monitor(/* priority */ Mutex::leaf,
45 /* name */ "WorkGroup monitor",
46 /* allow_vm_block */ are_GC_task_threads);
47 assert(monitor() != NULL, "Failed to allocate monitor");
48 _terminate = false;
49 _task = NULL;
50 _sequence_number = 0;
51 _started_workers = 0;
52 _finished_workers = 0;
53 }
54
55 WorkGang::WorkGang(const char* name,
56 uint workers,
57 bool are_GC_task_threads,
58 bool are_ConcurrentGC_threads) :
59 AbstractWorkGang(name, are_GC_task_threads, are_ConcurrentGC_threads) {
60 _total_workers = workers;
61 }
62
63 GangWorker* WorkGang::allocate_worker(uint which) {
64 GangWorker* new_worker = new GangWorker(this, which);
65 return new_worker;
66 }
67
68 // The current implementation will exit if the allocation
69 // of any worker fails. Still, return a boolean so that
70 // a future implementation can possibly do a partial
71 // initialization of the workers and report such to the
72 // caller.
73 bool WorkGang::initialize_workers() {
74
75 if (TraceWorkGang) {
76 tty->print_cr("Constructing work gang %s with %d threads",
77 name(),
78 total_workers());
79 }
80 _gang_workers = NEW_C_HEAP_ARRAY(GangWorker*, total_workers(), mtInternal);
81 if (gang_workers() == NULL) {
82 vm_exit_out_of_memory(0, OOM_MALLOC_ERROR, "Cannot create GangWorker array.");
83 return false;
84 }
85 os::ThreadType worker_type;
86 if (are_ConcurrentGC_threads()) {
87 worker_type = os::cgc_thread;
88 } else {
89 worker_type = os::pgc_thread;
90 }
91 for (uint worker = 0; worker < total_workers(); worker += 1) {
92 GangWorker* new_worker = allocate_worker(worker);
93 assert(new_worker != NULL, "Failed to allocate GangWorker");
94 _gang_workers[worker] = new_worker;
95 if (new_worker == NULL || !os::create_thread(new_worker, worker_type)) {
96 vm_exit_out_of_memory(0, OOM_MALLOC_ERROR,
97 "Cannot create worker GC thread. Out of system resources.");
98 return false;
99 }
100 if (!DisableStartThread) {
101 os::start_thread(new_worker);
102 }
103 }
104 return true;
105 }
106
107 AbstractWorkGang::~AbstractWorkGang() {
108 if (TraceWorkGang) {
109 tty->print_cr("Destructing work gang %s", name());
110 }
111 stop(); // stop all the workers
112 for (uint worker = 0; worker < total_workers(); worker += 1) {
113 delete gang_worker(worker);
114 }
115 delete gang_workers();
116 delete monitor();
117 }
118
119 GangWorker* AbstractWorkGang::gang_worker(uint i) const {
120 // Array index bounds checking.
121 GangWorker* result = NULL;
122 assert(gang_workers() != NULL, "No workers for indexing");
123 assert(((i >= 0) && (i < total_workers())), "Worker index out of bounds");
124 result = _gang_workers[i];
125 assert(result != NULL, "Indexing to null worker");
126 return result;
127 }
128
129 void WorkGang::run_task(AbstractGangTask* task) {
130 run_task(task, total_workers());
131 }
132
133 void WorkGang::run_task(AbstractGangTask* task, uint no_of_parallel_workers) {
134 task->set_for_termination(no_of_parallel_workers);
135
136 // This thread is executed by the VM thread which does not block
137 // on ordinary MutexLocker's.
138 MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag);
139 if (TraceWorkGang) {
140 tty->print_cr("Running work gang %s task %s", name(), task->name());
141 }
142 // Tell all the workers to run a task.
143 assert(task != NULL, "Running a null task");
144 // Initialize.
145 _task = task;
146 _sequence_number += 1;
147 _started_workers = 0;
148 _finished_workers = 0;
149 // Tell the workers to get to work.
150 monitor()->notify_all();
151 // Wait for them to be finished
152 while (finished_workers() < no_of_parallel_workers) {
153 if (TraceWorkGang) {
154 tty->print_cr("Waiting in work gang %s: %d/%d finished sequence %d",
155 name(), finished_workers(), no_of_parallel_workers,
156 _sequence_number);
157 }
158 monitor()->wait(/* no_safepoint_check */ true);
159 }
160 _task = NULL;
161 if (TraceWorkGang) {
162 tty->print_cr("\nFinished work gang %s: %d/%d sequence %d",
163 name(), finished_workers(), no_of_parallel_workers,
164 _sequence_number);
165 Thread* me = Thread::current();
166 tty->print_cr(" T: 0x%x VM_thread: %d", me, me->is_VM_thread());
167 }
168 }
169
170 void FlexibleWorkGang::run_task(AbstractGangTask* task) {
171 // If active_workers() is passed, _finished_workers
172 // must only be incremented for workers that find non_null
173 // work (as opposed to all those that just check that the
174 // task is not null).
175 WorkGang::run_task(task, (uint) active_workers());
176 }
177
178 void AbstractWorkGang::stop() {
179 // Tell all workers to terminate, then wait for them to become inactive.
180 MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag);
181 if (TraceWorkGang) {
182 tty->print_cr("Stopping work gang %s task %s", name(), task()->name());
183 }
184 _task = NULL;
185 _terminate = true;
186 monitor()->notify_all();
187 while (finished_workers() < active_workers()) {
188 if (TraceWorkGang) {
189 tty->print_cr("Waiting in work gang %s: %d/%d finished",
190 name(), finished_workers(), active_workers());
191 }
192 monitor()->wait(/* no_safepoint_check */ true);
193 }
194 }
195
196 void AbstractWorkGang::internal_worker_poll(WorkData* data) const {
197 assert(monitor()->owned_by_self(), "worker_poll is an internal method");
198 assert(data != NULL, "worker data is null");
199 data->set_terminate(terminate());
200 data->set_task(task());
201 data->set_sequence_number(sequence_number());
202 }
203
204 void AbstractWorkGang::internal_note_start() {
205 assert(monitor()->owned_by_self(), "note_finish is an internal method");
206 _started_workers += 1;
207 }
208
209 void AbstractWorkGang::internal_note_finish() {
210 assert(monitor()->owned_by_self(), "note_finish is an internal method");
211 _finished_workers += 1;
212 }
213
214 void AbstractWorkGang::print_worker_threads_on(outputStream* st) const {
215 uint num_thr = total_workers();
216 for (uint i = 0; i < num_thr; i++) {
217 gang_worker(i)->print_on(st);
218 st->cr();
219 }
220 }
221
222 void AbstractWorkGang::threads_do(ThreadClosure* tc) const {
223 assert(tc != NULL, "Null ThreadClosure");
224 uint num_thr = total_workers();
225 for (uint i = 0; i < num_thr; i++) {
226 tc->do_thread(gang_worker(i));
227 }
228 }
229
230 // GangWorker methods.
231
232 GangWorker::GangWorker(AbstractWorkGang* gang, uint id) {
233 _gang = gang;
234 set_id(id);
235 set_name("Gang worker#%d (%s)", id, gang->name());
236 }
237
238 void GangWorker::run() {
239 initialize();
240 loop();
241 }
242
243 void GangWorker::initialize() {
244 this->initialize_thread_local_storage();
245 this->record_stack_base_and_size();
246 assert(_gang != NULL, "No gang to run in");
247 os::set_priority(this, NearMaxPriority);
248 if (TraceWorkGang) {
249 tty->print_cr("Running gang worker for gang %s id %d",
250 gang()->name(), id());
251 }
252 // The VM thread should not execute here because MutexLocker's are used
253 // as (opposed to MutexLockerEx's).
254 assert(!Thread::current()->is_VM_thread(), "VM thread should not be part"
255 " of a work gang");
256 }
257
258 void GangWorker::loop() {
259 int previous_sequence_number = 0;
260 Monitor* gang_monitor = gang()->monitor();
261 for ( ; /* !terminate() */; ) {
262 WorkData data;
263 int part; // Initialized below.
264 {
265 // Grab the gang mutex.
266 MutexLocker ml(gang_monitor);
267 // Wait for something to do.
268 // Polling outside the while { wait } avoids missed notifies
269 // in the outer loop.
270 gang()->internal_worker_poll(&data);
271 if (TraceWorkGang) {
272 tty->print("Polled outside for work in gang %s worker %d",
273 gang()->name(), id());
274 tty->print(" terminate: %s",
275 data.terminate() ? "true" : "false");
276 tty->print(" sequence: %d (prev: %d)",
277 data.sequence_number(), previous_sequence_number);
278 if (data.task() != NULL) {
279 tty->print(" task: %s", data.task()->name());
280 } else {
281 tty->print(" task: NULL");
282 }
283 tty->cr();
284 }
285 for ( ; /* break or return */; ) {
286 // Terminate if requested.
287 if (data.terminate()) {
288 gang()->internal_note_finish();
289 gang_monitor->notify_all();
290 return;
291 }
292 // Check for new work.
293 if ((data.task() != NULL) &&
294 (data.sequence_number() != previous_sequence_number)) {
295 if (gang()->needs_more_workers()) {
296 gang()->internal_note_start();
297 gang_monitor->notify_all();
298 part = gang()->started_workers() - 1;
299 break;
300 }
301 }
302 // Nothing to do.
303 gang_monitor->wait(/* no_safepoint_check */ true);
304 gang()->internal_worker_poll(&data);
305 if (TraceWorkGang) {
306 tty->print("Polled inside for work in gang %s worker %d",
307 gang()->name(), id());
308 tty->print(" terminate: %s",
309 data.terminate() ? "true" : "false");
310 tty->print(" sequence: %d (prev: %d)",
311 data.sequence_number(), previous_sequence_number);
312 if (data.task() != NULL) {
313 tty->print(" task: %s", data.task()->name());
314 } else {
315 tty->print(" task: NULL");
316 }
317 tty->cr();
318 }
319 }
320 // Drop gang mutex.
321 }
322 if (TraceWorkGang) {
323 tty->print("Work for work gang %s id %d task %s part %d",
324 gang()->name(), id(), data.task()->name(), part);
325 }
326 assert(data.task() != NULL, "Got null task");
327 data.task()->work(part);
328 {
329 if (TraceWorkGang) {
330 tty->print("Finish for work gang %s id %d task %s part %d",
331 gang()->name(), id(), data.task()->name(), part);
332 }
333 // Grab the gang mutex.
334 MutexLocker ml(gang_monitor);
335 gang()->internal_note_finish();
336 // Tell the gang you are done.
337 gang_monitor->notify_all();
338 // Drop the gang mutex.
339 }
340 previous_sequence_number = data.sequence_number();
341 }
342 }
343
344 bool GangWorker::is_GC_task_thread() const {
345 return gang()->are_GC_task_threads();
346 }
347
348 bool GangWorker::is_ConcurrentGC_thread() const {
349 return gang()->are_ConcurrentGC_threads();
350 }
351
352 void GangWorker::print_on(outputStream* st) const {
353 st->print("\"%s\" ", name());
354 Thread::print_on(st);
355 st->cr();
356 }
357
358 // Printing methods
359
360 const char* AbstractWorkGang::name() const {
361 return _name;
362 }
363
364 #ifndef PRODUCT
365
366 const char* AbstractGangTask::name() const {
367 return _name;
368 }
369
370 #endif /* PRODUCT */
371
372 // FlexibleWorkGang
373
374
375 // *** WorkGangBarrierSync
376
377 WorkGangBarrierSync::WorkGangBarrierSync()
378 : _monitor(Mutex::safepoint, "work gang barrier sync", true),
379 _n_workers(0), _n_completed(0), _should_reset(false) {
380 }
381
382 WorkGangBarrierSync::WorkGangBarrierSync(uint n_workers, const char* name)
383 : _monitor(Mutex::safepoint, name, true),
384 _n_workers(n_workers), _n_completed(0), _should_reset(false) {
385 }
386
387 void WorkGangBarrierSync::set_n_workers(uint n_workers) {
388 _n_workers = n_workers;
389 _n_completed = 0;
390 _should_reset = false;
391 }
392
393 void WorkGangBarrierSync::enter() {
394 MutexLockerEx x(monitor(), Mutex::_no_safepoint_check_flag);
395 if (should_reset()) {
396 // The should_reset() was set and we are the first worker to enter
397 // the sync barrier. We will zero the n_completed() count which
398 // effectively resets the barrier.
399 zero_completed();
400 set_should_reset(false);
401 }
402 inc_completed();
403 if (n_completed() == n_workers()) {
404 // At this point we would like to reset the barrier to be ready in
405 // case it is used again. However, we cannot set n_completed() to
406 // 0, even after the notify_all(), given that some other workers
407 // might still be waiting for n_completed() to become ==
408 // n_workers(). So, if we set n_completed() to 0, those workers
409 // will get stuck (as they will wake up, see that n_completed() !=
410 // n_workers() and go back to sleep). Instead, we raise the
411 // should_reset() flag and the barrier will be reset the first
412 // time a worker enters it again.
413 set_should_reset(true);
414 monitor()->notify_all();
415 } else {
416 while (n_completed() != n_workers()) {
417 monitor()->wait(/* no_safepoint_check */ true);
418 }
419 }
420 }
421
422 // SubTasksDone functions.
423
424 SubTasksDone::SubTasksDone(uint n) :
425 _n_tasks(n), _n_threads(1), _tasks(NULL) {
426 _tasks = NEW_C_HEAP_ARRAY(uint, n, mtInternal);
427 guarantee(_tasks != NULL, "alloc failure");
428 clear();
429 }
430
431 bool SubTasksDone::valid() {
432 return _tasks != NULL;
433 }
434
435 void SubTasksDone::set_n_threads(uint t) {
436 assert(_claimed == 0 || _threads_completed == _n_threads,
437 "should not be called while tasks are being processed!");
438 _n_threads = (t == 0 ? 1 : t);
439 }
440
441 void SubTasksDone::clear() {
442 for (uint i = 0; i < _n_tasks; i++) {
443 _tasks[i] = 0;
444 }
445 _threads_completed = 0;
446 #ifdef ASSERT
447 _claimed = 0;
448 #endif
449 }
450
451 bool SubTasksDone::is_task_claimed(uint t) {
452 assert(0 <= t && t < _n_tasks, "bad task id.");
453 uint old = _tasks[t];
454 if (old == 0) {
455 old = Atomic::cmpxchg(1, &_tasks[t], 0);
456 }
457 assert(_tasks[t] == 1, "What else?");
458 bool res = old != 0;
459 #ifdef ASSERT
460 if (!res) {
461 assert(_claimed < _n_tasks, "Too many tasks claimed; missing clear?");
462 Atomic::inc((volatile jint*) &_claimed);
463 }
464 #endif
465 return res;
466 }
467
468 void SubTasksDone::all_tasks_completed() {
469 jint observed = _threads_completed;
470 jint old;
471 do {
472 old = observed;
473 observed = Atomic::cmpxchg(old+1, &_threads_completed, old);
474 } while (observed != old);
475 // If this was the last thread checking in, clear the tasks.
476 if (observed+1 == (jint)_n_threads) clear();
477 }
478
479
480 SubTasksDone::~SubTasksDone() {
481 if (_tasks != NULL) FREE_C_HEAP_ARRAY(jint, _tasks, mtInternal);
482 }
483
484 // *** SequentialSubTasksDone
485
486 void SequentialSubTasksDone::clear() {
487 _n_tasks = _n_claimed = 0;
488 _n_threads = _n_completed = 0;
489 }
490
491 bool SequentialSubTasksDone::valid() {
492 return _n_threads > 0;
493 }
494
495 bool SequentialSubTasksDone::is_task_claimed(uint& t) {
496 uint* n_claimed_ptr = &_n_claimed;
497 t = *n_claimed_ptr;
498 while (t < _n_tasks) {
499 jint res = Atomic::cmpxchg(t+1, n_claimed_ptr, t);
500 if (res == (jint)t) {
501 return false;
502 }
503 t = *n_claimed_ptr;
504 }
505 return true;
506 }
507
508 bool SequentialSubTasksDone::all_tasks_completed() {
509 uint* n_completed_ptr = &_n_completed;
510 uint complete = *n_completed_ptr;
511 while (true) {
512 uint res = Atomic::cmpxchg(complete+1, n_completed_ptr, complete);
513 if (res == complete) {
514 break;
515 }
516 complete = res;
517 }
518 if (complete+1 == _n_threads) {
519 clear();
520 return true;
521 }
522 return false;
523 }
524
525 bool FreeIdSet::_stat_init = false;
526 FreeIdSet* FreeIdSet::_sets[NSets];
527 bool FreeIdSet::_safepoint;
528
529 FreeIdSet::FreeIdSet(int sz, Monitor* mon) :
530 _sz(sz), _mon(mon), _hd(0), _waiters(0), _index(-1), _claimed(0)
531 {
532 _ids = NEW_C_HEAP_ARRAY(int, sz, mtInternal);
533 for (int i = 0; i < sz; i++) _ids[i] = i+1;
534 _ids[sz-1] = end_of_list; // end of list.
535 if (_stat_init) {
536 for (int j = 0; j < NSets; j++) _sets[j] = NULL;
537 _stat_init = true;
538 }
539 // Add to sets. (This should happen while the system is still single-threaded.)
540 for (int j = 0; j < NSets; j++) {
541 if (_sets[j] == NULL) {
542 _sets[j] = this;
543 _index = j;
544 break;
545 }
546 }
547 guarantee(_index != -1, "Too many FreeIdSets in use!");
548 }
549
550 FreeIdSet::~FreeIdSet() {
551 _sets[_index] = NULL;
552 FREE_C_HEAP_ARRAY(int, _ids, mtInternal);
553 }
554
555 void FreeIdSet::set_safepoint(bool b) {
556 _safepoint = b;
557 if (b) {
558 for (int j = 0; j < NSets; j++) {
559 if (_sets[j] != NULL && _sets[j]->_waiters > 0) {
560 Monitor* mon = _sets[j]->_mon;
561 mon->lock_without_safepoint_check();
562 mon->notify_all();
563 mon->unlock();
564 }
565 }
566 }
567 }
568
569 #define FID_STATS 0
570
571 int FreeIdSet::claim_par_id() {
572 #if FID_STATS
573 thread_t tslf = thr_self();
574 tty->print("claim_par_id[%d]: sz = %d, claimed = %d\n", tslf, _sz, _claimed);
575 #endif
576 MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);
577 while (!_safepoint && _hd == end_of_list) {
578 _waiters++;
579 #if FID_STATS
580 if (_waiters > 5) {
581 tty->print("claim_par_id waiting[%d]: %d waiters, %d claimed.\n",
582 tslf, _waiters, _claimed);
583 }
584 #endif
585 _mon->wait(Mutex::_no_safepoint_check_flag);
586 _waiters--;
587 }
588 if (_hd == end_of_list) {
589 #if FID_STATS
590 tty->print("claim_par_id[%d]: returning EOL.\n", tslf);
591 #endif
592 return -1;
593 } else {
594 int res = _hd;
595 _hd = _ids[res];
596 _ids[res] = claimed; // For debugging.
597 _claimed++;
598 #if FID_STATS
599 tty->print("claim_par_id[%d]: returning %d, claimed = %d.\n",
600 tslf, res, _claimed);
601 #endif
602 return res;
603 }
604 }
605
606 bool FreeIdSet::claim_perm_id(int i) {
607 assert(0 <= i && i < _sz, "Out of range.");
608 MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);
609 int prev = end_of_list;
610 int cur = _hd;
611 while (cur != end_of_list) {
612 if (cur == i) {
613 if (prev == end_of_list) {
614 _hd = _ids[cur];
615 } else {
616 _ids[prev] = _ids[cur];
617 }
618 _ids[cur] = claimed;
619 _claimed++;
620 return true;
621 } else {
622 prev = cur;
623 cur = _ids[cur];
624 }
625 }
626 return false;
627
628 }
629
630 void FreeIdSet::release_par_id(int id) {
631 MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);
632 assert(_ids[id] == claimed, "Precondition.");
633 _ids[id] = _hd;
634 _hd = id;
635 _claimed--;
636 #if FID_STATS
637 tty->print("[%d] release_par_id(%d), waiters =%d, claimed = %d.\n",
638 thr_self(), id, _waiters, _claimed);
639 #endif
640 if (_waiters > 0)
641 // Notify all would be safer, but this is OK, right?
642 _mon->notify_all();
643 }