1 /*
2 * Copyright (c) 2001, 2007, 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 "incls/_precompiled.incl"
26 # include "incls/_workgroup.cpp.incl"
27
28 // Definitions of WorkGang methods.
29
30 AbstractWorkGang::AbstractWorkGang(const char* name,
31 bool are_GC_task_threads,
32 bool are_ConcurrentGC_threads) :
33 _name(name),
34 _are_GC_task_threads(are_GC_task_threads),
35 _are_ConcurrentGC_threads(are_ConcurrentGC_threads) {
36
37 assert(!(are_GC_task_threads && are_ConcurrentGC_threads),
38 "They cannot both be STW GC and Concurrent threads" );
39
40 // Other initialization.
41 _monitor = new Monitor(/* priority */ Mutex::leaf,
42 /* name */ "WorkGroup monitor",
43 /* allow_vm_block */ are_GC_task_threads);
44 assert(monitor() != NULL, "Failed to allocate monitor");
45 _terminate = false;
46 _task = NULL;
47 _sequence_number = 0;
48 _started_workers = 0;
49 _finished_workers = 0;
50 }
51
52 WorkGang::WorkGang(const char* name,
53 int workers,
54 bool are_GC_task_threads,
55 bool are_ConcurrentGC_threads) :
56 AbstractWorkGang(name, are_GC_task_threads, are_ConcurrentGC_threads)
57 {
58 // Save arguments.
59 _total_workers = workers;
60
61 if (TraceWorkGang) {
62 tty->print_cr("Constructing work gang %s with %d threads", name, workers);
63 }
64 _gang_workers = NEW_C_HEAP_ARRAY(GangWorker*, workers);
65 if (gang_workers() == NULL) {
66 vm_exit_out_of_memory(0, "Cannot create GangWorker array.");
67 }
68 for (int worker = 0; worker < total_workers(); worker += 1) {
69 GangWorker* new_worker = new GangWorker(this, worker);
70 assert(new_worker != NULL, "Failed to allocate GangWorker");
71 _gang_workers[worker] = new_worker;
72 if (new_worker == NULL || !os::create_thread(new_worker, os::pgc_thread))
73 vm_exit_out_of_memory(0, "Cannot create worker GC thread. Out of system resources.");
74 if (!DisableStartThread) {
75 os::start_thread(new_worker);
76 }
77 }
78 }
79
80 AbstractWorkGang::~AbstractWorkGang() {
81 if (TraceWorkGang) {
82 tty->print_cr("Destructing work gang %s", name());
83 }
84 stop(); // stop all the workers
85 for (int worker = 0; worker < total_workers(); worker += 1) {
86 delete gang_worker(worker);
87 }
88 delete gang_workers();
89 delete monitor();
90 }
91
92 GangWorker* AbstractWorkGang::gang_worker(int i) const {
93 // Array index bounds checking.
94 GangWorker* result = NULL;
95 assert(gang_workers() != NULL, "No workers for indexing");
96 assert(((i >= 0) && (i < total_workers())), "Worker index out of bounds");
97 result = _gang_workers[i];
98 assert(result != NULL, "Indexing to null worker");
99 return result;
100 }
101
102 void WorkGang::run_task(AbstractGangTask* task) {
103 // This thread is executed by the VM thread which does not block
104 // on ordinary MutexLocker's.
105 MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag);
106 if (TraceWorkGang) {
107 tty->print_cr("Running work gang %s task %s", name(), task->name());
108 }
109 // Tell all the workers to run a task.
110 assert(task != NULL, "Running a null task");
111 // Initialize.
112 _task = task;
113 _sequence_number += 1;
114 _started_workers = 0;
115 _finished_workers = 0;
116 // Tell the workers to get to work.
117 monitor()->notify_all();
118 // Wait for them to be finished
119 while (finished_workers() < total_workers()) {
120 if (TraceWorkGang) {
121 tty->print_cr("Waiting in work gang %s: %d/%d finished sequence %d",
122 name(), finished_workers(), total_workers(),
123 _sequence_number);
124 }
125 monitor()->wait(/* no_safepoint_check */ true);
126 }
127 _task = NULL;
128 if (TraceWorkGang) {
129 tty->print_cr("/nFinished work gang %s: %d/%d sequence %d",
130 name(), finished_workers(), total_workers(),
131 _sequence_number);
132 }
133 }
134
135 void AbstractWorkGang::stop() {
136 // Tell all workers to terminate, then wait for them to become inactive.
137 MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag);
138 if (TraceWorkGang) {
139 tty->print_cr("Stopping work gang %s task %s", name(), task()->name());
140 }
141 _task = NULL;
142 _terminate = true;
143 monitor()->notify_all();
144 while (finished_workers() < total_workers()) {
145 if (TraceWorkGang) {
146 tty->print_cr("Waiting in work gang %s: %d/%d finished",
147 name(), finished_workers(), total_workers());
148 }
149 monitor()->wait(/* no_safepoint_check */ true);
150 }
151 }
152
153 void AbstractWorkGang::internal_worker_poll(WorkData* data) const {
154 assert(monitor()->owned_by_self(), "worker_poll is an internal method");
155 assert(data != NULL, "worker data is null");
156 data->set_terminate(terminate());
157 data->set_task(task());
158 data->set_sequence_number(sequence_number());
159 }
160
161 void AbstractWorkGang::internal_note_start() {
162 assert(monitor()->owned_by_self(), "note_finish is an internal method");
163 _started_workers += 1;
164 }
165
166 void AbstractWorkGang::internal_note_finish() {
167 assert(monitor()->owned_by_self(), "note_finish is an internal method");
168 _finished_workers += 1;
169 }
170
171 void AbstractWorkGang::print_worker_threads_on(outputStream* st) const {
172 uint num_thr = total_workers();
173 for (uint i = 0; i < num_thr; i++) {
174 gang_worker(i)->print_on(st);
175 st->cr();
176 }
177 }
178
179 void AbstractWorkGang::threads_do(ThreadClosure* tc) const {
180 assert(tc != NULL, "Null ThreadClosure");
181 uint num_thr = total_workers();
182 for (uint i = 0; i < num_thr; i++) {
183 tc->do_thread(gang_worker(i));
184 }
185 }
186
187 // GangWorker methods.
188
189 GangWorker::GangWorker(AbstractWorkGang* gang, uint id) {
190 _gang = gang;
191 set_id(id);
192 set_name("Gang worker#%d (%s)", id, gang->name());
193 }
194
195 void GangWorker::run() {
196 initialize();
197 loop();
198 }
199
200 void GangWorker::initialize() {
201 this->initialize_thread_local_storage();
202 assert(_gang != NULL, "No gang to run in");
203 os::set_priority(this, NearMaxPriority);
204 if (TraceWorkGang) {
205 tty->print_cr("Running gang worker for gang %s id %d",
206 gang()->name(), id());
207 }
208 // The VM thread should not execute here because MutexLocker's are used
209 // as (opposed to MutexLockerEx's).
210 assert(!Thread::current()->is_VM_thread(), "VM thread should not be part"
211 " of a work gang");
212 }
213
214 void GangWorker::loop() {
215 int previous_sequence_number = 0;
216 Monitor* gang_monitor = gang()->monitor();
217 for ( ; /* !terminate() */; ) {
218 WorkData data;
219 int part; // Initialized below.
220 {
221 // Grab the gang mutex.
222 MutexLocker ml(gang_monitor);
223 // Wait for something to do.
224 // Polling outside the while { wait } avoids missed notifies
225 // in the outer loop.
226 gang()->internal_worker_poll(&data);
227 if (TraceWorkGang) {
228 tty->print("Polled outside for work in gang %s worker %d",
229 gang()->name(), id());
230 tty->print(" terminate: %s",
231 data.terminate() ? "true" : "false");
232 tty->print(" sequence: %d (prev: %d)",
233 data.sequence_number(), previous_sequence_number);
234 if (data.task() != NULL) {
235 tty->print(" task: %s", data.task()->name());
236 } else {
237 tty->print(" task: NULL");
238 }
239 tty->cr();
240 }
241 for ( ; /* break or return */; ) {
242 // Terminate if requested.
243 if (data.terminate()) {
244 gang()->internal_note_finish();
245 gang_monitor->notify_all();
246 return;
247 }
248 // Check for new work.
249 if ((data.task() != NULL) &&
250 (data.sequence_number() != previous_sequence_number)) {
251 gang()->internal_note_start();
252 gang_monitor->notify_all();
253 part = gang()->started_workers() - 1;
254 break;
255 }
256 // Nothing to do.
257 gang_monitor->wait(/* no_safepoint_check */ true);
258 gang()->internal_worker_poll(&data);
259 if (TraceWorkGang) {
260 tty->print("Polled inside for work in gang %s worker %d",
261 gang()->name(), id());
262 tty->print(" terminate: %s",
263 data.terminate() ? "true" : "false");
264 tty->print(" sequence: %d (prev: %d)",
265 data.sequence_number(), previous_sequence_number);
266 if (data.task() != NULL) {
267 tty->print(" task: %s", data.task()->name());
268 } else {
269 tty->print(" task: NULL");
270 }
271 tty->cr();
272 }
273 }
274 // Drop gang mutex.
275 }
276 if (TraceWorkGang) {
277 tty->print("Work for work gang %s id %d task %s part %d",
278 gang()->name(), id(), data.task()->name(), part);
279 }
280 assert(data.task() != NULL, "Got null task");
281 data.task()->work(part);
282 {
283 if (TraceWorkGang) {
284 tty->print("Finish for work gang %s id %d task %s part %d",
285 gang()->name(), id(), data.task()->name(), part);
286 }
287 // Grab the gang mutex.
288 MutexLocker ml(gang_monitor);
289 gang()->internal_note_finish();
290 // Tell the gang you are done.
291 gang_monitor->notify_all();
292 // Drop the gang mutex.
293 }
294 previous_sequence_number = data.sequence_number();
295 }
296 }
297
298 bool GangWorker::is_GC_task_thread() const {
299 return gang()->are_GC_task_threads();
300 }
301
302 bool GangWorker::is_ConcurrentGC_thread() const {
303 return gang()->are_ConcurrentGC_threads();
304 }
305
306 void GangWorker::print_on(outputStream* st) const {
307 st->print("\"%s\" ", name());
308 Thread::print_on(st);
309 st->cr();
310 }
311
312 // Printing methods
313
314 const char* AbstractWorkGang::name() const {
315 return _name;
316 }
317
318 #ifndef PRODUCT
319
320 const char* AbstractGangTask::name() const {
321 return _name;
322 }
323
324 #endif /* PRODUCT */
325
326 // *** WorkGangBarrierSync
327
328 WorkGangBarrierSync::WorkGangBarrierSync()
329 : _monitor(Mutex::safepoint, "work gang barrier sync", true),
330 _n_workers(0), _n_completed(0), _should_reset(false) {
331 }
332
333 WorkGangBarrierSync::WorkGangBarrierSync(int n_workers, const char* name)
334 : _monitor(Mutex::safepoint, name, true),
335 _n_workers(n_workers), _n_completed(0), _should_reset(false) {
336 }
337
338 void WorkGangBarrierSync::set_n_workers(int n_workers) {
339 _n_workers = n_workers;
340 _n_completed = 0;
341 _should_reset = false;
342 }
343
344 void WorkGangBarrierSync::enter() {
345 MutexLockerEx x(monitor(), Mutex::_no_safepoint_check_flag);
346 if (should_reset()) {
347 // The should_reset() was set and we are the first worker to enter
348 // the sync barrier. We will zero the n_completed() count which
349 // effectively resets the barrier.
350 zero_completed();
351 set_should_reset(false);
352 }
353 inc_completed();
354 if (n_completed() == n_workers()) {
355 // At this point we would like to reset the barrier to be ready in
356 // case it is used again. However, we cannot set n_completed() to
357 // 0, even after the notify_all(), given that some other workers
358 // might still be waiting for n_completed() to become ==
359 // n_workers(). So, if we set n_completed() to 0, those workers
360 // will get stuck (as they will wake up, see that n_completed() !=
361 // n_workers() and go back to sleep). Instead, we raise the
362 // should_reset() flag and the barrier will be reset the first
363 // time a worker enters it again.
364 set_should_reset(true);
365 monitor()->notify_all();
366 } else {
367 while (n_completed() != n_workers()) {
368 monitor()->wait(/* no_safepoint_check */ true);
369 }
370 }
371 }
372
373 // SubTasksDone functions.
374
375 SubTasksDone::SubTasksDone(int n) :
376 _n_tasks(n), _n_threads(1), _tasks(NULL) {
377 _tasks = NEW_C_HEAP_ARRAY(jint, n);
378 guarantee(_tasks != NULL, "alloc failure");
379 clear();
380 }
381
382 bool SubTasksDone::valid() {
383 return _tasks != NULL;
384 }
385
386 void SubTasksDone::set_par_threads(int t) {
387 #ifdef ASSERT
388 assert(_claimed == 0 || _threads_completed == _n_threads,
389 "should not be called while tasks are being processed!");
390 #endif
391 _n_threads = (t == 0 ? 1 : t);
392 }
393
394 void SubTasksDone::clear() {
395 for (int i = 0; i < _n_tasks; i++) {
396 _tasks[i] = 0;
397 }
398 _threads_completed = 0;
399 #ifdef ASSERT
400 _claimed = 0;
401 #endif
402 }
403
404 bool SubTasksDone::is_task_claimed(int t) {
405 assert(0 <= t && t < _n_tasks, "bad task id.");
406 jint old = _tasks[t];
407 if (old == 0) {
408 old = Atomic::cmpxchg(1, &_tasks[t], 0);
409 }
410 assert(_tasks[t] == 1, "What else?");
411 bool res = old != 0;
412 #ifdef ASSERT
413 if (!res) {
414 assert(_claimed < _n_tasks, "Too many tasks claimed; missing clear?");
415 Atomic::inc(&_claimed);
416 }
417 #endif
418 return res;
419 }
420
421 void SubTasksDone::all_tasks_completed() {
422 jint observed = _threads_completed;
423 jint old;
424 do {
425 old = observed;
426 observed = Atomic::cmpxchg(old+1, &_threads_completed, old);
427 } while (observed != old);
428 // If this was the last thread checking in, clear the tasks.
429 if (observed+1 == _n_threads) clear();
430 }
431
432
433 SubTasksDone::~SubTasksDone() {
434 if (_tasks != NULL) FREE_C_HEAP_ARRAY(jint, _tasks);
435 }
436
437 // *** SequentialSubTasksDone
438
439 void SequentialSubTasksDone::clear() {
440 _n_tasks = _n_claimed = 0;
441 _n_threads = _n_completed = 0;
442 }
443
444 bool SequentialSubTasksDone::valid() {
445 return _n_threads > 0;
446 }
447
448 bool SequentialSubTasksDone::is_task_claimed(int& t) {
449 jint* n_claimed_ptr = &_n_claimed;
450 t = *n_claimed_ptr;
451 while (t < _n_tasks) {
452 jint res = Atomic::cmpxchg(t+1, n_claimed_ptr, t);
453 if (res == t) {
454 return false;
455 }
456 t = *n_claimed_ptr;
457 }
458 return true;
459 }
460
461 bool SequentialSubTasksDone::all_tasks_completed() {
462 jint* n_completed_ptr = &_n_completed;
463 jint complete = *n_completed_ptr;
464 while (true) {
465 jint res = Atomic::cmpxchg(complete+1, n_completed_ptr, complete);
466 if (res == complete) {
467 break;
468 }
469 complete = res;
470 }
471 if (complete+1 == _n_threads) {
472 clear();
473 return true;
474 }
475 return false;
476 }
477
478 bool FreeIdSet::_stat_init = false;
479 FreeIdSet* FreeIdSet::_sets[NSets];
480 bool FreeIdSet::_safepoint;
481
482 FreeIdSet::FreeIdSet(int sz, Monitor* mon) :
483 _sz(sz), _mon(mon), _hd(0), _waiters(0), _index(-1), _claimed(0)
484 {
485 _ids = new int[sz];
486 for (int i = 0; i < sz; i++) _ids[i] = i+1;
487 _ids[sz-1] = end_of_list; // end of list.
488 if (_stat_init) {
489 for (int j = 0; j < NSets; j++) _sets[j] = NULL;
490 _stat_init = true;
491 }
492 // Add to sets. (This should happen while the system is still single-threaded.)
493 for (int j = 0; j < NSets; j++) {
494 if (_sets[j] == NULL) {
495 _sets[j] = this;
496 _index = j;
497 break;
498 }
499 }
500 guarantee(_index != -1, "Too many FreeIdSets in use!");
501 }
502
503 FreeIdSet::~FreeIdSet() {
504 _sets[_index] = NULL;
505 }
506
507 void FreeIdSet::set_safepoint(bool b) {
508 _safepoint = b;
509 if (b) {
510 for (int j = 0; j < NSets; j++) {
511 if (_sets[j] != NULL && _sets[j]->_waiters > 0) {
512 Monitor* mon = _sets[j]->_mon;
513 mon->lock_without_safepoint_check();
514 mon->notify_all();
515 mon->unlock();
516 }
517 }
518 }
519 }
520
521 #define FID_STATS 0
522
523 int FreeIdSet::claim_par_id() {
524 #if FID_STATS
525 thread_t tslf = thr_self();
526 tty->print("claim_par_id[%d]: sz = %d, claimed = %d\n", tslf, _sz, _claimed);
527 #endif
528 MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);
529 while (!_safepoint && _hd == end_of_list) {
530 _waiters++;
531 #if FID_STATS
532 if (_waiters > 5) {
533 tty->print("claim_par_id waiting[%d]: %d waiters, %d claimed.\n",
534 tslf, _waiters, _claimed);
535 }
536 #endif
537 _mon->wait(Mutex::_no_safepoint_check_flag);
538 _waiters--;
539 }
540 if (_hd == end_of_list) {
541 #if FID_STATS
542 tty->print("claim_par_id[%d]: returning EOL.\n", tslf);
543 #endif
544 return -1;
545 } else {
546 int res = _hd;
547 _hd = _ids[res];
548 _ids[res] = claimed; // For debugging.
549 _claimed++;
550 #if FID_STATS
551 tty->print("claim_par_id[%d]: returning %d, claimed = %d.\n",
552 tslf, res, _claimed);
553 #endif
554 return res;
555 }
556 }
557
558 bool FreeIdSet::claim_perm_id(int i) {
559 assert(0 <= i && i < _sz, "Out of range.");
560 MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);
561 int prev = end_of_list;
562 int cur = _hd;
563 while (cur != end_of_list) {
564 if (cur == i) {
565 if (prev == end_of_list) {
566 _hd = _ids[cur];
567 } else {
568 _ids[prev] = _ids[cur];
569 }
570 _ids[cur] = claimed;
571 _claimed++;
572 return true;
573 } else {
574 prev = cur;
575 cur = _ids[cur];
576 }
577 }
578 return false;
579
580 }
581
582 void FreeIdSet::release_par_id(int id) {
583 MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);
584 assert(_ids[id] == claimed, "Precondition.");
585 _ids[id] = _hd;
586 _hd = id;
587 _claimed--;
588 #if FID_STATS
589 tty->print("[%d] release_par_id(%d), waiters =%d, claimed = %d.\n",
590 thr_self(), id, _waiters, _claimed);
591 #endif
592 if (_waiters > 0)
593 // Notify all would be safer, but this is OK, right?
594 _mon->notify_all();
595 }