1 /*
2 * Copyright (c) 2001, 2010, 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 // Save arguments.
58 _total_workers = workers;
59 }
60
61 GangWorker* WorkGang::allocate_worker(int which) {
62 GangWorker* new_worker = new GangWorker(this, which);
63 return new_worker;
64 }
65
66 // The current implementation will exit if the allocation
67 // of any worker fails. Still, return a boolean so that
68 // a future implementation can possibly do a partial
69 // initialization of the workers and report such to the
70 // caller.
71 bool WorkGang::initialize_workers() {
72
73 if (TraceWorkGang) {
74 tty->print_cr("Constructing work gang %s with %d threads",
75 name(),
76 total_workers());
77 }
78 _gang_workers = NEW_C_HEAP_ARRAY(GangWorker*, total_workers());
79 if (gang_workers() == NULL) {
80 vm_exit_out_of_memory(0, "Cannot create GangWorker array.");
81 return false;
82 }
83 os::ThreadType worker_type;
84 if (are_ConcurrentGC_threads()) {
85 worker_type = os::cgc_thread;
86 } else {
87 worker_type = os::pgc_thread;
88 }
89 for (int worker = 0; worker < total_workers(); worker += 1) {
90 GangWorker* new_worker = allocate_worker(worker);
91 assert(new_worker != NULL, "Failed to allocate GangWorker");
92 _gang_workers[worker] = new_worker;
93 if (new_worker == NULL || !os::create_thread(new_worker, worker_type)) {
94 vm_exit_out_of_memory(0, "Cannot create worker GC thread. Out of system resources.");
95 return false;
96 }
97 if (!DisableStartThread) {
98 os::start_thread(new_worker);
99 }
100 }
101 return true;
102 }
103
104 AbstractWorkGang::~AbstractWorkGang() {
105 if (TraceWorkGang) {
106 tty->print_cr("Destructing work gang %s", name());
107 }
108 stop(); // stop all the workers
109 for (int worker = 0; worker < total_workers(); worker += 1) {
110 delete gang_worker(worker);
111 }
112 delete gang_workers();
113 delete monitor();
114 }
115
116 GangWorker* AbstractWorkGang::gang_worker(int i) const {
117 // Array index bounds checking.
118 GangWorker* result = NULL;
119 assert(gang_workers() != NULL, "No workers for indexing");
120 assert(((i >= 0) && (i < total_workers())), "Worker index out of bounds");
121 result = _gang_workers[i];
122 assert(result != NULL, "Indexing to null worker");
123 return result;
124 }
125
126 void WorkGang::run_task(AbstractGangTask* task) {
127 // This thread is executed by the VM thread which does not block
128 // on ordinary MutexLocker's.
129 MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag);
130 if (TraceWorkGang) {
131 tty->print_cr("Running work gang %s task %s", name(), task->name());
132 }
133 // Tell all the workers to run a task.
134 assert(task != NULL, "Running a null task");
135 // Initialize.
136 _task = task;
137 _sequence_number += 1;
138 _started_workers = 0;
139 _finished_workers = 0;
140 // Tell the workers to get to work.
141 monitor()->notify_all();
142 // Wait for them to be finished
143 while (finished_workers() < total_workers()) {
144 if (TraceWorkGang) {
145 tty->print_cr("Waiting in work gang %s: %d/%d finished sequence %d",
146 name(), finished_workers(), total_workers(),
147 _sequence_number);
148 }
149 monitor()->wait(/* no_safepoint_check */ true);
150 }
151 _task = NULL;
152 if (TraceWorkGang) {
153 tty->print_cr("/nFinished work gang %s: %d/%d sequence %d",
154 name(), finished_workers(), total_workers(),
155 _sequence_number);
156 }
157 }
158
159 void AbstractWorkGang::stop() {
160 // Tell all workers to terminate, then wait for them to become inactive.
161 MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag);
162 if (TraceWorkGang) {
163 tty->print_cr("Stopping work gang %s task %s", name(), task()->name());
164 }
165 _task = NULL;
166 _terminate = true;
167 monitor()->notify_all();
168 while (finished_workers() < total_workers()) {
169 if (TraceWorkGang) {
170 tty->print_cr("Waiting in work gang %s: %d/%d finished",
171 name(), finished_workers(), total_workers());
172 }
173 monitor()->wait(/* no_safepoint_check */ true);
174 }
175 }
176
177 void AbstractWorkGang::internal_worker_poll(WorkData* data) const {
178 assert(monitor()->owned_by_self(), "worker_poll is an internal method");
179 assert(data != NULL, "worker data is null");
180 data->set_terminate(terminate());
181 data->set_task(task());
182 data->set_sequence_number(sequence_number());
183 }
184
185 void AbstractWorkGang::internal_note_start() {
186 assert(monitor()->owned_by_self(), "note_finish is an internal method");
187 _started_workers += 1;
188 }
189
190 void AbstractWorkGang::internal_note_finish() {
191 assert(monitor()->owned_by_self(), "note_finish is an internal method");
192 _finished_workers += 1;
193 }
194
195 void AbstractWorkGang::print_worker_threads_on(outputStream* st) const {
196 uint num_thr = total_workers();
197 for (uint i = 0; i < num_thr; i++) {
198 gang_worker(i)->print_on(st);
199 st->cr();
200 }
201 }
202
203 void AbstractWorkGang::threads_do(ThreadClosure* tc) const {
204 assert(tc != NULL, "Null ThreadClosure");
205 uint num_thr = total_workers();
206 for (uint i = 0; i < num_thr; i++) {
207 tc->do_thread(gang_worker(i));
208 }
209 }
210
211 // GangWorker methods.
212
213 GangWorker::GangWorker(AbstractWorkGang* gang, uint id) {
214 _gang = gang;
215 set_id(id);
216 set_name("Gang worker#%d (%s)", id, gang->name());
217 }
218
219 void GangWorker::run() {
220 initialize();
221 loop();
222 }
223
224 void GangWorker::initialize() {
225 this->initialize_thread_local_storage();
226 assert(_gang != NULL, "No gang to run in");
227 os::set_priority(this, NearMaxPriority);
228 if (TraceWorkGang) {
229 tty->print_cr("Running gang worker for gang %s id %d",
230 gang()->name(), id());
231 }
232 // The VM thread should not execute here because MutexLocker's are used
233 // as (opposed to MutexLockerEx's).
234 assert(!Thread::current()->is_VM_thread(), "VM thread should not be part"
235 " of a work gang");
236 }
237
238 void GangWorker::loop() {
239 int previous_sequence_number = 0;
240 Monitor* gang_monitor = gang()->monitor();
241 for ( ; /* !terminate() */; ) {
242 WorkData data;
243 int part; // Initialized below.
244 {
245 // Grab the gang mutex.
246 MutexLocker ml(gang_monitor);
247 // Wait for something to do.
248 // Polling outside the while { wait } avoids missed notifies
249 // in the outer loop.
250 gang()->internal_worker_poll(&data);
251 if (TraceWorkGang) {
252 tty->print("Polled outside for work in gang %s worker %d",
253 gang()->name(), id());
254 tty->print(" terminate: %s",
255 data.terminate() ? "true" : "false");
256 tty->print(" sequence: %d (prev: %d)",
257 data.sequence_number(), previous_sequence_number);
258 if (data.task() != NULL) {
259 tty->print(" task: %s", data.task()->name());
260 } else {
261 tty->print(" task: NULL");
262 }
263 tty->cr();
264 }
265 for ( ; /* break or return */; ) {
266 // Terminate if requested.
267 if (data.terminate()) {
268 gang()->internal_note_finish();
269 gang_monitor->notify_all();
270 return;
271 }
272 // Check for new work.
273 if ((data.task() != NULL) &&
274 (data.sequence_number() != previous_sequence_number)) {
275 gang()->internal_note_start();
276 gang_monitor->notify_all();
277 part = gang()->started_workers() - 1;
278 break;
279 }
280 // Nothing to do.
281 gang_monitor->wait(/* no_safepoint_check */ true);
282 gang()->internal_worker_poll(&data);
283 if (TraceWorkGang) {
284 tty->print("Polled inside for work in gang %s worker %d",
285 gang()->name(), id());
286 tty->print(" terminate: %s",
287 data.terminate() ? "true" : "false");
288 tty->print(" sequence: %d (prev: %d)",
289 data.sequence_number(), previous_sequence_number);
290 if (data.task() != NULL) {
291 tty->print(" task: %s", data.task()->name());
292 } else {
293 tty->print(" task: NULL");
294 }
295 tty->cr();
296 }
297 }
298 // Drop gang mutex.
299 }
300 if (TraceWorkGang) {
301 tty->print("Work for work gang %s id %d task %s part %d",
302 gang()->name(), id(), data.task()->name(), part);
303 }
304 assert(data.task() != NULL, "Got null task");
305 data.task()->work(part);
306 {
307 if (TraceWorkGang) {
308 tty->print("Finish for work gang %s id %d task %s part %d",
309 gang()->name(), id(), data.task()->name(), part);
310 }
311 // Grab the gang mutex.
312 MutexLocker ml(gang_monitor);
313 gang()->internal_note_finish();
314 // Tell the gang you are done.
315 gang_monitor->notify_all();
316 // Drop the gang mutex.
317 }
318 previous_sequence_number = data.sequence_number();
319 }
320 }
321
322 bool GangWorker::is_GC_task_thread() const {
323 return gang()->are_GC_task_threads();
324 }
325
326 bool GangWorker::is_ConcurrentGC_thread() const {
327 return gang()->are_ConcurrentGC_threads();
328 }
329
330 void GangWorker::print_on(outputStream* st) const {
331 st->print("\"%s\" ", name());
332 Thread::print_on(st);
333 st->cr();
334 }
335
336 // Printing methods
337
338 const char* AbstractWorkGang::name() const {
339 return _name;
340 }
341
342 #ifndef PRODUCT
343
344 const char* AbstractGangTask::name() const {
345 return _name;
346 }
347
348 #endif /* PRODUCT */
349
350 // *** WorkGangBarrierSync
351
352 WorkGangBarrierSync::WorkGangBarrierSync()
353 : _monitor(Mutex::safepoint, "work gang barrier sync", true),
354 _n_workers(0), _n_completed(0), _should_reset(false) {
355 }
356
357 WorkGangBarrierSync::WorkGangBarrierSync(int n_workers, const char* name)
358 : _monitor(Mutex::safepoint, name, true),
359 _n_workers(n_workers), _n_completed(0), _should_reset(false) {
360 }
361
362 void WorkGangBarrierSync::set_n_workers(int n_workers) {
363 _n_workers = n_workers;
364 _n_completed = 0;
365 _should_reset = false;
366 }
367
368 void WorkGangBarrierSync::enter() {
369 MutexLockerEx x(monitor(), Mutex::_no_safepoint_check_flag);
370 if (should_reset()) {
371 // The should_reset() was set and we are the first worker to enter
372 // the sync barrier. We will zero the n_completed() count which
373 // effectively resets the barrier.
374 zero_completed();
375 set_should_reset(false);
376 }
377 inc_completed();
378 if (n_completed() == n_workers()) {
379 // At this point we would like to reset the barrier to be ready in
380 // case it is used again. However, we cannot set n_completed() to
381 // 0, even after the notify_all(), given that some other workers
382 // might still be waiting for n_completed() to become ==
383 // n_workers(). So, if we set n_completed() to 0, those workers
384 // will get stuck (as they will wake up, see that n_completed() !=
385 // n_workers() and go back to sleep). Instead, we raise the
386 // should_reset() flag and the barrier will be reset the first
387 // time a worker enters it again.
388 set_should_reset(true);
389 monitor()->notify_all();
390 } else {
391 while (n_completed() != n_workers()) {
392 monitor()->wait(/* no_safepoint_check */ true);
393 }
394 }
395 }
396
397 // SubTasksDone functions.
398
399 SubTasksDone::SubTasksDone(int n) :
400 _n_tasks(n), _n_threads(1), _tasks(NULL) {
401 _tasks = NEW_C_HEAP_ARRAY(jint, n);
402 guarantee(_tasks != NULL, "alloc failure");
403 clear();
404 }
405
406 bool SubTasksDone::valid() {
407 return _tasks != NULL;
408 }
409
410 void SubTasksDone::set_n_threads(int t) {
411 #ifdef ASSERT
412 assert(_claimed == 0 || _threads_completed == _n_threads,
413 "should not be called while tasks are being processed!");
414 #endif
415 _n_threads = (t == 0 ? 1 : t);
416 }
417
418 void SubTasksDone::clear() {
419 for (int i = 0; i < _n_tasks; i++) {
420 _tasks[i] = 0;
421 }
422 _threads_completed = 0;
423 #ifdef ASSERT
424 _claimed = 0;
425 #endif
426 }
427
428 bool SubTasksDone::is_task_claimed(int t) {
429 assert(0 <= t && t < _n_tasks, "bad task id.");
430 jint old = _tasks[t];
431 if (old == 0) {
432 old = Atomic::cmpxchg(1, &_tasks[t], 0);
433 }
434 assert(_tasks[t] == 1, "What else?");
435 bool res = old != 0;
436 #ifdef ASSERT
437 if (!res) {
438 assert(_claimed < _n_tasks, "Too many tasks claimed; missing clear?");
439 Atomic::inc(&_claimed);
440 }
441 #endif
442 return res;
443 }
444
445 void SubTasksDone::all_tasks_completed() {
446 jint observed = _threads_completed;
447 jint old;
448 do {
449 old = observed;
450 observed = Atomic::cmpxchg(old+1, &_threads_completed, old);
451 } while (observed != old);
452 // If this was the last thread checking in, clear the tasks.
453 if (observed+1 == _n_threads) clear();
454 }
455
456
457 SubTasksDone::~SubTasksDone() {
458 if (_tasks != NULL) FREE_C_HEAP_ARRAY(jint, _tasks);
459 }
460
461 // *** SequentialSubTasksDone
462
463 void SequentialSubTasksDone::clear() {
464 _n_tasks = _n_claimed = 0;
465 _n_threads = _n_completed = 0;
466 }
467
468 bool SequentialSubTasksDone::valid() {
469 return _n_threads > 0;
470 }
471
472 bool SequentialSubTasksDone::is_task_claimed(int& t) {
473 jint* n_claimed_ptr = &_n_claimed;
474 t = *n_claimed_ptr;
475 while (t < _n_tasks) {
476 jint res = Atomic::cmpxchg(t+1, n_claimed_ptr, t);
477 if (res == t) {
478 return false;
479 }
480 t = *n_claimed_ptr;
481 }
482 return true;
483 }
484
485 bool SequentialSubTasksDone::all_tasks_completed() {
486 jint* n_completed_ptr = &_n_completed;
487 jint complete = *n_completed_ptr;
488 while (true) {
489 jint res = Atomic::cmpxchg(complete+1, n_completed_ptr, complete);
490 if (res == complete) {
491 break;
492 }
493 complete = res;
494 }
495 if (complete+1 == _n_threads) {
496 clear();
497 return true;
498 }
499 return false;
500 }
501
502 bool FreeIdSet::_stat_init = false;
503 FreeIdSet* FreeIdSet::_sets[NSets];
504 bool FreeIdSet::_safepoint;
505
506 FreeIdSet::FreeIdSet(int sz, Monitor* mon) :
507 _sz(sz), _mon(mon), _hd(0), _waiters(0), _index(-1), _claimed(0)
508 {
509 _ids = new int[sz];
510 for (int i = 0; i < sz; i++) _ids[i] = i+1;
511 _ids[sz-1] = end_of_list; // end of list.
512 if (_stat_init) {
513 for (int j = 0; j < NSets; j++) _sets[j] = NULL;
514 _stat_init = true;
515 }
516 // Add to sets. (This should happen while the system is still single-threaded.)
517 for (int j = 0; j < NSets; j++) {
518 if (_sets[j] == NULL) {
519 _sets[j] = this;
520 _index = j;
521 break;
522 }
523 }
524 guarantee(_index != -1, "Too many FreeIdSets in use!");
525 }
526
527 FreeIdSet::~FreeIdSet() {
528 _sets[_index] = NULL;
529 }
530
531 void FreeIdSet::set_safepoint(bool b) {
532 _safepoint = b;
533 if (b) {
534 for (int j = 0; j < NSets; j++) {
535 if (_sets[j] != NULL && _sets[j]->_waiters > 0) {
536 Monitor* mon = _sets[j]->_mon;
537 mon->lock_without_safepoint_check();
538 mon->notify_all();
539 mon->unlock();
540 }
541 }
542 }
543 }
544
545 #define FID_STATS 0
546
547 int FreeIdSet::claim_par_id() {
548 #if FID_STATS
549 thread_t tslf = thr_self();
550 tty->print("claim_par_id[%d]: sz = %d, claimed = %d\n", tslf, _sz, _claimed);
551 #endif
552 MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);
553 while (!_safepoint && _hd == end_of_list) {
554 _waiters++;
555 #if FID_STATS
556 if (_waiters > 5) {
557 tty->print("claim_par_id waiting[%d]: %d waiters, %d claimed.\n",
558 tslf, _waiters, _claimed);
559 }
560 #endif
561 _mon->wait(Mutex::_no_safepoint_check_flag);
562 _waiters--;
563 }
564 if (_hd == end_of_list) {
565 #if FID_STATS
566 tty->print("claim_par_id[%d]: returning EOL.\n", tslf);
567 #endif
568 return -1;
569 } else {
570 int res = _hd;
571 _hd = _ids[res];
572 _ids[res] = claimed; // For debugging.
573 _claimed++;
574 #if FID_STATS
575 tty->print("claim_par_id[%d]: returning %d, claimed = %d.\n",
576 tslf, res, _claimed);
577 #endif
578 return res;
579 }
580 }
581
582 bool FreeIdSet::claim_perm_id(int i) {
583 assert(0 <= i && i < _sz, "Out of range.");
584 MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);
585 int prev = end_of_list;
586 int cur = _hd;
587 while (cur != end_of_list) {
588 if (cur == i) {
589 if (prev == end_of_list) {
590 _hd = _ids[cur];
591 } else {
592 _ids[prev] = _ids[cur];
593 }
594 _ids[cur] = claimed;
595 _claimed++;
596 return true;
597 } else {
598 prev = cur;
599 cur = _ids[cur];
600 }
601 }
602 return false;
603
604 }
605
606 void FreeIdSet::release_par_id(int id) {
607 MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);
608 assert(_ids[id] == claimed, "Precondition.");
609 _ids[id] = _hd;
610 _hd = id;
611 _claimed--;
612 #if FID_STATS
613 tty->print("[%d] release_par_id(%d), waiters =%d, claimed = %d.\n",
614 thr_self(), id, _waiters, _claimed);
615 #endif
616 if (_waiters > 0)
617 // Notify all would be safer, but this is OK, right?
618 _mon->notify_all();
619 }