1 /*
2 * Copyright (c) 2001, 2012, 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, "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, "Cannot create worker GC thread. Out of system resources.");
97 return false;
98 }
99 if (!DisableStartThread) {
100 os::start_thread(new_worker);
101 }
102 }
103 return true;
104 }
105
106 AbstractWorkGang::~AbstractWorkGang() {
107 if (TraceWorkGang) {
108 tty->print_cr("Destructing work gang %s", name());
109 }
110 stop(); // stop all the workers
111 for (uint worker = 0; worker < total_workers(); worker += 1) {
112 delete gang_worker(worker);
113 }
114 delete gang_workers();
115 delete monitor();
116 }
117
118 GangWorker* AbstractWorkGang::gang_worker(uint i) const {
119 // Array index bounds checking.
120 GangWorker* result = NULL;
121 assert(gang_workers() != NULL, "No workers for indexing");
122 assert(((i >= 0) && (i < total_workers())), "Worker index out of bounds");
123 result = _gang_workers[i];
124 assert(result != NULL, "Indexing to null worker");
125 return result;
126 }
127
128 void WorkGang::run_task(AbstractGangTask* task) {
129 run_task(task, total_workers());
130 }
131
132 void WorkGang::run_task(AbstractGangTask* task, uint no_of_parallel_workers) {
133 task->set_for_termination(no_of_parallel_workers);
134
135 // This thread is executed by the VM thread which does not block
136 // on ordinary MutexLocker's.
137 MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag);
138 if (TraceWorkGang) {
139 tty->print_cr("Running work gang %s task %s", name(), task->name());
140 }
141 // Tell all the workers to run a task.
142 assert(task != NULL, "Running a null task");
143 // Initialize.
144 _task = task;
145 _sequence_number += 1;
146 _started_workers = 0;
147 _finished_workers = 0;
148 // Tell the workers to get to work.
149 monitor()->notify_all();
150 // Wait for them to be finished
151 while (finished_workers() < no_of_parallel_workers) {
152 if (TraceWorkGang) {
153 tty->print_cr("Waiting in work gang %s: %d/%d finished sequence %d",
154 name(), finished_workers(), no_of_parallel_workers,
155 _sequence_number);
156 }
157 monitor()->wait(/* no_safepoint_check */ true);
158 }
159 _task = NULL;
160 if (TraceWorkGang) {
161 tty->print_cr("\nFinished work gang %s: %d/%d sequence %d",
162 name(), finished_workers(), no_of_parallel_workers,
163 _sequence_number);
164 Thread* me = Thread::current();
165 tty->print_cr(" T: 0x%x VM_thread: %d", me, me->is_VM_thread());
166 }
167 }
168
169 void FlexibleWorkGang::run_task(AbstractGangTask* task) {
170 // If active_workers() is passed, _finished_workers
171 // must only be incremented for workers that find non_null
172 // work (as opposed to all those that just check that the
173 // task is not null).
174 WorkGang::run_task(task, (uint) active_workers());
175 }
176
177 void AbstractWorkGang::stop() {
178 // Tell all workers to terminate, then wait for them to become inactive.
179 MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag);
180 if (TraceWorkGang) {
181 tty->print_cr("Stopping work gang %s task %s", name(), task()->name());
182 }
183 _task = NULL;
184 _terminate = true;
185 monitor()->notify_all();
186 while (finished_workers() < active_workers()) {
187 if (TraceWorkGang) {
188 tty->print_cr("Waiting in work gang %s: %d/%d finished",
189 name(), finished_workers(), active_workers());
190 }
191 monitor()->wait(/* no_safepoint_check */ true);
192 }
193 }
194
195 void AbstractWorkGang::internal_worker_poll(WorkData* data) const {
196 assert(monitor()->owned_by_self(), "worker_poll is an internal method");
197 assert(data != NULL, "worker data is null");
198 data->set_terminate(terminate());
199 data->set_task(task());
200 data->set_sequence_number(sequence_number());
201 }
202
203 void AbstractWorkGang::internal_note_start() {
204 assert(monitor()->owned_by_self(), "note_finish is an internal method");
205 _started_workers += 1;
206 }
207
208 void AbstractWorkGang::internal_note_finish() {
209 assert(monitor()->owned_by_self(), "note_finish is an internal method");
210 _finished_workers += 1;
211 }
212
213 void AbstractWorkGang::print_worker_threads_on(outputStream* st) const {
214 uint num_thr = total_workers();
215 for (uint i = 0; i < num_thr; i++) {
216 gang_worker(i)->print_on(st);
217 st->cr();
218 }
219 }
220
221 void AbstractWorkGang::threads_do(ThreadClosure* tc) const {
222 assert(tc != NULL, "Null ThreadClosure");
223 uint num_thr = total_workers();
224 for (uint i = 0; i < num_thr; i++) {
225 tc->do_thread(gang_worker(i));
226 }
227 }
228
229 // GangWorker methods.
230
231 GangWorker::GangWorker(AbstractWorkGang* gang, uint id) {
232 _gang = gang;
233 set_id(id);
234 set_name("Gang worker#%d (%s)", id, gang->name());
235 }
236
237 void GangWorker::run() {
238 initialize();
239 loop();
240 }
241
242 void GangWorker::initialize() {
243 this->initialize_thread_local_storage();
244 this->record_stack_base_and_size();
245 assert(_gang != NULL, "No gang to run in");
246 os::set_priority(this, NearMaxPriority);
247 if (TraceWorkGang) {
248 tty->print_cr("Running gang worker for gang %s id %d",
249 gang()->name(), id());
250 }
251 // The VM thread should not execute here because MutexLocker's are used
252 // as (opposed to MutexLockerEx's).
253 assert(!Thread::current()->is_VM_thread(), "VM thread should not be part"
254 " of a work gang");
255 }
256
257 void GangWorker::loop() {
258 int previous_sequence_number = 0;
259 Monitor* gang_monitor = gang()->monitor();
260 for ( ; /* !terminate() */; ) {
261 WorkData data;
262 int part; // Initialized below.
263 {
264 // Grab the gang mutex.
265 MutexLocker ml(gang_monitor);
266 // Wait for something to do.
267 // Polling outside the while { wait } avoids missed notifies
268 // in the outer loop.
269 gang()->internal_worker_poll(&data);
270 if (TraceWorkGang) {
271 tty->print("Polled outside for work in gang %s worker %d",
272 gang()->name(), id());
273 tty->print(" terminate: %s",
274 data.terminate() ? "true" : "false");
275 tty->print(" sequence: %d (prev: %d)",
276 data.sequence_number(), previous_sequence_number);
277 if (data.task() != NULL) {
278 tty->print(" task: %s", data.task()->name());
279 } else {
280 tty->print(" task: NULL");
281 }
282 tty->cr();
283 }
284 for ( ; /* break or return */; ) {
285 // Terminate if requested.
286 if (data.terminate()) {
287 gang()->internal_note_finish();
288 gang_monitor->notify_all();
289 return;
290 }
291 // Check for new work.
292 if ((data.task() != NULL) &&
293 (data.sequence_number() != previous_sequence_number)) {
294 if (gang()->needs_more_workers()) {
295 gang()->internal_note_start();
296 gang_monitor->notify_all();
297 part = gang()->started_workers() - 1;
298 break;
299 }
300 }
301 // Nothing to do.
302 gang_monitor->wait(/* no_safepoint_check */ true);
303 gang()->internal_worker_poll(&data);
304 if (TraceWorkGang) {
305 tty->print("Polled inside for work in gang %s worker %d",
306 gang()->name(), id());
307 tty->print(" terminate: %s",
308 data.terminate() ? "true" : "false");
309 tty->print(" sequence: %d (prev: %d)",
310 data.sequence_number(), previous_sequence_number);
311 if (data.task() != NULL) {
312 tty->print(" task: %s", data.task()->name());
313 } else {
314 tty->print(" task: NULL");
315 }
316 tty->cr();
317 }
318 }
319 // Drop gang mutex.
320 }
321 if (TraceWorkGang) {
322 tty->print("Work for work gang %s id %d task %s part %d",
323 gang()->name(), id(), data.task()->name(), part);
324 }
325 assert(data.task() != NULL, "Got null task");
326 data.task()->work(part);
327 {
328 if (TraceWorkGang) {
329 tty->print("Finish for work gang %s id %d task %s part %d",
330 gang()->name(), id(), data.task()->name(), part);
331 }
332 // Grab the gang mutex.
333 MutexLocker ml(gang_monitor);
334 gang()->internal_note_finish();
335 // Tell the gang you are done.
336 gang_monitor->notify_all();
337 // Drop the gang mutex.
338 }
339 previous_sequence_number = data.sequence_number();
340 }
341 }
342
343 bool GangWorker::is_GC_task_thread() const {
344 return gang()->are_GC_task_threads();
345 }
346
347 bool GangWorker::is_ConcurrentGC_thread() const {
348 return gang()->are_ConcurrentGC_threads();
349 }
350
351 void GangWorker::print_on(outputStream* st) const {
352 st->print("\"%s\" ", name());
353 Thread::print_on(st);
354 st->cr();
355 }
356
357 // Printing methods
358
359 const char* AbstractWorkGang::name() const {
360 return _name;
361 }
362
363 #ifndef PRODUCT
364
365 const char* AbstractGangTask::name() const {
366 return _name;
367 }
368
369 #endif /* PRODUCT */
370
371 // FlexibleWorkGang
372
373
374 // *** WorkGangBarrierSync
375
376 WorkGangBarrierSync::WorkGangBarrierSync()
377 : _monitor(Mutex::safepoint, "work gang barrier sync", true),
378 _n_workers(0), _n_completed(0), _should_reset(false) {
379 }
380
381 WorkGangBarrierSync::WorkGangBarrierSync(uint n_workers, const char* name)
382 : _monitor(Mutex::safepoint, name, true),
383 _n_workers(n_workers), _n_completed(0), _should_reset(false) {
384 }
385
386 void WorkGangBarrierSync::set_n_workers(uint n_workers) {
387 _n_workers = n_workers;
388 _n_completed = 0;
389 _should_reset = false;
390 }
391
392 void WorkGangBarrierSync::enter() {
393 MutexLockerEx x(monitor(), Mutex::_no_safepoint_check_flag);
394 if (should_reset()) {
395 // The should_reset() was set and we are the first worker to enter
396 // the sync barrier. We will zero the n_completed() count which
397 // effectively resets the barrier.
398 zero_completed();
399 set_should_reset(false);
400 }
401 inc_completed();
402 if (n_completed() == n_workers()) {
403 // At this point we would like to reset the barrier to be ready in
404 // case it is used again. However, we cannot set n_completed() to
405 // 0, even after the notify_all(), given that some other workers
406 // might still be waiting for n_completed() to become ==
407 // n_workers(). So, if we set n_completed() to 0, those workers
408 // will get stuck (as they will wake up, see that n_completed() !=
409 // n_workers() and go back to sleep). Instead, we raise the
410 // should_reset() flag and the barrier will be reset the first
411 // time a worker enters it again.
412 set_should_reset(true);
413 monitor()->notify_all();
414 } else {
415 while (n_completed() != n_workers()) {
416 monitor()->wait(/* no_safepoint_check */ true);
417 }
418 }
419 }
420
421 // SubTasksDone functions.
422
423 SubTasksDone::SubTasksDone(uint n) :
424 _n_tasks(n), _n_threads(1), _tasks(NULL) {
425 _tasks = NEW_C_HEAP_ARRAY(uint, n, mtInternal);
426 guarantee(_tasks != NULL, "alloc failure");
427 clear();
428 }
429
430 bool SubTasksDone::valid() {
431 return _tasks != NULL;
432 }
433
434 void SubTasksDone::set_n_threads(uint t) {
435 assert(_claimed == 0 || _threads_completed == _n_threads,
436 "should not be called while tasks are being processed!");
437 _n_threads = (t == 0 ? 1 : t);
438 }
439
440 void SubTasksDone::clear() {
441 for (uint i = 0; i < _n_tasks; i++) {
442 _tasks[i] = 0;
443 }
444 _threads_completed = 0;
445 #ifdef ASSERT
446 _claimed = 0;
447 #endif
448 }
449
450 bool SubTasksDone::is_task_claimed(uint t) {
451 assert(0 <= t && t < _n_tasks, "bad task id.");
452 uint old = _tasks[t];
453 if (old == 0) {
454 old = Atomic::cmpxchg(1, &_tasks[t], 0);
455 }
456 assert(_tasks[t] == 1, "What else?");
457 bool res = old != 0;
458 #ifdef ASSERT
459 if (!res) {
460 assert(_claimed < _n_tasks, "Too many tasks claimed; missing clear?");
461 Atomic::inc((volatile jint*) &_claimed);
462 }
463 #endif
464 return res;
465 }
466
467 void SubTasksDone::all_tasks_completed() {
468 jint observed = _threads_completed;
469 jint old;
470 do {
471 old = observed;
472 observed = Atomic::cmpxchg(old+1, &_threads_completed, old);
473 } while (observed != old);
474 // If this was the last thread checking in, clear the tasks.
475 if (observed+1 == (jint)_n_threads) clear();
476 }
477
478
479 SubTasksDone::~SubTasksDone() {
480 if (_tasks != NULL) FREE_C_HEAP_ARRAY(jint, _tasks, mtInternal);
481 }
482
483 // *** SequentialSubTasksDone
484
485 void SequentialSubTasksDone::clear() {
486 _n_tasks = _n_claimed = 0;
487 _n_threads = _n_completed = 0;
488 }
489
490 bool SequentialSubTasksDone::valid() {
491 return _n_threads > 0;
492 }
493
494 bool SequentialSubTasksDone::is_task_claimed(uint& t) {
495 uint* n_claimed_ptr = &_n_claimed;
496 t = *n_claimed_ptr;
497 while (t < _n_tasks) {
498 jint res = Atomic::cmpxchg(t+1, n_claimed_ptr, t);
499 if (res == (jint)t) {
500 return false;
501 }
502 t = *n_claimed_ptr;
503 }
504 return true;
505 }
506
507 bool SequentialSubTasksDone::all_tasks_completed() {
508 uint* n_completed_ptr = &_n_completed;
509 uint complete = *n_completed_ptr;
510 while (true) {
511 uint res = Atomic::cmpxchg(complete+1, n_completed_ptr, complete);
512 if (res == complete) {
513 break;
514 }
515 complete = res;
516 }
517 if (complete+1 == _n_threads) {
518 clear();
519 return true;
520 }
521 return false;
522 }
523
524 bool FreeIdSet::_stat_init = false;
525 FreeIdSet* FreeIdSet::_sets[NSets];
526 bool FreeIdSet::_safepoint;
527
528 FreeIdSet::FreeIdSet(int sz, Monitor* mon) :
529 _sz(sz), _mon(mon), _hd(0), _waiters(0), _index(-1), _claimed(0)
530 {
531 _ids = new int[sz];
532 for (int i = 0; i < sz; i++) _ids[i] = i+1;
533 _ids[sz-1] = end_of_list; // end of list.
534 if (_stat_init) {
535 for (int j = 0; j < NSets; j++) _sets[j] = NULL;
536 _stat_init = true;
537 }
538 // Add to sets. (This should happen while the system is still single-threaded.)
539 for (int j = 0; j < NSets; j++) {
540 if (_sets[j] == NULL) {
541 _sets[j] = this;
542 _index = j;
543 break;
544 }
545 }
546 guarantee(_index != -1, "Too many FreeIdSets in use!");
547 }
548
549 FreeIdSet::~FreeIdSet() {
550 _sets[_index] = NULL;
551 }
552
553 void FreeIdSet::set_safepoint(bool b) {
554 _safepoint = b;
555 if (b) {
556 for (int j = 0; j < NSets; j++) {
557 if (_sets[j] != NULL && _sets[j]->_waiters > 0) {
558 Monitor* mon = _sets[j]->_mon;
559 mon->lock_without_safepoint_check();
560 mon->notify_all();
561 mon->unlock();
562 }
563 }
564 }
565 }
566
567 #define FID_STATS 0
568
569 int FreeIdSet::claim_par_id() {
570 #if FID_STATS
571 thread_t tslf = thr_self();
572 tty->print("claim_par_id[%d]: sz = %d, claimed = %d\n", tslf, _sz, _claimed);
573 #endif
574 MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);
575 while (!_safepoint && _hd == end_of_list) {
576 _waiters++;
577 #if FID_STATS
578 if (_waiters > 5) {
579 tty->print("claim_par_id waiting[%d]: %d waiters, %d claimed.\n",
580 tslf, _waiters, _claimed);
581 }
582 #endif
583 _mon->wait(Mutex::_no_safepoint_check_flag);
584 _waiters--;
585 }
586 if (_hd == end_of_list) {
587 #if FID_STATS
588 tty->print("claim_par_id[%d]: returning EOL.\n", tslf);
589 #endif
590 return -1;
591 } else {
592 int res = _hd;
593 _hd = _ids[res];
594 _ids[res] = claimed; // For debugging.
595 _claimed++;
596 #if FID_STATS
597 tty->print("claim_par_id[%d]: returning %d, claimed = %d.\n",
598 tslf, res, _claimed);
599 #endif
600 return res;
601 }
602 }
603
604 bool FreeIdSet::claim_perm_id(int i) {
605 assert(0 <= i && i < _sz, "Out of range.");
606 MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);
607 int prev = end_of_list;
608 int cur = _hd;
609 while (cur != end_of_list) {
610 if (cur == i) {
611 if (prev == end_of_list) {
612 _hd = _ids[cur];
613 } else {
614 _ids[prev] = _ids[cur];
615 }
616 _ids[cur] = claimed;
617 _claimed++;
618 return true;
619 } else {
620 prev = cur;
621 cur = _ids[cur];
622 }
623 }
624 return false;
625
626 }
627
628 void FreeIdSet::release_par_id(int id) {
629 MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);
630 assert(_ids[id] == claimed, "Precondition.");
631 _ids[id] = _hd;
632 _hd = id;
633 _claimed--;
634 #if FID_STATS
635 tty->print("[%d] release_par_id(%d), waiters =%d, claimed = %d.\n",
636 thr_self(), id, _waiters, _claimed);
637 #endif
638 if (_waiters > 0)
639 // Notify all would be safer, but this is OK, right?
640 _mon->notify_all();
641 }