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 "gc/shared/workgroup.hpp"
27 #include "memory/allocation.hpp"
28 #include "memory/allocation.inline.hpp"
29 #include "runtime/atomic.inline.hpp"
30 #include "runtime/os.hpp"
31
32 // Definitions of WorkGang methods.
33
34 AbstractWorkGang::AbstractWorkGang(const char* name,
35 bool are_GC_task_threads,
36 bool are_ConcurrentGC_threads) :
37 _name(name),
38 _are_GC_task_threads(are_GC_task_threads),
39 _are_ConcurrentGC_threads(are_ConcurrentGC_threads) {
40
41 assert(!(are_GC_task_threads && are_ConcurrentGC_threads),
42 "They cannot both be STW GC and Concurrent threads" );
43
44 // Other initialization.
45 _monitor = new Monitor(/* priority */ Mutex::leaf,
46 /* name */ "WorkGroup monitor",
47 /* allow_vm_block */ are_GC_task_threads,
48 Monitor::_safepoint_check_sometimes);
49 assert(monitor() != NULL, "Failed to allocate monitor");
50 _task = NULL;
51 _sequence_number = 0;
52 _started_workers = 0;
53 _finished_workers = 0;
54 }
55
56 WorkGang::WorkGang(const char* name,
57 uint workers,
58 bool are_GC_task_threads,
59 bool are_ConcurrentGC_threads) :
60 AbstractWorkGang(name, are_GC_task_threads, are_ConcurrentGC_threads) {
61 _total_workers = workers;
62 }
63
64 GangWorker* WorkGang::allocate_worker(uint which) {
65 GangWorker* new_worker = new GangWorker(this, which);
66 return new_worker;
67 }
68
69 // The current implementation will exit if the allocation
70 // of any worker fails. Still, return a boolean so that
71 // a future implementation can possibly do a partial
72 // initialization of the workers and report such to the
73 // caller.
74 bool WorkGang::initialize_workers() {
75
76 if (TraceWorkGang) {
77 tty->print_cr("Constructing work gang %s with %d threads",
78 name(),
79 total_workers());
80 }
81 _gang_workers = NEW_C_HEAP_ARRAY(GangWorker*, total_workers(), mtInternal);
82 if (gang_workers() == NULL) {
83 vm_exit_out_of_memory(0, OOM_MALLOC_ERROR, "Cannot create GangWorker array.");
84 return false;
85 }
86 os::ThreadType worker_type;
87 if (are_ConcurrentGC_threads()) {
88 worker_type = os::cgc_thread;
89 } else {
90 worker_type = os::pgc_thread;
91 }
92 for (uint worker = 0; worker < total_workers(); worker += 1) {
93 GangWorker* new_worker = allocate_worker(worker);
94 assert(new_worker != NULL, "Failed to allocate GangWorker");
95 _gang_workers[worker] = new_worker;
96 if (new_worker == NULL || !os::create_thread(new_worker, worker_type)) {
97 vm_exit_out_of_memory(0, OOM_MALLOC_ERROR,
98 "Cannot create worker GC thread. Out of system resources.");
99 return false;
100 }
101 if (!DisableStartThread) {
102 os::start_thread(new_worker);
103 }
104 }
105 return true;
106 }
107
108 GangWorker* AbstractWorkGang::gang_worker(uint i) const {
109 // Array index bounds checking.
110 GangWorker* result = NULL;
111 assert(gang_workers() != NULL, "No workers for indexing");
112 assert(i < total_workers(), "Worker index out of bounds");
113 result = _gang_workers[i];
114 assert(result != NULL, "Indexing to null worker");
115 return result;
116 }
117
118 void WorkGang::run_task(AbstractGangTask* task) {
119 run_task(task, total_workers());
120 }
121
122 void WorkGang::run_task(AbstractGangTask* task, uint no_of_parallel_workers) {
123 // This thread is executed by the VM thread which does not block
124 // on ordinary MutexLocker's.
125 MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag);
126 if (TraceWorkGang) {
127 tty->print_cr("Running work gang %s task %s", name(), task->name());
128 }
129 // Tell all the workers to run a task.
130 assert(task != NULL, "Running a null task");
131 // Initialize.
132 _task = task;
133 _sequence_number += 1;
134 _started_workers = 0;
135 _finished_workers = 0;
136 // Tell the workers to get to work.
137 monitor()->notify_all();
138 // Wait for them to be finished
139 while (finished_workers() < no_of_parallel_workers) {
140 if (TraceWorkGang) {
141 tty->print_cr("Waiting in work gang %s: %u/%u finished sequence %d",
142 name(), finished_workers(), no_of_parallel_workers,
143 _sequence_number);
144 }
145 monitor()->wait(/* no_safepoint_check */ true);
146 }
147 _task = NULL;
148 if (TraceWorkGang) {
149 tty->print_cr("\nFinished work gang %s: %u/%u sequence %d",
150 name(), finished_workers(), no_of_parallel_workers,
151 _sequence_number);
152 Thread* me = Thread::current();
153 tty->print_cr(" T: " PTR_FORMAT " VM_thread: %d", p2i(me), me->is_VM_thread());
154 }
155 }
156
157 void FlexibleWorkGang::run_task(AbstractGangTask* task) {
158 // If active_workers() is passed, _finished_workers
159 // must only be incremented for workers that find non_null
160 // work (as opposed to all those that just check that the
161 // task is not null).
162 WorkGang::run_task(task, (uint) active_workers());
163 }
164
165 void AbstractWorkGang::internal_worker_poll(WorkData* data) const {
166 assert(monitor()->owned_by_self(), "worker_poll is an internal method");
167 assert(data != NULL, "worker data is null");
168 data->set_task(task());
169 data->set_sequence_number(sequence_number());
170 }
171
172 void AbstractWorkGang::internal_note_start() {
173 assert(monitor()->owned_by_self(), "note_finish is an internal method");
174 _started_workers += 1;
175 }
176
177 void AbstractWorkGang::internal_note_finish() {
178 assert(monitor()->owned_by_self(), "note_finish is an internal method");
179 _finished_workers += 1;
180 }
181
182 void AbstractWorkGang::print_worker_threads_on(outputStream* st) const {
183 uint num_thr = total_workers();
184 for (uint i = 0; i < num_thr; i++) {
185 gang_worker(i)->print_on(st);
186 st->cr();
187 }
188 }
189
190 void AbstractWorkGang::threads_do(ThreadClosure* tc) const {
191 assert(tc != NULL, "Null ThreadClosure");
192 uint num_thr = total_workers();
193 for (uint i = 0; i < num_thr; i++) {
194 tc->do_thread(gang_worker(i));
195 }
196 }
197
198 // GangWorker methods.
199
200 GangWorker::GangWorker(AbstractWorkGang* gang, uint id) {
201 _gang = gang;
202 set_id(id);
203 set_name("%s#%d", gang->name(), id);
204 }
205
206 void GangWorker::run() {
207 initialize();
208 loop();
209 }
210
211 void GangWorker::initialize() {
212 this->initialize_thread_local_storage();
213 this->record_stack_base_and_size();
214 this->initialize_named_thread();
215 assert(_gang != NULL, "No gang to run in");
216 os::set_priority(this, NearMaxPriority);
217 if (TraceWorkGang) {
218 tty->print_cr("Running gang worker for gang %s id %u",
219 gang()->name(), id());
220 }
221 // The VM thread should not execute here because MutexLocker's are used
222 // as (opposed to MutexLockerEx's).
223 assert(!Thread::current()->is_VM_thread(), "VM thread should not be part"
224 " of a work gang");
225 }
226
227 void GangWorker::loop() {
228 int previous_sequence_number = 0;
229 Monitor* gang_monitor = gang()->monitor();
230 for ( ; ; ) {
231 WorkData data;
232 int part; // Initialized below.
233 {
234 // Grab the gang mutex.
235 MutexLocker ml(gang_monitor);
236 // Wait for something to do.
237 // Polling outside the while { wait } avoids missed notifies
238 // in the outer loop.
239 gang()->internal_worker_poll(&data);
240 if (TraceWorkGang) {
241 tty->print("Polled outside for work in gang %s worker %u",
242 gang()->name(), id());
243 tty->print(" sequence: %d (prev: %d)",
244 data.sequence_number(), previous_sequence_number);
245 if (data.task() != NULL) {
246 tty->print(" task: %s", data.task()->name());
247 } else {
248 tty->print(" task: NULL");
249 }
250 tty->cr();
251 }
252 for ( ; /* break */; ) {
253 // Check for new work.
254 if ((data.task() != NULL) &&
255 (data.sequence_number() != previous_sequence_number)) {
256 if (gang()->needs_more_workers()) {
257 gang()->internal_note_start();
258 gang_monitor->notify_all();
259 part = gang()->started_workers() - 1;
260 break;
261 }
262 }
263 // Nothing to do.
264 gang_monitor->wait(/* no_safepoint_check */ true);
265 gang()->internal_worker_poll(&data);
266 if (TraceWorkGang) {
267 tty->print("Polled inside for work in gang %s worker %u",
268 gang()->name(), id());
269 tty->print(" sequence: %d (prev: %d)",
270 data.sequence_number(), previous_sequence_number);
271 if (data.task() != NULL) {
272 tty->print(" task: %s", data.task()->name());
273 } else {
274 tty->print(" task: NULL");
275 }
276 tty->cr();
277 }
278 }
279 // Drop gang mutex.
280 }
281 if (TraceWorkGang) {
282 tty->print("Work for work gang %s id %u task %s part %d",
283 gang()->name(), id(), data.task()->name(), part);
284 }
285 assert(data.task() != NULL, "Got null task");
286 data.task()->work(part);
287 {
288 if (TraceWorkGang) {
289 tty->print("Finish for work gang %s id %u task %s part %d",
290 gang()->name(), id(), data.task()->name(), part);
291 }
292 // Grab the gang mutex.
293 MutexLocker ml(gang_monitor);
294 gang()->internal_note_finish();
295 // Tell the gang you are done.
296 gang_monitor->notify_all();
297 // Drop the gang mutex.
298 }
299 previous_sequence_number = data.sequence_number();
300 }
301 }
302
303 bool GangWorker::is_GC_task_thread() const {
304 return gang()->are_GC_task_threads();
305 }
306
307 bool GangWorker::is_ConcurrentGC_thread() const {
308 return gang()->are_ConcurrentGC_threads();
309 }
310
311 void GangWorker::print_on(outputStream* st) const {
312 st->print("\"%s\" ", name());
313 Thread::print_on(st);
314 st->cr();
315 }
316
317 // Printing methods
318
319 const char* AbstractWorkGang::name() const {
320 return _name;
321 }
322
323 #ifndef PRODUCT
324
325 const char* AbstractGangTask::name() const {
326 return _name;
327 }
328
329 #endif /* PRODUCT */
330
331 // FlexibleWorkGang
332
333
334 // *** WorkGangBarrierSync
335
336 WorkGangBarrierSync::WorkGangBarrierSync()
337 : _monitor(Mutex::safepoint, "work gang barrier sync", true,
338 Monitor::_safepoint_check_never),
339 _n_workers(0), _n_completed(0), _should_reset(false), _aborted(false) {
340 }
341
342 WorkGangBarrierSync::WorkGangBarrierSync(uint n_workers, const char* name)
343 : _monitor(Mutex::safepoint, name, true, Monitor::_safepoint_check_never),
344 _n_workers(n_workers), _n_completed(0), _should_reset(false), _aborted(false) {
345 }
346
347 void WorkGangBarrierSync::set_n_workers(uint n_workers) {
348 _n_workers = n_workers;
349 _n_completed = 0;
350 _should_reset = false;
351 _aborted = false;
352 }
353
354 bool WorkGangBarrierSync::enter() {
355 MutexLockerEx x(monitor(), Mutex::_no_safepoint_check_flag);
356 if (should_reset()) {
357 // The should_reset() was set and we are the first worker to enter
358 // the sync barrier. We will zero the n_completed() count which
359 // effectively resets the barrier.
360 zero_completed();
361 set_should_reset(false);
362 }
363 inc_completed();
364 if (n_completed() == n_workers()) {
365 // At this point we would like to reset the barrier to be ready in
366 // case it is used again. However, we cannot set n_completed() to
367 // 0, even after the notify_all(), given that some other workers
368 // might still be waiting for n_completed() to become ==
369 // n_workers(). So, if we set n_completed() to 0, those workers
370 // will get stuck (as they will wake up, see that n_completed() !=
371 // n_workers() and go back to sleep). Instead, we raise the
372 // should_reset() flag and the barrier will be reset the first
373 // time a worker enters it again.
374 set_should_reset(true);
375 monitor()->notify_all();
376 } else {
377 while (n_completed() != n_workers() && !aborted()) {
378 monitor()->wait(/* no_safepoint_check */ true);
379 }
380 }
381 return !aborted();
382 }
383
384 void WorkGangBarrierSync::abort() {
385 MutexLockerEx x(monitor(), Mutex::_no_safepoint_check_flag);
386 set_aborted();
387 monitor()->notify_all();
388 }
389
390 // SubTasksDone functions.
391
392 SubTasksDone::SubTasksDone(uint n) :
393 _n_tasks(n), _tasks(NULL) {
394 _tasks = NEW_C_HEAP_ARRAY(uint, n, mtInternal);
395 guarantee(_tasks != NULL, "alloc failure");
396 clear();
397 }
398
399 bool SubTasksDone::valid() {
400 return _tasks != NULL;
401 }
402
403 void SubTasksDone::clear() {
404 for (uint i = 0; i < _n_tasks; i++) {
405 _tasks[i] = 0;
406 }
407 _threads_completed = 0;
408 #ifdef ASSERT
409 _claimed = 0;
410 #endif
411 }
412
413 bool SubTasksDone::is_task_claimed(uint t) {
414 assert(t < _n_tasks, "bad task id.");
415 uint old = _tasks[t];
416 if (old == 0) {
417 old = Atomic::cmpxchg(1, &_tasks[t], 0);
418 }
419 assert(_tasks[t] == 1, "What else?");
420 bool res = old != 0;
421 #ifdef ASSERT
422 if (!res) {
423 assert(_claimed < _n_tasks, "Too many tasks claimed; missing clear?");
424 Atomic::inc((volatile jint*) &_claimed);
425 }
426 #endif
427 return res;
428 }
429
430 void SubTasksDone::all_tasks_completed(uint n_threads) {
431 jint observed = _threads_completed;
432 jint old;
433 do {
434 old = observed;
435 observed = Atomic::cmpxchg(old+1, &_threads_completed, old);
436 } while (observed != old);
437 // If this was the last thread checking in, clear the tasks.
438 uint adjusted_thread_count = (n_threads == 0 ? 1 : n_threads);
439 if (observed + 1 == (jint)adjusted_thread_count) {
440 clear();
441 }
442 }
443
444
445 SubTasksDone::~SubTasksDone() {
446 if (_tasks != NULL) FREE_C_HEAP_ARRAY(jint, _tasks);
447 }
448
449 // *** SequentialSubTasksDone
450
451 void SequentialSubTasksDone::clear() {
452 _n_tasks = _n_claimed = 0;
453 _n_threads = _n_completed = 0;
454 }
455
456 bool SequentialSubTasksDone::valid() {
457 return _n_threads > 0;
458 }
459
460 bool SequentialSubTasksDone::is_task_claimed(uint& t) {
461 uint* n_claimed_ptr = &_n_claimed;
462 t = *n_claimed_ptr;
463 while (t < _n_tasks) {
464 jint res = Atomic::cmpxchg(t+1, n_claimed_ptr, t);
465 if (res == (jint)t) {
466 return false;
467 }
468 t = *n_claimed_ptr;
469 }
470 return true;
471 }
472
473 bool SequentialSubTasksDone::all_tasks_completed() {
474 uint* n_completed_ptr = &_n_completed;
475 uint complete = *n_completed_ptr;
476 while (true) {
477 uint res = Atomic::cmpxchg(complete+1, n_completed_ptr, complete);
478 if (res == complete) {
479 break;
480 }
481 complete = res;
482 }
483 if (complete+1 == _n_threads) {
484 clear();
485 return true;
486 }
487 return false;
488 }
489
490 bool FreeIdSet::_stat_init = false;
491 FreeIdSet* FreeIdSet::_sets[NSets];
492 bool FreeIdSet::_safepoint;
493
494 FreeIdSet::FreeIdSet(int sz, Monitor* mon) :
495 _sz(sz), _mon(mon), _hd(0), _waiters(0), _index(-1), _claimed(0)
496 {
497 _ids = NEW_C_HEAP_ARRAY(int, sz, mtInternal);
498 for (int i = 0; i < sz; i++) _ids[i] = i+1;
499 _ids[sz-1] = end_of_list; // end of list.
500 if (_stat_init) {
501 for (int j = 0; j < NSets; j++) _sets[j] = NULL;
502 _stat_init = true;
503 }
504 // Add to sets. (This should happen while the system is still single-threaded.)
505 for (int j = 0; j < NSets; j++) {
506 if (_sets[j] == NULL) {
507 _sets[j] = this;
508 _index = j;
509 break;
510 }
511 }
512 guarantee(_index != -1, "Too many FreeIdSets in use!");
513 }
514
515 FreeIdSet::~FreeIdSet() {
516 _sets[_index] = NULL;
517 FREE_C_HEAP_ARRAY(int, _ids);
518 }
519
520 void FreeIdSet::set_safepoint(bool b) {
521 _safepoint = b;
522 if (b) {
523 for (int j = 0; j < NSets; j++) {
524 if (_sets[j] != NULL && _sets[j]->_waiters > 0) {
525 Monitor* mon = _sets[j]->_mon;
526 mon->lock_without_safepoint_check();
527 mon->notify_all();
528 mon->unlock();
529 }
530 }
531 }
532 }
533
534 #define FID_STATS 0
535
536 int FreeIdSet::claim_par_id() {
537 #if FID_STATS
538 thread_t tslf = thr_self();
539 tty->print("claim_par_id[%d]: sz = %d, claimed = %d\n", tslf, _sz, _claimed);
540 #endif
541 MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);
542 while (!_safepoint && _hd == end_of_list) {
543 _waiters++;
544 #if FID_STATS
545 if (_waiters > 5) {
546 tty->print("claim_par_id waiting[%d]: %d waiters, %d claimed.\n",
547 tslf, _waiters, _claimed);
548 }
549 #endif
550 _mon->wait(Mutex::_no_safepoint_check_flag);
551 _waiters--;
552 }
553 if (_hd == end_of_list) {
554 #if FID_STATS
555 tty->print("claim_par_id[%d]: returning EOL.\n", tslf);
556 #endif
557 return -1;
558 } else {
559 int res = _hd;
560 _hd = _ids[res];
561 _ids[res] = claimed; // For debugging.
562 _claimed++;
563 #if FID_STATS
564 tty->print("claim_par_id[%d]: returning %d, claimed = %d.\n",
565 tslf, res, _claimed);
566 #endif
567 return res;
568 }
569 }
570
571 bool FreeIdSet::claim_perm_id(int i) {
572 assert(0 <= i && i < _sz, "Out of range.");
573 MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);
574 int prev = end_of_list;
575 int cur = _hd;
576 while (cur != end_of_list) {
577 if (cur == i) {
578 if (prev == end_of_list) {
579 _hd = _ids[cur];
580 } else {
581 _ids[prev] = _ids[cur];
582 }
583 _ids[cur] = claimed;
584 _claimed++;
585 return true;
586 } else {
587 prev = cur;
588 cur = _ids[cur];
589 }
590 }
591 return false;
592
593 }
594
595 void FreeIdSet::release_par_id(int id) {
596 MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);
597 assert(_ids[id] == claimed, "Precondition.");
598 _ids[id] = _hd;
599 _hd = id;
600 _claimed--;
601 #if FID_STATS
602 tty->print("[%d] release_par_id(%d), waiters =%d, claimed = %d.\n",
603 thr_self(), id, _waiters, _claimed);
604 #endif
605 if (_waiters > 0)
606 // Notify all would be safer, but this is OK, right?
607 _mon->notify_all();
608 }