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