Mercurial > hg > truffle
annotate src/share/vm/runtime/vmThread.cpp @ 1959:9eecf81a02fb
7000578: CMS: assert(SafepointSynchronize::is_at_safepoint()) failed: Else races are possible
Summary: Weakened assert in onj_is_alive() to allow its use at initialization time when is_at_safepoint() normally reports false; added some related asserts to check order of is_init_completed() after Universe::is_fully_initialized().
Reviewed-by: jcoomes
author | ysr |
---|---|
date | Tue, 16 Nov 2010 13:58:48 -0800 |
parents | c18cbe5936b8 |
children | f95d63e2154a |
rev | line source |
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0 | 1 /* |
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2 * Copyright (c) 1998, 2010, Oracle and/or its affiliates. All rights reserved. |
0 | 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 * | |
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
0 | 22 * |
23 */ | |
24 | |
25 # include "incls/_precompiled.incl" | |
26 # include "incls/_vmThread.cpp.incl" | |
27 | |
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28 HS_DTRACE_PROBE_DECL3(hotspot, vmops__request, char *, uintptr_t, int); |
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29 HS_DTRACE_PROBE_DECL3(hotspot, vmops__begin, char *, uintptr_t, int); |
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30 HS_DTRACE_PROBE_DECL3(hotspot, vmops__end, char *, uintptr_t, int); |
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31 |
0 | 32 // Dummy VM operation to act as first element in our circular double-linked list |
33 class VM_Dummy: public VM_Operation { | |
34 VMOp_Type type() const { return VMOp_Dummy; } | |
35 void doit() {}; | |
36 }; | |
37 | |
38 VMOperationQueue::VMOperationQueue() { | |
39 // The queue is a circular doubled-linked list, which always contains | |
40 // one element (i.e., one element means empty). | |
41 for(int i = 0; i < nof_priorities; i++) { | |
42 _queue_length[i] = 0; | |
43 _queue_counter = 0; | |
44 _queue[i] = new VM_Dummy(); | |
45 _queue[i]->set_next(_queue[i]); | |
46 _queue[i]->set_prev(_queue[i]); | |
47 } | |
48 _drain_list = NULL; | |
49 } | |
50 | |
51 | |
52 bool VMOperationQueue::queue_empty(int prio) { | |
53 // It is empty if there is exactly one element | |
54 bool empty = (_queue[prio] == _queue[prio]->next()); | |
55 assert( (_queue_length[prio] == 0 && empty) || | |
56 (_queue_length[prio] > 0 && !empty), "sanity check"); | |
57 return _queue_length[prio] == 0; | |
58 } | |
59 | |
60 // Inserts an element to the right of the q element | |
61 void VMOperationQueue::insert(VM_Operation* q, VM_Operation* n) { | |
62 assert(q->next()->prev() == q && q->prev()->next() == q, "sanity check"); | |
63 n->set_prev(q); | |
64 n->set_next(q->next()); | |
65 q->next()->set_prev(n); | |
66 q->set_next(n); | |
67 } | |
68 | |
69 void VMOperationQueue::queue_add_front(int prio, VM_Operation *op) { | |
70 _queue_length[prio]++; | |
71 insert(_queue[prio]->next(), op); | |
72 } | |
73 | |
74 void VMOperationQueue::queue_add_back(int prio, VM_Operation *op) { | |
75 _queue_length[prio]++; | |
76 insert(_queue[prio]->prev(), op); | |
77 } | |
78 | |
79 | |
80 void VMOperationQueue::unlink(VM_Operation* q) { | |
81 assert(q->next()->prev() == q && q->prev()->next() == q, "sanity check"); | |
82 q->prev()->set_next(q->next()); | |
83 q->next()->set_prev(q->prev()); | |
84 } | |
85 | |
86 VM_Operation* VMOperationQueue::queue_remove_front(int prio) { | |
87 if (queue_empty(prio)) return NULL; | |
88 assert(_queue_length[prio] >= 0, "sanity check"); | |
89 _queue_length[prio]--; | |
90 VM_Operation* r = _queue[prio]->next(); | |
91 assert(r != _queue[prio], "cannot remove base element"); | |
92 unlink(r); | |
93 return r; | |
94 } | |
95 | |
96 VM_Operation* VMOperationQueue::queue_drain(int prio) { | |
97 if (queue_empty(prio)) return NULL; | |
98 DEBUG_ONLY(int length = _queue_length[prio];); | |
99 assert(length >= 0, "sanity check"); | |
100 _queue_length[prio] = 0; | |
101 VM_Operation* r = _queue[prio]->next(); | |
102 assert(r != _queue[prio], "cannot remove base element"); | |
103 // remove links to base element from head and tail | |
104 r->set_prev(NULL); | |
105 _queue[prio]->prev()->set_next(NULL); | |
106 // restore queue to empty state | |
107 _queue[prio]->set_next(_queue[prio]); | |
108 _queue[prio]->set_prev(_queue[prio]); | |
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109 assert(queue_empty(prio), "drain corrupted queue"); |
0 | 110 #ifdef DEBUG |
111 int len = 0; | |
112 VM_Operation* cur; | |
113 for(cur = r; cur != NULL; cur=cur->next()) len++; | |
114 assert(len == length, "drain lost some ops"); | |
115 #endif | |
116 return r; | |
117 } | |
118 | |
119 void VMOperationQueue::queue_oops_do(int queue, OopClosure* f) { | |
120 VM_Operation* cur = _queue[queue]; | |
121 cur = cur->next(); | |
122 while (cur != _queue[queue]) { | |
123 cur->oops_do(f); | |
124 cur = cur->next(); | |
125 } | |
126 } | |
127 | |
128 void VMOperationQueue::drain_list_oops_do(OopClosure* f) { | |
129 VM_Operation* cur = _drain_list; | |
130 while (cur != NULL) { | |
131 cur->oops_do(f); | |
132 cur = cur->next(); | |
133 } | |
134 } | |
135 | |
136 //----------------------------------------------------------------- | |
137 // High-level interface | |
138 bool VMOperationQueue::add(VM_Operation *op) { | |
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139 |
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140 HS_DTRACE_PROBE3(hotspot, vmops__request, op->name(), strlen(op->name()), |
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141 op->evaluation_mode()); |
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142 |
0 | 143 // Encapsulates VM queue policy. Currently, that |
144 // only involves putting them on the right list | |
145 if (op->evaluate_at_safepoint()) { | |
146 queue_add_back(SafepointPriority, op); | |
147 return true; | |
148 } | |
149 | |
150 queue_add_back(MediumPriority, op); | |
151 return true; | |
152 } | |
153 | |
154 VM_Operation* VMOperationQueue::remove_next() { | |
155 // Assuming VMOperation queue is two-level priority queue. If there are | |
156 // more than two priorities, we need a different scheduling algorithm. | |
157 assert(SafepointPriority == 0 && MediumPriority == 1 && nof_priorities == 2, | |
158 "current algorithm does not work"); | |
159 | |
160 // simple counter based scheduling to prevent starvation of lower priority | |
161 // queue. -- see 4390175 | |
162 int high_prio, low_prio; | |
163 if (_queue_counter++ < 10) { | |
164 high_prio = SafepointPriority; | |
165 low_prio = MediumPriority; | |
166 } else { | |
167 _queue_counter = 0; | |
168 high_prio = MediumPriority; | |
169 low_prio = SafepointPriority; | |
170 } | |
171 | |
172 return queue_remove_front(queue_empty(high_prio) ? low_prio : high_prio); | |
173 } | |
174 | |
175 void VMOperationQueue::oops_do(OopClosure* f) { | |
176 for(int i = 0; i < nof_priorities; i++) { | |
177 queue_oops_do(i, f); | |
178 } | |
179 drain_list_oops_do(f); | |
180 } | |
181 | |
182 | |
183 //------------------------------------------------------------------------------------------------------------------ | |
184 // Implementation of VMThread stuff | |
185 | |
186 bool VMThread::_should_terminate = false; | |
187 bool VMThread::_terminated = false; | |
188 Monitor* VMThread::_terminate_lock = NULL; | |
189 VMThread* VMThread::_vm_thread = NULL; | |
190 VM_Operation* VMThread::_cur_vm_operation = NULL; | |
191 VMOperationQueue* VMThread::_vm_queue = NULL; | |
192 PerfCounter* VMThread::_perf_accumulated_vm_operation_time = NULL; | |
193 | |
194 | |
195 void VMThread::create() { | |
196 assert(vm_thread() == NULL, "we can only allocate one VMThread"); | |
197 _vm_thread = new VMThread(); | |
198 | |
199 // Create VM operation queue | |
200 _vm_queue = new VMOperationQueue(); | |
201 guarantee(_vm_queue != NULL, "just checking"); | |
202 | |
203 _terminate_lock = new Monitor(Mutex::safepoint, "VMThread::_terminate_lock", true); | |
204 | |
205 if (UsePerfData) { | |
206 // jvmstat performance counters | |
207 Thread* THREAD = Thread::current(); | |
208 _perf_accumulated_vm_operation_time = | |
209 PerfDataManager::create_counter(SUN_THREADS, "vmOperationTime", | |
210 PerfData::U_Ticks, CHECK); | |
211 } | |
212 } | |
213 | |
214 | |
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215 VMThread::VMThread() : NamedThread() { |
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216 set_name("VM Thread"); |
0 | 217 } |
218 | |
219 void VMThread::destroy() { | |
220 if (_vm_thread != NULL) { | |
221 delete _vm_thread; | |
222 _vm_thread = NULL; // VM thread is gone | |
223 } | |
224 } | |
225 | |
226 void VMThread::run() { | |
227 assert(this == vm_thread(), "check"); | |
228 | |
229 this->initialize_thread_local_storage(); | |
230 this->record_stack_base_and_size(); | |
231 // Notify_lock wait checks on active_handles() to rewait in | |
232 // case of spurious wakeup, it should wait on the last | |
233 // value set prior to the notify | |
234 this->set_active_handles(JNIHandleBlock::allocate_block()); | |
235 | |
236 { | |
237 MutexLocker ml(Notify_lock); | |
238 Notify_lock->notify(); | |
239 } | |
240 // Notify_lock is destroyed by Threads::create_vm() | |
241 | |
242 int prio = (VMThreadPriority == -1) | |
243 ? os::java_to_os_priority[NearMaxPriority] | |
244 : VMThreadPriority; | |
245 // Note that I cannot call os::set_priority because it expects Java | |
246 // priorities and I am *explicitly* using OS priorities so that it's | |
247 // possible to set the VM thread priority higher than any Java thread. | |
248 os::set_native_priority( this, prio ); | |
249 | |
250 // Wait for VM_Operations until termination | |
251 this->loop(); | |
252 | |
253 // Note the intention to exit before safepointing. | |
254 // 6295565 This has the effect of waiting for any large tty | |
255 // outputs to finish. | |
256 if (xtty != NULL) { | |
257 ttyLocker ttyl; | |
258 xtty->begin_elem("destroy_vm"); | |
259 xtty->stamp(); | |
260 xtty->end_elem(); | |
261 assert(should_terminate(), "termination flag must be set"); | |
262 } | |
263 | |
264 // 4526887 let VM thread exit at Safepoint | |
265 SafepointSynchronize::begin(); | |
266 | |
267 if (VerifyBeforeExit) { | |
268 HandleMark hm(VMThread::vm_thread()); | |
269 // Among other things, this ensures that Eden top is correct. | |
270 Universe::heap()->prepare_for_verify(); | |
271 os::check_heap(); | |
272 Universe::verify(true, true); // Silent verification to not polute normal output | |
273 } | |
274 | |
275 CompileBroker::set_should_block(); | |
276 | |
277 // wait for threads (compiler threads or daemon threads) in the | |
278 // _thread_in_native state to block. | |
279 VM_Exit::wait_for_threads_in_native_to_block(); | |
280 | |
281 // signal other threads that VM process is gone | |
282 { | |
283 // Note: we must have the _no_safepoint_check_flag. Mutex::lock() allows | |
284 // VM thread to enter any lock at Safepoint as long as its _owner is NULL. | |
285 // If that happens after _terminate_lock->wait() has unset _owner | |
286 // but before it actually drops the lock and waits, the notification below | |
287 // may get lost and we will have a hang. To avoid this, we need to use | |
288 // Mutex::lock_without_safepoint_check(). | |
289 MutexLockerEx ml(_terminate_lock, Mutex::_no_safepoint_check_flag); | |
290 _terminated = true; | |
291 _terminate_lock->notify(); | |
292 } | |
293 | |
294 // Deletion must be done synchronously by the JNI DestroyJavaVM thread | |
295 // so that the VMThread deletion completes before the main thread frees | |
296 // up the CodeHeap. | |
297 | |
298 } | |
299 | |
300 | |
301 // Notify the VMThread that the last non-daemon JavaThread has terminated, | |
302 // and wait until operation is performed. | |
303 void VMThread::wait_for_vm_thread_exit() { | |
304 { MutexLocker mu(VMOperationQueue_lock); | |
305 _should_terminate = true; | |
306 VMOperationQueue_lock->notify(); | |
307 } | |
308 | |
309 // Note: VM thread leaves at Safepoint. We are not stopped by Safepoint | |
310 // because this thread has been removed from the threads list. But anything | |
311 // that could get blocked by Safepoint should not be used after this point, | |
312 // otherwise we will hang, since there is no one can end the safepoint. | |
313 | |
314 // Wait until VM thread is terminated | |
315 // Note: it should be OK to use Terminator_lock here. But this is called | |
316 // at a very delicate time (VM shutdown) and we are operating in non- VM | |
317 // thread at Safepoint. It's safer to not share lock with other threads. | |
318 { MutexLockerEx ml(_terminate_lock, Mutex::_no_safepoint_check_flag); | |
319 while(!VMThread::is_terminated()) { | |
320 _terminate_lock->wait(Mutex::_no_safepoint_check_flag); | |
321 } | |
322 } | |
323 } | |
324 | |
325 void VMThread::print_on(outputStream* st) const { | |
326 st->print("\"%s\" ", name()); | |
327 Thread::print_on(st); | |
328 st->cr(); | |
329 } | |
330 | |
331 void VMThread::evaluate_operation(VM_Operation* op) { | |
332 ResourceMark rm; | |
333 | |
334 { | |
335 PerfTraceTime vm_op_timer(perf_accumulated_vm_operation_time()); | |
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336 HS_DTRACE_PROBE3(hotspot, vmops__begin, op->name(), strlen(op->name()), |
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337 op->evaluation_mode()); |
0 | 338 op->evaluate(); |
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339 HS_DTRACE_PROBE3(hotspot, vmops__end, op->name(), strlen(op->name()), |
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340 op->evaluation_mode()); |
0 | 341 } |
342 | |
343 // Last access of info in _cur_vm_operation! | |
344 bool c_heap_allocated = op->is_cheap_allocated(); | |
345 | |
346 // Mark as completed | |
347 if (!op->evaluate_concurrently()) { | |
348 op->calling_thread()->increment_vm_operation_completed_count(); | |
349 } | |
350 // It is unsafe to access the _cur_vm_operation after the 'increment_vm_operation_completed_count' call, | |
351 // since if it is stack allocated the calling thread might have deallocated | |
352 if (c_heap_allocated) { | |
353 delete _cur_vm_operation; | |
354 } | |
355 } | |
356 | |
357 | |
358 void VMThread::loop() { | |
359 assert(_cur_vm_operation == NULL, "no current one should be executing"); | |
360 | |
361 while(true) { | |
362 VM_Operation* safepoint_ops = NULL; | |
363 // | |
364 // Wait for VM operation | |
365 // | |
366 // use no_safepoint_check to get lock without attempting to "sneak" | |
367 { MutexLockerEx mu_queue(VMOperationQueue_lock, | |
368 Mutex::_no_safepoint_check_flag); | |
369 | |
370 // Look for new operation | |
371 assert(_cur_vm_operation == NULL, "no current one should be executing"); | |
372 _cur_vm_operation = _vm_queue->remove_next(); | |
373 | |
374 // Stall time tracking code | |
375 if (PrintVMQWaitTime && _cur_vm_operation != NULL && | |
376 !_cur_vm_operation->evaluate_concurrently()) { | |
377 long stall = os::javaTimeMillis() - _cur_vm_operation->timestamp(); | |
378 if (stall > 0) | |
379 tty->print_cr("%s stall: %Ld", _cur_vm_operation->name(), stall); | |
380 } | |
381 | |
382 while (!should_terminate() && _cur_vm_operation == NULL) { | |
383 // wait with a timeout to guarantee safepoints at regular intervals | |
384 bool timedout = | |
385 VMOperationQueue_lock->wait(Mutex::_no_safepoint_check_flag, | |
386 GuaranteedSafepointInterval); | |
387 | |
388 // Support for self destruction | |
389 if ((SelfDestructTimer != 0) && !is_error_reported() && | |
390 (os::elapsedTime() > SelfDestructTimer * 60)) { | |
391 tty->print_cr("VM self-destructed"); | |
392 exit(-1); | |
393 } | |
394 | |
395 if (timedout && (SafepointALot || | |
396 SafepointSynchronize::is_cleanup_needed())) { | |
397 MutexUnlockerEx mul(VMOperationQueue_lock, | |
398 Mutex::_no_safepoint_check_flag); | |
399 // Force a safepoint since we have not had one for at least | |
400 // 'GuaranteedSafepointInterval' milliseconds. This will run all | |
401 // the clean-up processing that needs to be done regularly at a | |
402 // safepoint | |
403 SafepointSynchronize::begin(); | |
404 #ifdef ASSERT | |
405 if (GCALotAtAllSafepoints) InterfaceSupport::check_gc_alot(); | |
406 #endif | |
407 SafepointSynchronize::end(); | |
408 } | |
409 _cur_vm_operation = _vm_queue->remove_next(); | |
410 | |
411 // If we are at a safepoint we will evaluate all the operations that | |
412 // follow that also require a safepoint | |
413 if (_cur_vm_operation != NULL && | |
414 _cur_vm_operation->evaluate_at_safepoint()) { | |
415 safepoint_ops = _vm_queue->drain_at_safepoint_priority(); | |
416 } | |
417 } | |
418 | |
419 if (should_terminate()) break; | |
420 } // Release mu_queue_lock | |
421 | |
422 // | |
423 // Execute VM operation | |
424 // | |
425 { HandleMark hm(VMThread::vm_thread()); | |
426 | |
427 EventMark em("Executing VM operation: %s", vm_operation()->name()); | |
428 assert(_cur_vm_operation != NULL, "we should have found an operation to execute"); | |
429 | |
430 // Give the VM thread an extra quantum. Jobs tend to be bursty and this | |
431 // helps the VM thread to finish up the job. | |
432 // FIXME: When this is enabled and there are many threads, this can degrade | |
433 // performance significantly. | |
434 if( VMThreadHintNoPreempt ) | |
435 os::hint_no_preempt(); | |
436 | |
437 // If we are at a safepoint we will evaluate all the operations that | |
438 // follow that also require a safepoint | |
439 if (_cur_vm_operation->evaluate_at_safepoint()) { | |
440 | |
441 _vm_queue->set_drain_list(safepoint_ops); // ensure ops can be scanned | |
442 | |
443 SafepointSynchronize::begin(); | |
444 evaluate_operation(_cur_vm_operation); | |
445 // now process all queued safepoint ops, iteratively draining | |
446 // the queue until there are none left | |
447 do { | |
448 _cur_vm_operation = safepoint_ops; | |
449 if (_cur_vm_operation != NULL) { | |
450 do { | |
451 // evaluate_operation deletes the op object so we have | |
452 // to grab the next op now | |
453 VM_Operation* next = _cur_vm_operation->next(); | |
454 _vm_queue->set_drain_list(next); | |
455 evaluate_operation(_cur_vm_operation); | |
456 _cur_vm_operation = next; | |
457 if (PrintSafepointStatistics) { | |
458 SafepointSynchronize::inc_vmop_coalesced_count(); | |
459 } | |
460 } while (_cur_vm_operation != NULL); | |
461 } | |
462 // There is a chance that a thread enqueued a safepoint op | |
463 // since we released the op-queue lock and initiated the safepoint. | |
464 // So we drain the queue again if there is anything there, as an | |
465 // optimization to try and reduce the number of safepoints. | |
466 // As the safepoint synchronizes us with JavaThreads we will see | |
467 // any enqueue made by a JavaThread, but the peek will not | |
468 // necessarily detect a concurrent enqueue by a GC thread, but | |
469 // that simply means the op will wait for the next major cycle of the | |
470 // VMThread - just as it would if the GC thread lost the race for | |
471 // the lock. | |
472 if (_vm_queue->peek_at_safepoint_priority()) { | |
473 // must hold lock while draining queue | |
474 MutexLockerEx mu_queue(VMOperationQueue_lock, | |
475 Mutex::_no_safepoint_check_flag); | |
476 safepoint_ops = _vm_queue->drain_at_safepoint_priority(); | |
477 } else { | |
478 safepoint_ops = NULL; | |
479 } | |
480 } while(safepoint_ops != NULL); | |
481 | |
482 _vm_queue->set_drain_list(NULL); | |
483 | |
484 // Complete safepoint synchronization | |
485 SafepointSynchronize::end(); | |
486 | |
487 } else { // not a safepoint operation | |
488 if (TraceLongCompiles) { | |
489 elapsedTimer t; | |
490 t.start(); | |
491 evaluate_operation(_cur_vm_operation); | |
492 t.stop(); | |
493 double secs = t.seconds(); | |
494 if (secs * 1e3 > LongCompileThreshold) { | |
495 // XXX - _cur_vm_operation should not be accessed after | |
496 // the completed count has been incremented; the waiting | |
497 // thread may have already freed this memory. | |
498 tty->print_cr("vm %s: %3.7f secs]", _cur_vm_operation->name(), secs); | |
499 } | |
500 } else { | |
501 evaluate_operation(_cur_vm_operation); | |
502 } | |
503 | |
504 _cur_vm_operation = NULL; | |
505 } | |
506 } | |
507 | |
508 // | |
509 // Notify (potential) waiting Java thread(s) - lock without safepoint | |
510 // check so that sneaking is not possible | |
511 { MutexLockerEx mu(VMOperationRequest_lock, | |
512 Mutex::_no_safepoint_check_flag); | |
513 VMOperationRequest_lock->notify_all(); | |
514 } | |
515 | |
516 // | |
517 // We want to make sure that we get to a safepoint regularly. | |
518 // | |
519 if (SafepointALot || SafepointSynchronize::is_cleanup_needed()) { | |
520 long interval = SafepointSynchronize::last_non_safepoint_interval(); | |
521 bool max_time_exceeded = GuaranteedSafepointInterval != 0 && (interval > GuaranteedSafepointInterval); | |
522 if (SafepointALot || max_time_exceeded) { | |
523 HandleMark hm(VMThread::vm_thread()); | |
524 SafepointSynchronize::begin(); | |
525 SafepointSynchronize::end(); | |
526 } | |
527 } | |
528 } | |
529 } | |
530 | |
531 void VMThread::execute(VM_Operation* op) { | |
532 Thread* t = Thread::current(); | |
533 | |
534 if (!t->is_VM_thread()) { | |
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535 SkipGCALot sgcalot(t); // avoid re-entrant attempts to gc-a-lot |
0 | 536 // JavaThread or WatcherThread |
537 t->check_for_valid_safepoint_state(true); | |
538 | |
539 // New request from Java thread, evaluate prologue | |
540 if (!op->doit_prologue()) { | |
541 return; // op was cancelled | |
542 } | |
543 | |
544 // Setup VM_operations for execution | |
545 op->set_calling_thread(t, Thread::get_priority(t)); | |
546 | |
547 // It does not make sense to execute the epilogue, if the VM operation object is getting | |
548 // deallocated by the VM thread. | |
549 bool concurrent = op->evaluate_concurrently(); | |
550 bool execute_epilog = !op->is_cheap_allocated(); | |
551 assert(!concurrent || op->is_cheap_allocated(), "concurrent => cheap_allocated"); | |
552 | |
553 // Get ticket number for non-concurrent VM operations | |
554 int ticket = 0; | |
555 if (!concurrent) { | |
556 ticket = t->vm_operation_ticket(); | |
557 } | |
558 | |
559 // Add VM operation to list of waiting threads. We are guaranteed not to block while holding the | |
560 // VMOperationQueue_lock, so we can block without a safepoint check. This allows vm operation requests | |
561 // to be queued up during a safepoint synchronization. | |
562 { | |
563 VMOperationQueue_lock->lock_without_safepoint_check(); | |
564 bool ok = _vm_queue->add(op); | |
565 op->set_timestamp(os::javaTimeMillis()); | |
566 VMOperationQueue_lock->notify(); | |
567 VMOperationQueue_lock->unlock(); | |
568 // VM_Operation got skipped | |
569 if (!ok) { | |
570 assert(concurrent, "can only skip concurrent tasks"); | |
571 if (op->is_cheap_allocated()) delete op; | |
572 return; | |
573 } | |
574 } | |
575 | |
576 if (!concurrent) { | |
577 // Wait for completion of request (non-concurrent) | |
578 // Note: only a JavaThread triggers the safepoint check when locking | |
579 MutexLocker mu(VMOperationRequest_lock); | |
580 while(t->vm_operation_completed_count() < ticket) { | |
581 VMOperationRequest_lock->wait(!t->is_Java_thread()); | |
582 } | |
583 } | |
584 | |
585 if (execute_epilog) { | |
586 op->doit_epilogue(); | |
587 } | |
588 } else { | |
589 // invoked by VM thread; usually nested VM operation | |
590 assert(t->is_VM_thread(), "must be a VM thread"); | |
591 VM_Operation* prev_vm_operation = vm_operation(); | |
592 if (prev_vm_operation != NULL) { | |
593 // Check the VM operation allows nested VM operation. This normally not the case, e.g., the compiler | |
594 // does not allow nested scavenges or compiles. | |
595 if (!prev_vm_operation->allow_nested_vm_operations()) { | |
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596 fatal(err_msg("Nested VM operation %s requested by operation %s", |
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597 op->name(), vm_operation()->name())); |
0 | 598 } |
599 op->set_calling_thread(prev_vm_operation->calling_thread(), prev_vm_operation->priority()); | |
600 } | |
601 | |
602 EventMark em("Executing %s VM operation: %s", prev_vm_operation ? "nested" : "", op->name()); | |
603 | |
604 // Release all internal handles after operation is evaluated | |
605 HandleMark hm(t); | |
606 _cur_vm_operation = op; | |
607 | |
608 if (op->evaluate_at_safepoint() && !SafepointSynchronize::is_at_safepoint()) { | |
609 SafepointSynchronize::begin(); | |
610 op->evaluate(); | |
611 SafepointSynchronize::end(); | |
612 } else { | |
613 op->evaluate(); | |
614 } | |
615 | |
616 // Free memory if needed | |
617 if (op->is_cheap_allocated()) delete op; | |
618 | |
619 _cur_vm_operation = prev_vm_operation; | |
620 } | |
621 } | |
622 | |
623 | |
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624 void VMThread::oops_do(OopClosure* f, CodeBlobClosure* cf) { |
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625 Thread::oops_do(f, cf); |
0 | 626 _vm_queue->oops_do(f); |
627 } | |
628 | |
629 //------------------------------------------------------------------------------------------------------------------ | |
630 #ifndef PRODUCT | |
631 | |
632 void VMOperationQueue::verify_queue(int prio) { | |
633 // Check that list is correctly linked | |
634 int length = _queue_length[prio]; | |
635 VM_Operation *cur = _queue[prio]; | |
636 int i; | |
637 | |
638 // Check forward links | |
639 for(i = 0; i < length; i++) { | |
640 cur = cur->next(); | |
641 assert(cur != _queue[prio], "list to short (forward)"); | |
642 } | |
643 assert(cur->next() == _queue[prio], "list to long (forward)"); | |
644 | |
645 // Check backwards links | |
646 cur = _queue[prio]; | |
647 for(i = 0; i < length; i++) { | |
648 cur = cur->prev(); | |
649 assert(cur != _queue[prio], "list to short (backwards)"); | |
650 } | |
651 assert(cur->prev() == _queue[prio], "list to long (backwards)"); | |
652 } | |
653 | |
654 #endif | |
655 | |
656 void VMThread::verify() { | |
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657 oops_do(&VerifyOopClosure::verify_oop, NULL); |
0 | 658 } |