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annotate src/share/vm/runtime/vmThread.cpp @ 3806:1f4f4ae84625
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author | kvn |
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date | Wed, 13 Jul 2011 10:48:42 -0700 |
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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 | |
1972 | 25 #include "precompiled.hpp" |
26 #include "compiler/compileBroker.hpp" | |
27 #include "gc_interface/collectedHeap.hpp" | |
28 #include "memory/resourceArea.hpp" | |
29 #include "oops/methodOop.hpp" | |
30 #include "oops/oop.inline.hpp" | |
31 #include "runtime/interfaceSupport.hpp" | |
32 #include "runtime/mutexLocker.hpp" | |
33 #include "runtime/os.hpp" | |
34 #include "runtime/vmThread.hpp" | |
35 #include "runtime/vm_operations.hpp" | |
36 #include "services/runtimeService.hpp" | |
37 #include "utilities/dtrace.hpp" | |
38 #include "utilities/events.hpp" | |
39 #include "utilities/xmlstream.hpp" | |
40 #ifdef TARGET_OS_FAMILY_linux | |
41 # include "thread_linux.inline.hpp" | |
42 #endif | |
43 #ifdef TARGET_OS_FAMILY_solaris | |
44 # include "thread_solaris.inline.hpp" | |
45 #endif | |
46 #ifdef TARGET_OS_FAMILY_windows | |
47 # include "thread_windows.inline.hpp" | |
48 #endif | |
0 | 49 |
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50 HS_DTRACE_PROBE_DECL3(hotspot, vmops__request, char *, uintptr_t, int); |
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51 HS_DTRACE_PROBE_DECL3(hotspot, vmops__begin, char *, uintptr_t, int); |
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52 HS_DTRACE_PROBE_DECL3(hotspot, vmops__end, char *, uintptr_t, int); |
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53 |
0 | 54 // Dummy VM operation to act as first element in our circular double-linked list |
55 class VM_Dummy: public VM_Operation { | |
56 VMOp_Type type() const { return VMOp_Dummy; } | |
57 void doit() {}; | |
58 }; | |
59 | |
60 VMOperationQueue::VMOperationQueue() { | |
61 // The queue is a circular doubled-linked list, which always contains | |
62 // one element (i.e., one element means empty). | |
63 for(int i = 0; i < nof_priorities; i++) { | |
64 _queue_length[i] = 0; | |
65 _queue_counter = 0; | |
66 _queue[i] = new VM_Dummy(); | |
67 _queue[i]->set_next(_queue[i]); | |
68 _queue[i]->set_prev(_queue[i]); | |
69 } | |
70 _drain_list = NULL; | |
71 } | |
72 | |
73 | |
74 bool VMOperationQueue::queue_empty(int prio) { | |
75 // It is empty if there is exactly one element | |
76 bool empty = (_queue[prio] == _queue[prio]->next()); | |
77 assert( (_queue_length[prio] == 0 && empty) || | |
78 (_queue_length[prio] > 0 && !empty), "sanity check"); | |
79 return _queue_length[prio] == 0; | |
80 } | |
81 | |
82 // Inserts an element to the right of the q element | |
83 void VMOperationQueue::insert(VM_Operation* q, VM_Operation* n) { | |
84 assert(q->next()->prev() == q && q->prev()->next() == q, "sanity check"); | |
85 n->set_prev(q); | |
86 n->set_next(q->next()); | |
87 q->next()->set_prev(n); | |
88 q->set_next(n); | |
89 } | |
90 | |
91 void VMOperationQueue::queue_add_front(int prio, VM_Operation *op) { | |
92 _queue_length[prio]++; | |
93 insert(_queue[prio]->next(), op); | |
94 } | |
95 | |
96 void VMOperationQueue::queue_add_back(int prio, VM_Operation *op) { | |
97 _queue_length[prio]++; | |
98 insert(_queue[prio]->prev(), op); | |
99 } | |
100 | |
101 | |
102 void VMOperationQueue::unlink(VM_Operation* q) { | |
103 assert(q->next()->prev() == q && q->prev()->next() == q, "sanity check"); | |
104 q->prev()->set_next(q->next()); | |
105 q->next()->set_prev(q->prev()); | |
106 } | |
107 | |
108 VM_Operation* VMOperationQueue::queue_remove_front(int prio) { | |
109 if (queue_empty(prio)) return NULL; | |
110 assert(_queue_length[prio] >= 0, "sanity check"); | |
111 _queue_length[prio]--; | |
112 VM_Operation* r = _queue[prio]->next(); | |
113 assert(r != _queue[prio], "cannot remove base element"); | |
114 unlink(r); | |
115 return r; | |
116 } | |
117 | |
118 VM_Operation* VMOperationQueue::queue_drain(int prio) { | |
119 if (queue_empty(prio)) return NULL; | |
120 DEBUG_ONLY(int length = _queue_length[prio];); | |
121 assert(length >= 0, "sanity check"); | |
122 _queue_length[prio] = 0; | |
123 VM_Operation* r = _queue[prio]->next(); | |
124 assert(r != _queue[prio], "cannot remove base element"); | |
125 // remove links to base element from head and tail | |
126 r->set_prev(NULL); | |
127 _queue[prio]->prev()->set_next(NULL); | |
128 // restore queue to empty state | |
129 _queue[prio]->set_next(_queue[prio]); | |
130 _queue[prio]->set_prev(_queue[prio]); | |
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131 assert(queue_empty(prio), "drain corrupted queue"); |
0 | 132 #ifdef DEBUG |
133 int len = 0; | |
134 VM_Operation* cur; | |
135 for(cur = r; cur != NULL; cur=cur->next()) len++; | |
136 assert(len == length, "drain lost some ops"); | |
137 #endif | |
138 return r; | |
139 } | |
140 | |
141 void VMOperationQueue::queue_oops_do(int queue, OopClosure* f) { | |
142 VM_Operation* cur = _queue[queue]; | |
143 cur = cur->next(); | |
144 while (cur != _queue[queue]) { | |
145 cur->oops_do(f); | |
146 cur = cur->next(); | |
147 } | |
148 } | |
149 | |
150 void VMOperationQueue::drain_list_oops_do(OopClosure* f) { | |
151 VM_Operation* cur = _drain_list; | |
152 while (cur != NULL) { | |
153 cur->oops_do(f); | |
154 cur = cur->next(); | |
155 } | |
156 } | |
157 | |
158 //----------------------------------------------------------------- | |
159 // High-level interface | |
160 bool VMOperationQueue::add(VM_Operation *op) { | |
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161 |
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162 HS_DTRACE_PROBE3(hotspot, vmops__request, op->name(), strlen(op->name()), |
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163 op->evaluation_mode()); |
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164 |
0 | 165 // Encapsulates VM queue policy. Currently, that |
166 // only involves putting them on the right list | |
167 if (op->evaluate_at_safepoint()) { | |
168 queue_add_back(SafepointPriority, op); | |
169 return true; | |
170 } | |
171 | |
172 queue_add_back(MediumPriority, op); | |
173 return true; | |
174 } | |
175 | |
176 VM_Operation* VMOperationQueue::remove_next() { | |
177 // Assuming VMOperation queue is two-level priority queue. If there are | |
178 // more than two priorities, we need a different scheduling algorithm. | |
179 assert(SafepointPriority == 0 && MediumPriority == 1 && nof_priorities == 2, | |
180 "current algorithm does not work"); | |
181 | |
182 // simple counter based scheduling to prevent starvation of lower priority | |
183 // queue. -- see 4390175 | |
184 int high_prio, low_prio; | |
185 if (_queue_counter++ < 10) { | |
186 high_prio = SafepointPriority; | |
187 low_prio = MediumPriority; | |
188 } else { | |
189 _queue_counter = 0; | |
190 high_prio = MediumPriority; | |
191 low_prio = SafepointPriority; | |
192 } | |
193 | |
194 return queue_remove_front(queue_empty(high_prio) ? low_prio : high_prio); | |
195 } | |
196 | |
197 void VMOperationQueue::oops_do(OopClosure* f) { | |
198 for(int i = 0; i < nof_priorities; i++) { | |
199 queue_oops_do(i, f); | |
200 } | |
201 drain_list_oops_do(f); | |
202 } | |
203 | |
204 | |
205 //------------------------------------------------------------------------------------------------------------------ | |
206 // Implementation of VMThread stuff | |
207 | |
208 bool VMThread::_should_terminate = false; | |
209 bool VMThread::_terminated = false; | |
210 Monitor* VMThread::_terminate_lock = NULL; | |
211 VMThread* VMThread::_vm_thread = NULL; | |
212 VM_Operation* VMThread::_cur_vm_operation = NULL; | |
213 VMOperationQueue* VMThread::_vm_queue = NULL; | |
214 PerfCounter* VMThread::_perf_accumulated_vm_operation_time = NULL; | |
215 | |
216 | |
217 void VMThread::create() { | |
218 assert(vm_thread() == NULL, "we can only allocate one VMThread"); | |
219 _vm_thread = new VMThread(); | |
220 | |
221 // Create VM operation queue | |
222 _vm_queue = new VMOperationQueue(); | |
223 guarantee(_vm_queue != NULL, "just checking"); | |
224 | |
225 _terminate_lock = new Monitor(Mutex::safepoint, "VMThread::_terminate_lock", true); | |
226 | |
227 if (UsePerfData) { | |
228 // jvmstat performance counters | |
229 Thread* THREAD = Thread::current(); | |
230 _perf_accumulated_vm_operation_time = | |
231 PerfDataManager::create_counter(SUN_THREADS, "vmOperationTime", | |
232 PerfData::U_Ticks, CHECK); | |
233 } | |
234 } | |
235 | |
236 | |
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237 VMThread::VMThread() : NamedThread() { |
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238 set_name("VM Thread"); |
0 | 239 } |
240 | |
241 void VMThread::destroy() { | |
242 if (_vm_thread != NULL) { | |
243 delete _vm_thread; | |
244 _vm_thread = NULL; // VM thread is gone | |
245 } | |
246 } | |
247 | |
248 void VMThread::run() { | |
249 assert(this == vm_thread(), "check"); | |
250 | |
251 this->initialize_thread_local_storage(); | |
252 this->record_stack_base_and_size(); | |
253 // Notify_lock wait checks on active_handles() to rewait in | |
254 // case of spurious wakeup, it should wait on the last | |
255 // value set prior to the notify | |
256 this->set_active_handles(JNIHandleBlock::allocate_block()); | |
257 | |
258 { | |
259 MutexLocker ml(Notify_lock); | |
260 Notify_lock->notify(); | |
261 } | |
262 // Notify_lock is destroyed by Threads::create_vm() | |
263 | |
264 int prio = (VMThreadPriority == -1) | |
265 ? os::java_to_os_priority[NearMaxPriority] | |
266 : VMThreadPriority; | |
267 // Note that I cannot call os::set_priority because it expects Java | |
268 // priorities and I am *explicitly* using OS priorities so that it's | |
269 // possible to set the VM thread priority higher than any Java thread. | |
270 os::set_native_priority( this, prio ); | |
271 | |
272 // Wait for VM_Operations until termination | |
273 this->loop(); | |
274 | |
275 // Note the intention to exit before safepointing. | |
276 // 6295565 This has the effect of waiting for any large tty | |
277 // outputs to finish. | |
278 if (xtty != NULL) { | |
279 ttyLocker ttyl; | |
280 xtty->begin_elem("destroy_vm"); | |
281 xtty->stamp(); | |
282 xtty->end_elem(); | |
283 assert(should_terminate(), "termination flag must be set"); | |
284 } | |
285 | |
286 // 4526887 let VM thread exit at Safepoint | |
287 SafepointSynchronize::begin(); | |
288 | |
289 if (VerifyBeforeExit) { | |
290 HandleMark hm(VMThread::vm_thread()); | |
291 // Among other things, this ensures that Eden top is correct. | |
292 Universe::heap()->prepare_for_verify(); | |
293 os::check_heap(); | |
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294 // Silent verification so as not to pollute normal output, |
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295 // unless we really asked for it. |
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296 Universe::verify(true, !(PrintGCDetails || Verbose)); |
0 | 297 } |
298 | |
299 CompileBroker::set_should_block(); | |
300 | |
301 // wait for threads (compiler threads or daemon threads) in the | |
302 // _thread_in_native state to block. | |
303 VM_Exit::wait_for_threads_in_native_to_block(); | |
304 | |
305 // signal other threads that VM process is gone | |
306 { | |
307 // Note: we must have the _no_safepoint_check_flag. Mutex::lock() allows | |
308 // VM thread to enter any lock at Safepoint as long as its _owner is NULL. | |
309 // If that happens after _terminate_lock->wait() has unset _owner | |
310 // but before it actually drops the lock and waits, the notification below | |
311 // may get lost and we will have a hang. To avoid this, we need to use | |
312 // Mutex::lock_without_safepoint_check(). | |
313 MutexLockerEx ml(_terminate_lock, Mutex::_no_safepoint_check_flag); | |
314 _terminated = true; | |
315 _terminate_lock->notify(); | |
316 } | |
317 | |
318 // Deletion must be done synchronously by the JNI DestroyJavaVM thread | |
319 // so that the VMThread deletion completes before the main thread frees | |
320 // up the CodeHeap. | |
321 | |
322 } | |
323 | |
324 | |
325 // Notify the VMThread that the last non-daemon JavaThread has terminated, | |
326 // and wait until operation is performed. | |
327 void VMThread::wait_for_vm_thread_exit() { | |
328 { MutexLocker mu(VMOperationQueue_lock); | |
329 _should_terminate = true; | |
330 VMOperationQueue_lock->notify(); | |
331 } | |
332 | |
333 // Note: VM thread leaves at Safepoint. We are not stopped by Safepoint | |
334 // because this thread has been removed from the threads list. But anything | |
335 // that could get blocked by Safepoint should not be used after this point, | |
336 // otherwise we will hang, since there is no one can end the safepoint. | |
337 | |
338 // Wait until VM thread is terminated | |
339 // Note: it should be OK to use Terminator_lock here. But this is called | |
340 // at a very delicate time (VM shutdown) and we are operating in non- VM | |
341 // thread at Safepoint. It's safer to not share lock with other threads. | |
342 { MutexLockerEx ml(_terminate_lock, Mutex::_no_safepoint_check_flag); | |
343 while(!VMThread::is_terminated()) { | |
344 _terminate_lock->wait(Mutex::_no_safepoint_check_flag); | |
345 } | |
346 } | |
347 } | |
348 | |
349 void VMThread::print_on(outputStream* st) const { | |
350 st->print("\"%s\" ", name()); | |
351 Thread::print_on(st); | |
352 st->cr(); | |
353 } | |
354 | |
355 void VMThread::evaluate_operation(VM_Operation* op) { | |
356 ResourceMark rm; | |
357 | |
358 { | |
359 PerfTraceTime vm_op_timer(perf_accumulated_vm_operation_time()); | |
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360 HS_DTRACE_PROBE3(hotspot, vmops__begin, op->name(), strlen(op->name()), |
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361 op->evaluation_mode()); |
0 | 362 op->evaluate(); |
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363 HS_DTRACE_PROBE3(hotspot, vmops__end, op->name(), strlen(op->name()), |
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364 op->evaluation_mode()); |
0 | 365 } |
366 | |
367 // Last access of info in _cur_vm_operation! | |
368 bool c_heap_allocated = op->is_cheap_allocated(); | |
369 | |
370 // Mark as completed | |
371 if (!op->evaluate_concurrently()) { | |
372 op->calling_thread()->increment_vm_operation_completed_count(); | |
373 } | |
374 // It is unsafe to access the _cur_vm_operation after the 'increment_vm_operation_completed_count' call, | |
375 // since if it is stack allocated the calling thread might have deallocated | |
376 if (c_heap_allocated) { | |
377 delete _cur_vm_operation; | |
378 } | |
379 } | |
380 | |
381 | |
382 void VMThread::loop() { | |
383 assert(_cur_vm_operation == NULL, "no current one should be executing"); | |
384 | |
385 while(true) { | |
386 VM_Operation* safepoint_ops = NULL; | |
387 // | |
388 // Wait for VM operation | |
389 // | |
390 // use no_safepoint_check to get lock without attempting to "sneak" | |
391 { MutexLockerEx mu_queue(VMOperationQueue_lock, | |
392 Mutex::_no_safepoint_check_flag); | |
393 | |
394 // Look for new operation | |
395 assert(_cur_vm_operation == NULL, "no current one should be executing"); | |
396 _cur_vm_operation = _vm_queue->remove_next(); | |
397 | |
398 // Stall time tracking code | |
399 if (PrintVMQWaitTime && _cur_vm_operation != NULL && | |
400 !_cur_vm_operation->evaluate_concurrently()) { | |
401 long stall = os::javaTimeMillis() - _cur_vm_operation->timestamp(); | |
402 if (stall > 0) | |
403 tty->print_cr("%s stall: %Ld", _cur_vm_operation->name(), stall); | |
404 } | |
405 | |
406 while (!should_terminate() && _cur_vm_operation == NULL) { | |
407 // wait with a timeout to guarantee safepoints at regular intervals | |
408 bool timedout = | |
409 VMOperationQueue_lock->wait(Mutex::_no_safepoint_check_flag, | |
410 GuaranteedSafepointInterval); | |
411 | |
412 // Support for self destruction | |
413 if ((SelfDestructTimer != 0) && !is_error_reported() && | |
414 (os::elapsedTime() > SelfDestructTimer * 60)) { | |
415 tty->print_cr("VM self-destructed"); | |
416 exit(-1); | |
417 } | |
418 | |
419 if (timedout && (SafepointALot || | |
420 SafepointSynchronize::is_cleanup_needed())) { | |
421 MutexUnlockerEx mul(VMOperationQueue_lock, | |
422 Mutex::_no_safepoint_check_flag); | |
423 // Force a safepoint since we have not had one for at least | |
424 // 'GuaranteedSafepointInterval' milliseconds. This will run all | |
425 // the clean-up processing that needs to be done regularly at a | |
426 // safepoint | |
427 SafepointSynchronize::begin(); | |
428 #ifdef ASSERT | |
429 if (GCALotAtAllSafepoints) InterfaceSupport::check_gc_alot(); | |
430 #endif | |
431 SafepointSynchronize::end(); | |
432 } | |
433 _cur_vm_operation = _vm_queue->remove_next(); | |
434 | |
435 // If we are at a safepoint we will evaluate all the operations that | |
436 // follow that also require a safepoint | |
437 if (_cur_vm_operation != NULL && | |
438 _cur_vm_operation->evaluate_at_safepoint()) { | |
439 safepoint_ops = _vm_queue->drain_at_safepoint_priority(); | |
440 } | |
441 } | |
442 | |
443 if (should_terminate()) break; | |
444 } // Release mu_queue_lock | |
445 | |
446 // | |
447 // Execute VM operation | |
448 // | |
449 { HandleMark hm(VMThread::vm_thread()); | |
450 | |
451 EventMark em("Executing VM operation: %s", vm_operation()->name()); | |
452 assert(_cur_vm_operation != NULL, "we should have found an operation to execute"); | |
453 | |
454 // Give the VM thread an extra quantum. Jobs tend to be bursty and this | |
455 // helps the VM thread to finish up the job. | |
456 // FIXME: When this is enabled and there are many threads, this can degrade | |
457 // performance significantly. | |
458 if( VMThreadHintNoPreempt ) | |
459 os::hint_no_preempt(); | |
460 | |
461 // If we are at a safepoint we will evaluate all the operations that | |
462 // follow that also require a safepoint | |
463 if (_cur_vm_operation->evaluate_at_safepoint()) { | |
464 | |
465 _vm_queue->set_drain_list(safepoint_ops); // ensure ops can be scanned | |
466 | |
467 SafepointSynchronize::begin(); | |
468 evaluate_operation(_cur_vm_operation); | |
469 // now process all queued safepoint ops, iteratively draining | |
470 // the queue until there are none left | |
471 do { | |
472 _cur_vm_operation = safepoint_ops; | |
473 if (_cur_vm_operation != NULL) { | |
474 do { | |
475 // evaluate_operation deletes the op object so we have | |
476 // to grab the next op now | |
477 VM_Operation* next = _cur_vm_operation->next(); | |
478 _vm_queue->set_drain_list(next); | |
479 evaluate_operation(_cur_vm_operation); | |
480 _cur_vm_operation = next; | |
481 if (PrintSafepointStatistics) { | |
482 SafepointSynchronize::inc_vmop_coalesced_count(); | |
483 } | |
484 } while (_cur_vm_operation != NULL); | |
485 } | |
486 // There is a chance that a thread enqueued a safepoint op | |
487 // since we released the op-queue lock and initiated the safepoint. | |
488 // So we drain the queue again if there is anything there, as an | |
489 // optimization to try and reduce the number of safepoints. | |
490 // As the safepoint synchronizes us with JavaThreads we will see | |
491 // any enqueue made by a JavaThread, but the peek will not | |
492 // necessarily detect a concurrent enqueue by a GC thread, but | |
493 // that simply means the op will wait for the next major cycle of the | |
494 // VMThread - just as it would if the GC thread lost the race for | |
495 // the lock. | |
496 if (_vm_queue->peek_at_safepoint_priority()) { | |
497 // must hold lock while draining queue | |
498 MutexLockerEx mu_queue(VMOperationQueue_lock, | |
499 Mutex::_no_safepoint_check_flag); | |
500 safepoint_ops = _vm_queue->drain_at_safepoint_priority(); | |
501 } else { | |
502 safepoint_ops = NULL; | |
503 } | |
504 } while(safepoint_ops != NULL); | |
505 | |
506 _vm_queue->set_drain_list(NULL); | |
507 | |
508 // Complete safepoint synchronization | |
509 SafepointSynchronize::end(); | |
510 | |
511 } else { // not a safepoint operation | |
512 if (TraceLongCompiles) { | |
513 elapsedTimer t; | |
514 t.start(); | |
515 evaluate_operation(_cur_vm_operation); | |
516 t.stop(); | |
517 double secs = t.seconds(); | |
518 if (secs * 1e3 > LongCompileThreshold) { | |
519 // XXX - _cur_vm_operation should not be accessed after | |
520 // the completed count has been incremented; the waiting | |
521 // thread may have already freed this memory. | |
522 tty->print_cr("vm %s: %3.7f secs]", _cur_vm_operation->name(), secs); | |
523 } | |
524 } else { | |
525 evaluate_operation(_cur_vm_operation); | |
526 } | |
527 | |
528 _cur_vm_operation = NULL; | |
529 } | |
530 } | |
531 | |
532 // | |
533 // Notify (potential) waiting Java thread(s) - lock without safepoint | |
534 // check so that sneaking is not possible | |
535 { MutexLockerEx mu(VMOperationRequest_lock, | |
536 Mutex::_no_safepoint_check_flag); | |
537 VMOperationRequest_lock->notify_all(); | |
538 } | |
539 | |
540 // | |
541 // We want to make sure that we get to a safepoint regularly. | |
542 // | |
543 if (SafepointALot || SafepointSynchronize::is_cleanup_needed()) { | |
544 long interval = SafepointSynchronize::last_non_safepoint_interval(); | |
545 bool max_time_exceeded = GuaranteedSafepointInterval != 0 && (interval > GuaranteedSafepointInterval); | |
546 if (SafepointALot || max_time_exceeded) { | |
547 HandleMark hm(VMThread::vm_thread()); | |
548 SafepointSynchronize::begin(); | |
549 SafepointSynchronize::end(); | |
550 } | |
551 } | |
552 } | |
553 } | |
554 | |
555 void VMThread::execute(VM_Operation* op) { | |
556 Thread* t = Thread::current(); | |
557 | |
558 if (!t->is_VM_thread()) { | |
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559 SkipGCALot sgcalot(t); // avoid re-entrant attempts to gc-a-lot |
0 | 560 // JavaThread or WatcherThread |
561 t->check_for_valid_safepoint_state(true); | |
562 | |
563 // New request from Java thread, evaluate prologue | |
564 if (!op->doit_prologue()) { | |
565 return; // op was cancelled | |
566 } | |
567 | |
568 // Setup VM_operations for execution | |
569 op->set_calling_thread(t, Thread::get_priority(t)); | |
570 | |
571 // It does not make sense to execute the epilogue, if the VM operation object is getting | |
572 // deallocated by the VM thread. | |
573 bool concurrent = op->evaluate_concurrently(); | |
574 bool execute_epilog = !op->is_cheap_allocated(); | |
575 assert(!concurrent || op->is_cheap_allocated(), "concurrent => cheap_allocated"); | |
576 | |
577 // Get ticket number for non-concurrent VM operations | |
578 int ticket = 0; | |
579 if (!concurrent) { | |
580 ticket = t->vm_operation_ticket(); | |
581 } | |
582 | |
583 // Add VM operation to list of waiting threads. We are guaranteed not to block while holding the | |
584 // VMOperationQueue_lock, so we can block without a safepoint check. This allows vm operation requests | |
585 // to be queued up during a safepoint synchronization. | |
586 { | |
587 VMOperationQueue_lock->lock_without_safepoint_check(); | |
588 bool ok = _vm_queue->add(op); | |
589 op->set_timestamp(os::javaTimeMillis()); | |
590 VMOperationQueue_lock->notify(); | |
591 VMOperationQueue_lock->unlock(); | |
592 // VM_Operation got skipped | |
593 if (!ok) { | |
594 assert(concurrent, "can only skip concurrent tasks"); | |
595 if (op->is_cheap_allocated()) delete op; | |
596 return; | |
597 } | |
598 } | |
599 | |
600 if (!concurrent) { | |
601 // Wait for completion of request (non-concurrent) | |
602 // Note: only a JavaThread triggers the safepoint check when locking | |
603 MutexLocker mu(VMOperationRequest_lock); | |
604 while(t->vm_operation_completed_count() < ticket) { | |
605 VMOperationRequest_lock->wait(!t->is_Java_thread()); | |
606 } | |
607 } | |
608 | |
609 if (execute_epilog) { | |
610 op->doit_epilogue(); | |
611 } | |
612 } else { | |
613 // invoked by VM thread; usually nested VM operation | |
614 assert(t->is_VM_thread(), "must be a VM thread"); | |
615 VM_Operation* prev_vm_operation = vm_operation(); | |
616 if (prev_vm_operation != NULL) { | |
617 // Check the VM operation allows nested VM operation. This normally not the case, e.g., the compiler | |
618 // does not allow nested scavenges or compiles. | |
619 if (!prev_vm_operation->allow_nested_vm_operations()) { | |
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620 fatal(err_msg("Nested VM operation %s requested by operation %s", |
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621 op->name(), vm_operation()->name())); |
0 | 622 } |
623 op->set_calling_thread(prev_vm_operation->calling_thread(), prev_vm_operation->priority()); | |
624 } | |
625 | |
626 EventMark em("Executing %s VM operation: %s", prev_vm_operation ? "nested" : "", op->name()); | |
627 | |
628 // Release all internal handles after operation is evaluated | |
629 HandleMark hm(t); | |
630 _cur_vm_operation = op; | |
631 | |
632 if (op->evaluate_at_safepoint() && !SafepointSynchronize::is_at_safepoint()) { | |
633 SafepointSynchronize::begin(); | |
634 op->evaluate(); | |
635 SafepointSynchronize::end(); | |
636 } else { | |
637 op->evaluate(); | |
638 } | |
639 | |
640 // Free memory if needed | |
641 if (op->is_cheap_allocated()) delete op; | |
642 | |
643 _cur_vm_operation = prev_vm_operation; | |
644 } | |
645 } | |
646 | |
647 | |
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648 void VMThread::oops_do(OopClosure* f, CodeBlobClosure* cf) { |
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649 Thread::oops_do(f, cf); |
0 | 650 _vm_queue->oops_do(f); |
651 } | |
652 | |
653 //------------------------------------------------------------------------------------------------------------------ | |
654 #ifndef PRODUCT | |
655 | |
656 void VMOperationQueue::verify_queue(int prio) { | |
657 // Check that list is correctly linked | |
658 int length = _queue_length[prio]; | |
659 VM_Operation *cur = _queue[prio]; | |
660 int i; | |
661 | |
662 // Check forward links | |
663 for(i = 0; i < length; i++) { | |
664 cur = cur->next(); | |
665 assert(cur != _queue[prio], "list to short (forward)"); | |
666 } | |
667 assert(cur->next() == _queue[prio], "list to long (forward)"); | |
668 | |
669 // Check backwards links | |
670 cur = _queue[prio]; | |
671 for(i = 0; i < length; i++) { | |
672 cur = cur->prev(); | |
673 assert(cur != _queue[prio], "list to short (backwards)"); | |
674 } | |
675 assert(cur->prev() == _queue[prio], "list to long (backwards)"); | |
676 } | |
677 | |
678 #endif | |
679 | |
680 void VMThread::verify() { | |
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681 oops_do(&VerifyOopClosure::verify_oop, NULL); |
0 | 682 } |