Mercurial > hg > truffle
annotate src/share/vm/runtime/vmThread.cpp @ 17845:21dd1c827123
8033696: "assert(thread != NULL) failed: just checking" due to Thread::current() and JNI pthread interaction
Reviewed-by: dholmes, dsamersoff
Contributed-by: andreas.eriksson@oracle.com
| author | kevinw |
|---|---|
| date | Wed, 02 Apr 2014 18:40:52 +0200 |
| parents | f2110083203d |
| children | 78bbf4d43a14 |
| rev | line source |
|---|---|
| 0 | 1 /* |
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2 * Copyright (c) 1998, 2013, 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" | |
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29 #include "oops/method.hpp" |
| 1972 | 30 #include "oops/oop.inline.hpp" |
| 31 #include "runtime/interfaceSupport.hpp" | |
| 32 #include "runtime/mutexLocker.hpp" | |
| 33 #include "runtime/os.hpp" | |
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34 #include "runtime/thread.inline.hpp" |
| 1972 | 35 #include "runtime/vmThread.hpp" |
| 36 #include "runtime/vm_operations.hpp" | |
| 37 #include "services/runtimeService.hpp" | |
| 10405 | 38 #include "trace/tracing.hpp" |
| 1972 | 39 #include "utilities/dtrace.hpp" |
| 40 #include "utilities/events.hpp" | |
| 41 #include "utilities/xmlstream.hpp" | |
| 0 | 42 |
| 4006 | 43 #ifndef USDT2 |
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44 HS_DTRACE_PROBE_DECL3(hotspot, vmops__request, char *, uintptr_t, int); |
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45 HS_DTRACE_PROBE_DECL3(hotspot, vmops__begin, char *, uintptr_t, int); |
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46 HS_DTRACE_PROBE_DECL3(hotspot, vmops__end, char *, uintptr_t, int); |
| 4006 | 47 #endif /* !USDT2 */ |
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48 |
| 0 | 49 // Dummy VM operation to act as first element in our circular double-linked list |
| 50 class VM_Dummy: public VM_Operation { | |
| 51 VMOp_Type type() const { return VMOp_Dummy; } | |
| 52 void doit() {}; | |
| 53 }; | |
| 54 | |
| 55 VMOperationQueue::VMOperationQueue() { | |
| 56 // The queue is a circular doubled-linked list, which always contains | |
| 57 // one element (i.e., one element means empty). | |
| 58 for(int i = 0; i < nof_priorities; i++) { | |
| 59 _queue_length[i] = 0; | |
| 60 _queue_counter = 0; | |
| 61 _queue[i] = new VM_Dummy(); | |
| 62 _queue[i]->set_next(_queue[i]); | |
| 63 _queue[i]->set_prev(_queue[i]); | |
| 64 } | |
| 65 _drain_list = NULL; | |
| 66 } | |
| 67 | |
| 68 | |
| 69 bool VMOperationQueue::queue_empty(int prio) { | |
| 70 // It is empty if there is exactly one element | |
| 71 bool empty = (_queue[prio] == _queue[prio]->next()); | |
| 72 assert( (_queue_length[prio] == 0 && empty) || | |
| 73 (_queue_length[prio] > 0 && !empty), "sanity check"); | |
| 74 return _queue_length[prio] == 0; | |
| 75 } | |
| 76 | |
| 77 // Inserts an element to the right of the q element | |
| 78 void VMOperationQueue::insert(VM_Operation* q, VM_Operation* n) { | |
| 79 assert(q->next()->prev() == q && q->prev()->next() == q, "sanity check"); | |
| 80 n->set_prev(q); | |
| 81 n->set_next(q->next()); | |
| 82 q->next()->set_prev(n); | |
| 83 q->set_next(n); | |
| 84 } | |
| 85 | |
| 86 void VMOperationQueue::queue_add_front(int prio, VM_Operation *op) { | |
| 87 _queue_length[prio]++; | |
| 88 insert(_queue[prio]->next(), op); | |
| 89 } | |
| 90 | |
| 91 void VMOperationQueue::queue_add_back(int prio, VM_Operation *op) { | |
| 92 _queue_length[prio]++; | |
| 93 insert(_queue[prio]->prev(), op); | |
| 94 } | |
| 95 | |
| 96 | |
| 97 void VMOperationQueue::unlink(VM_Operation* q) { | |
| 98 assert(q->next()->prev() == q && q->prev()->next() == q, "sanity check"); | |
| 99 q->prev()->set_next(q->next()); | |
| 100 q->next()->set_prev(q->prev()); | |
| 101 } | |
| 102 | |
| 103 VM_Operation* VMOperationQueue::queue_remove_front(int prio) { | |
| 104 if (queue_empty(prio)) return NULL; | |
| 105 assert(_queue_length[prio] >= 0, "sanity check"); | |
| 106 _queue_length[prio]--; | |
| 107 VM_Operation* r = _queue[prio]->next(); | |
| 108 assert(r != _queue[prio], "cannot remove base element"); | |
| 109 unlink(r); | |
| 110 return r; | |
| 111 } | |
| 112 | |
| 113 VM_Operation* VMOperationQueue::queue_drain(int prio) { | |
| 114 if (queue_empty(prio)) return NULL; | |
| 115 DEBUG_ONLY(int length = _queue_length[prio];); | |
| 116 assert(length >= 0, "sanity check"); | |
| 117 _queue_length[prio] = 0; | |
| 118 VM_Operation* r = _queue[prio]->next(); | |
| 119 assert(r != _queue[prio], "cannot remove base element"); | |
| 120 // remove links to base element from head and tail | |
| 121 r->set_prev(NULL); | |
| 122 _queue[prio]->prev()->set_next(NULL); | |
| 123 // restore queue to empty state | |
| 124 _queue[prio]->set_next(_queue[prio]); | |
| 125 _queue[prio]->set_prev(_queue[prio]); | |
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126 assert(queue_empty(prio), "drain corrupted queue"); |
| 9152 | 127 #ifdef ASSERT |
| 0 | 128 int len = 0; |
| 129 VM_Operation* cur; | |
| 130 for(cur = r; cur != NULL; cur=cur->next()) len++; | |
| 131 assert(len == length, "drain lost some ops"); | |
| 132 #endif | |
| 133 return r; | |
| 134 } | |
| 135 | |
| 136 void VMOperationQueue::queue_oops_do(int queue, OopClosure* f) { | |
| 137 VM_Operation* cur = _queue[queue]; | |
| 138 cur = cur->next(); | |
| 139 while (cur != _queue[queue]) { | |
| 140 cur->oops_do(f); | |
| 141 cur = cur->next(); | |
| 142 } | |
| 143 } | |
| 144 | |
| 145 void VMOperationQueue::drain_list_oops_do(OopClosure* f) { | |
| 146 VM_Operation* cur = _drain_list; | |
| 147 while (cur != NULL) { | |
| 148 cur->oops_do(f); | |
| 149 cur = cur->next(); | |
| 150 } | |
| 151 } | |
| 152 | |
| 153 //----------------------------------------------------------------- | |
| 154 // High-level interface | |
| 155 bool VMOperationQueue::add(VM_Operation *op) { | |
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156 |
| 4006 | 157 #ifndef USDT2 |
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158 HS_DTRACE_PROBE3(hotspot, vmops__request, op->name(), strlen(op->name()), |
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159 op->evaluation_mode()); |
| 4006 | 160 #else /* USDT2 */ |
| 161 HOTSPOT_VMOPS_REQUEST( | |
| 162 (char *) op->name(), strlen(op->name()), | |
| 163 op->evaluation_mode()); | |
| 164 #endif /* USDT2 */ | |
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165 |
| 0 | 166 // Encapsulates VM queue policy. Currently, that |
| 167 // only involves putting them on the right list | |
| 168 if (op->evaluate_at_safepoint()) { | |
| 169 queue_add_back(SafepointPriority, op); | |
| 170 return true; | |
| 171 } | |
| 172 | |
| 173 queue_add_back(MediumPriority, op); | |
| 174 return true; | |
| 175 } | |
| 176 | |
| 177 VM_Operation* VMOperationQueue::remove_next() { | |
| 178 // Assuming VMOperation queue is two-level priority queue. If there are | |
| 179 // more than two priorities, we need a different scheduling algorithm. | |
| 180 assert(SafepointPriority == 0 && MediumPriority == 1 && nof_priorities == 2, | |
| 181 "current algorithm does not work"); | |
| 182 | |
| 183 // simple counter based scheduling to prevent starvation of lower priority | |
| 184 // queue. -- see 4390175 | |
| 185 int high_prio, low_prio; | |
| 186 if (_queue_counter++ < 10) { | |
| 187 high_prio = SafepointPriority; | |
| 188 low_prio = MediumPriority; | |
| 189 } else { | |
| 190 _queue_counter = 0; | |
| 191 high_prio = MediumPriority; | |
| 192 low_prio = SafepointPriority; | |
| 193 } | |
| 194 | |
| 195 return queue_remove_front(queue_empty(high_prio) ? low_prio : high_prio); | |
| 196 } | |
| 197 | |
| 198 void VMOperationQueue::oops_do(OopClosure* f) { | |
| 199 for(int i = 0; i < nof_priorities; i++) { | |
| 200 queue_oops_do(i, f); | |
| 201 } | |
| 202 drain_list_oops_do(f); | |
| 203 } | |
| 204 | |
| 205 | |
| 206 //------------------------------------------------------------------------------------------------------------------ | |
| 207 // Implementation of VMThread stuff | |
| 208 | |
| 209 bool VMThread::_should_terminate = false; | |
| 210 bool VMThread::_terminated = false; | |
| 211 Monitor* VMThread::_terminate_lock = NULL; | |
| 212 VMThread* VMThread::_vm_thread = NULL; | |
| 213 VM_Operation* VMThread::_cur_vm_operation = NULL; | |
| 214 VMOperationQueue* VMThread::_vm_queue = NULL; | |
| 215 PerfCounter* VMThread::_perf_accumulated_vm_operation_time = NULL; | |
| 216 | |
| 217 | |
| 218 void VMThread::create() { | |
| 219 assert(vm_thread() == NULL, "we can only allocate one VMThread"); | |
| 220 _vm_thread = new VMThread(); | |
| 221 | |
| 222 // Create VM operation queue | |
| 223 _vm_queue = new VMOperationQueue(); | |
| 224 guarantee(_vm_queue != NULL, "just checking"); | |
| 225 | |
| 226 _terminate_lock = new Monitor(Mutex::safepoint, "VMThread::_terminate_lock", true); | |
| 227 | |
| 228 if (UsePerfData) { | |
| 229 // jvmstat performance counters | |
| 230 Thread* THREAD = Thread::current(); | |
| 231 _perf_accumulated_vm_operation_time = | |
| 232 PerfDataManager::create_counter(SUN_THREADS, "vmOperationTime", | |
| 233 PerfData::U_Ticks, CHECK); | |
| 234 } | |
| 235 } | |
| 236 | |
| 237 | |
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238 VMThread::VMThread() : NamedThread() { |
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239 set_name("VM Thread"); |
| 0 | 240 } |
| 241 | |
| 242 void VMThread::destroy() { | |
| 243 if (_vm_thread != NULL) { | |
| 244 delete _vm_thread; | |
| 245 _vm_thread = NULL; // VM thread is gone | |
| 246 } | |
| 247 } | |
| 248 | |
| 249 void VMThread::run() { | |
| 250 assert(this == vm_thread(), "check"); | |
| 251 | |
| 252 this->initialize_thread_local_storage(); | |
| 253 this->record_stack_base_and_size(); | |
| 254 // Notify_lock wait checks on active_handles() to rewait in | |
| 255 // case of spurious wakeup, it should wait on the last | |
| 256 // value set prior to the notify | |
| 257 this->set_active_handles(JNIHandleBlock::allocate_block()); | |
| 258 | |
| 259 { | |
| 260 MutexLocker ml(Notify_lock); | |
| 261 Notify_lock->notify(); | |
| 262 } | |
| 263 // Notify_lock is destroyed by Threads::create_vm() | |
| 264 | |
| 265 int prio = (VMThreadPriority == -1) | |
| 266 ? os::java_to_os_priority[NearMaxPriority] | |
| 267 : VMThreadPriority; | |
| 268 // Note that I cannot call os::set_priority because it expects Java | |
| 269 // priorities and I am *explicitly* using OS priorities so that it's | |
| 270 // possible to set the VM thread priority higher than any Java thread. | |
| 271 os::set_native_priority( this, prio ); | |
| 272 | |
| 273 // Wait for VM_Operations until termination | |
| 274 this->loop(); | |
| 275 | |
| 276 // Note the intention to exit before safepointing. | |
| 277 // 6295565 This has the effect of waiting for any large tty | |
| 278 // outputs to finish. | |
| 279 if (xtty != NULL) { | |
| 280 ttyLocker ttyl; | |
| 281 xtty->begin_elem("destroy_vm"); | |
| 282 xtty->stamp(); | |
| 283 xtty->end_elem(); | |
| 284 assert(should_terminate(), "termination flag must be set"); | |
| 285 } | |
| 286 | |
| 287 // 4526887 let VM thread exit at Safepoint | |
| 288 SafepointSynchronize::begin(); | |
| 289 | |
| 290 if (VerifyBeforeExit) { | |
| 291 HandleMark hm(VMThread::vm_thread()); | |
| 292 // Among other things, this ensures that Eden top is correct. | |
| 293 Universe::heap()->prepare_for_verify(); | |
| 294 os::check_heap(); | |
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295 // Silent verification so as not to pollute normal output, |
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296 // unless we really asked for it. |
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297 Universe::verify(!(PrintGCDetails || Verbose) || VerifySilently); |
| 0 | 298 } |
| 299 | |
| 300 CompileBroker::set_should_block(); | |
| 301 | |
| 302 // wait for threads (compiler threads or daemon threads) in the | |
| 303 // _thread_in_native state to block. | |
| 304 VM_Exit::wait_for_threads_in_native_to_block(); | |
| 305 | |
| 306 // signal other threads that VM process is gone | |
| 307 { | |
| 308 // Note: we must have the _no_safepoint_check_flag. Mutex::lock() allows | |
| 309 // VM thread to enter any lock at Safepoint as long as its _owner is NULL. | |
| 310 // If that happens after _terminate_lock->wait() has unset _owner | |
| 311 // but before it actually drops the lock and waits, the notification below | |
| 312 // may get lost and we will have a hang. To avoid this, we need to use | |
| 313 // Mutex::lock_without_safepoint_check(). | |
| 314 MutexLockerEx ml(_terminate_lock, Mutex::_no_safepoint_check_flag); | |
| 315 _terminated = true; | |
| 316 _terminate_lock->notify(); | |
| 317 } | |
| 318 | |
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319 // Thread destructor usually does this. |
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320 ThreadLocalStorage::set_thread(NULL); |
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321 |
| 0 | 322 // Deletion must be done synchronously by the JNI DestroyJavaVM thread |
| 323 // so that the VMThread deletion completes before the main thread frees | |
| 324 // up the CodeHeap. | |
| 325 | |
| 326 } | |
| 327 | |
| 328 | |
| 329 // Notify the VMThread that the last non-daemon JavaThread has terminated, | |
| 330 // and wait until operation is performed. | |
| 331 void VMThread::wait_for_vm_thread_exit() { | |
| 332 { MutexLocker mu(VMOperationQueue_lock); | |
| 333 _should_terminate = true; | |
| 334 VMOperationQueue_lock->notify(); | |
| 335 } | |
| 336 | |
| 337 // Note: VM thread leaves at Safepoint. We are not stopped by Safepoint | |
| 338 // because this thread has been removed from the threads list. But anything | |
| 339 // that could get blocked by Safepoint should not be used after this point, | |
| 340 // otherwise we will hang, since there is no one can end the safepoint. | |
| 341 | |
| 342 // Wait until VM thread is terminated | |
| 343 // Note: it should be OK to use Terminator_lock here. But this is called | |
| 344 // at a very delicate time (VM shutdown) and we are operating in non- VM | |
| 345 // thread at Safepoint. It's safer to not share lock with other threads. | |
| 346 { MutexLockerEx ml(_terminate_lock, Mutex::_no_safepoint_check_flag); | |
| 347 while(!VMThread::is_terminated()) { | |
| 348 _terminate_lock->wait(Mutex::_no_safepoint_check_flag); | |
| 349 } | |
| 350 } | |
| 351 } | |
| 352 | |
| 353 void VMThread::print_on(outputStream* st) const { | |
| 354 st->print("\"%s\" ", name()); | |
| 355 Thread::print_on(st); | |
| 356 st->cr(); | |
| 357 } | |
| 358 | |
| 359 void VMThread::evaluate_operation(VM_Operation* op) { | |
| 360 ResourceMark rm; | |
| 361 | |
| 362 { | |
| 363 PerfTraceTime vm_op_timer(perf_accumulated_vm_operation_time()); | |
| 4006 | 364 #ifndef USDT2 |
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365 HS_DTRACE_PROBE3(hotspot, vmops__begin, op->name(), strlen(op->name()), |
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366 op->evaluation_mode()); |
| 4006 | 367 #else /* USDT2 */ |
| 368 HOTSPOT_VMOPS_BEGIN( | |
| 369 (char *) op->name(), strlen(op->name()), | |
| 370 op->evaluation_mode()); | |
| 371 #endif /* USDT2 */ | |
| 10405 | 372 |
| 373 EventExecuteVMOperation event; | |
| 374 | |
| 0 | 375 op->evaluate(); |
| 10405 | 376 |
| 377 if (event.should_commit()) { | |
| 378 bool is_concurrent = op->evaluate_concurrently(); | |
| 379 event.set_operation(op->type()); | |
| 380 event.set_safepoint(op->evaluate_at_safepoint()); | |
| 381 event.set_blocking(!is_concurrent); | |
| 382 // Only write caller thread information for non-concurrent vm operations. | |
| 383 // For concurrent vm operations, the thread id is set to 0 indicating thread is unknown. | |
| 384 // This is because the caller thread could have exited already. | |
| 385 event.set_caller(is_concurrent ? 0 : op->calling_thread()->osthread()->thread_id()); | |
| 386 event.commit(); | |
| 387 } | |
| 388 | |
| 4006 | 389 #ifndef USDT2 |
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390 HS_DTRACE_PROBE3(hotspot, vmops__end, op->name(), strlen(op->name()), |
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391 op->evaluation_mode()); |
| 4006 | 392 #else /* USDT2 */ |
| 393 HOTSPOT_VMOPS_END( | |
| 394 (char *) op->name(), strlen(op->name()), | |
| 395 op->evaluation_mode()); | |
| 396 #endif /* USDT2 */ | |
| 0 | 397 } |
| 398 | |
| 399 // Last access of info in _cur_vm_operation! | |
| 400 bool c_heap_allocated = op->is_cheap_allocated(); | |
| 401 | |
| 402 // Mark as completed | |
| 403 if (!op->evaluate_concurrently()) { | |
| 404 op->calling_thread()->increment_vm_operation_completed_count(); | |
| 405 } | |
| 406 // It is unsafe to access the _cur_vm_operation after the 'increment_vm_operation_completed_count' call, | |
| 407 // since if it is stack allocated the calling thread might have deallocated | |
| 408 if (c_heap_allocated) { | |
| 409 delete _cur_vm_operation; | |
| 410 } | |
| 411 } | |
| 412 | |
| 413 | |
| 414 void VMThread::loop() { | |
| 415 assert(_cur_vm_operation == NULL, "no current one should be executing"); | |
| 416 | |
| 417 while(true) { | |
| 418 VM_Operation* safepoint_ops = NULL; | |
| 419 // | |
| 420 // Wait for VM operation | |
| 421 // | |
| 422 // use no_safepoint_check to get lock without attempting to "sneak" | |
| 423 { MutexLockerEx mu_queue(VMOperationQueue_lock, | |
| 424 Mutex::_no_safepoint_check_flag); | |
| 425 | |
| 426 // Look for new operation | |
| 427 assert(_cur_vm_operation == NULL, "no current one should be executing"); | |
| 428 _cur_vm_operation = _vm_queue->remove_next(); | |
| 429 | |
| 430 // Stall time tracking code | |
| 431 if (PrintVMQWaitTime && _cur_vm_operation != NULL && | |
| 432 !_cur_vm_operation->evaluate_concurrently()) { | |
| 433 long stall = os::javaTimeMillis() - _cur_vm_operation->timestamp(); | |
| 434 if (stall > 0) | |
| 435 tty->print_cr("%s stall: %Ld", _cur_vm_operation->name(), stall); | |
| 436 } | |
| 437 | |
| 438 while (!should_terminate() && _cur_vm_operation == NULL) { | |
| 439 // wait with a timeout to guarantee safepoints at regular intervals | |
| 440 bool timedout = | |
| 441 VMOperationQueue_lock->wait(Mutex::_no_safepoint_check_flag, | |
| 442 GuaranteedSafepointInterval); | |
| 443 | |
| 444 // Support for self destruction | |
| 445 if ((SelfDestructTimer != 0) && !is_error_reported() && | |
| 446 (os::elapsedTime() > SelfDestructTimer * 60)) { | |
| 447 tty->print_cr("VM self-destructed"); | |
| 448 exit(-1); | |
| 449 } | |
| 450 | |
| 451 if (timedout && (SafepointALot || | |
| 452 SafepointSynchronize::is_cleanup_needed())) { | |
| 453 MutexUnlockerEx mul(VMOperationQueue_lock, | |
| 454 Mutex::_no_safepoint_check_flag); | |
| 455 // Force a safepoint since we have not had one for at least | |
| 456 // 'GuaranteedSafepointInterval' milliseconds. This will run all | |
| 457 // the clean-up processing that needs to be done regularly at a | |
| 458 // safepoint | |
| 459 SafepointSynchronize::begin(); | |
| 460 #ifdef ASSERT | |
| 461 if (GCALotAtAllSafepoints) InterfaceSupport::check_gc_alot(); | |
| 462 #endif | |
| 463 SafepointSynchronize::end(); | |
| 464 } | |
| 465 _cur_vm_operation = _vm_queue->remove_next(); | |
| 466 | |
| 467 // If we are at a safepoint we will evaluate all the operations that | |
| 468 // follow that also require a safepoint | |
| 469 if (_cur_vm_operation != NULL && | |
| 470 _cur_vm_operation->evaluate_at_safepoint()) { | |
| 471 safepoint_ops = _vm_queue->drain_at_safepoint_priority(); | |
| 472 } | |
| 473 } | |
| 474 | |
| 475 if (should_terminate()) break; | |
| 476 } // Release mu_queue_lock | |
| 477 | |
| 478 // | |
| 479 // Execute VM operation | |
| 480 // | |
| 481 { HandleMark hm(VMThread::vm_thread()); | |
| 482 | |
| 483 EventMark em("Executing VM operation: %s", vm_operation()->name()); | |
| 484 assert(_cur_vm_operation != NULL, "we should have found an operation to execute"); | |
| 485 | |
| 486 // Give the VM thread an extra quantum. Jobs tend to be bursty and this | |
| 487 // helps the VM thread to finish up the job. | |
| 488 // FIXME: When this is enabled and there are many threads, this can degrade | |
| 489 // performance significantly. | |
| 490 if( VMThreadHintNoPreempt ) | |
| 491 os::hint_no_preempt(); | |
| 492 | |
| 493 // If we are at a safepoint we will evaluate all the operations that | |
| 494 // follow that also require a safepoint | |
| 495 if (_cur_vm_operation->evaluate_at_safepoint()) { | |
| 496 | |
| 497 _vm_queue->set_drain_list(safepoint_ops); // ensure ops can be scanned | |
| 498 | |
| 499 SafepointSynchronize::begin(); | |
| 500 evaluate_operation(_cur_vm_operation); | |
| 501 // now process all queued safepoint ops, iteratively draining | |
| 502 // the queue until there are none left | |
| 503 do { | |
| 504 _cur_vm_operation = safepoint_ops; | |
| 505 if (_cur_vm_operation != NULL) { | |
| 506 do { | |
| 507 // evaluate_operation deletes the op object so we have | |
| 508 // to grab the next op now | |
| 509 VM_Operation* next = _cur_vm_operation->next(); | |
| 510 _vm_queue->set_drain_list(next); | |
| 511 evaluate_operation(_cur_vm_operation); | |
| 512 _cur_vm_operation = next; | |
| 513 if (PrintSafepointStatistics) { | |
| 514 SafepointSynchronize::inc_vmop_coalesced_count(); | |
| 515 } | |
| 516 } while (_cur_vm_operation != NULL); | |
| 517 } | |
| 518 // There is a chance that a thread enqueued a safepoint op | |
| 519 // since we released the op-queue lock and initiated the safepoint. | |
| 520 // So we drain the queue again if there is anything there, as an | |
| 521 // optimization to try and reduce the number of safepoints. | |
| 522 // As the safepoint synchronizes us with JavaThreads we will see | |
| 523 // any enqueue made by a JavaThread, but the peek will not | |
| 524 // necessarily detect a concurrent enqueue by a GC thread, but | |
| 525 // that simply means the op will wait for the next major cycle of the | |
| 526 // VMThread - just as it would if the GC thread lost the race for | |
| 527 // the lock. | |
| 528 if (_vm_queue->peek_at_safepoint_priority()) { | |
| 529 // must hold lock while draining queue | |
| 530 MutexLockerEx mu_queue(VMOperationQueue_lock, | |
| 531 Mutex::_no_safepoint_check_flag); | |
| 532 safepoint_ops = _vm_queue->drain_at_safepoint_priority(); | |
| 533 } else { | |
| 534 safepoint_ops = NULL; | |
| 535 } | |
| 536 } while(safepoint_ops != NULL); | |
| 537 | |
| 538 _vm_queue->set_drain_list(NULL); | |
| 539 | |
| 540 // Complete safepoint synchronization | |
| 541 SafepointSynchronize::end(); | |
| 542 | |
| 543 } else { // not a safepoint operation | |
| 544 if (TraceLongCompiles) { | |
| 545 elapsedTimer t; | |
| 546 t.start(); | |
| 547 evaluate_operation(_cur_vm_operation); | |
| 548 t.stop(); | |
| 549 double secs = t.seconds(); | |
| 550 if (secs * 1e3 > LongCompileThreshold) { | |
| 551 // XXX - _cur_vm_operation should not be accessed after | |
| 552 // the completed count has been incremented; the waiting | |
| 553 // thread may have already freed this memory. | |
| 554 tty->print_cr("vm %s: %3.7f secs]", _cur_vm_operation->name(), secs); | |
| 555 } | |
| 556 } else { | |
| 557 evaluate_operation(_cur_vm_operation); | |
| 558 } | |
| 559 | |
| 560 _cur_vm_operation = NULL; | |
| 561 } | |
| 562 } | |
| 563 | |
| 564 // | |
| 565 // Notify (potential) waiting Java thread(s) - lock without safepoint | |
| 566 // check so that sneaking is not possible | |
| 567 { MutexLockerEx mu(VMOperationRequest_lock, | |
| 568 Mutex::_no_safepoint_check_flag); | |
| 569 VMOperationRequest_lock->notify_all(); | |
| 570 } | |
| 571 | |
| 572 // | |
| 573 // We want to make sure that we get to a safepoint regularly. | |
| 574 // | |
| 575 if (SafepointALot || SafepointSynchronize::is_cleanup_needed()) { | |
| 576 long interval = SafepointSynchronize::last_non_safepoint_interval(); | |
| 577 bool max_time_exceeded = GuaranteedSafepointInterval != 0 && (interval > GuaranteedSafepointInterval); | |
| 578 if (SafepointALot || max_time_exceeded) { | |
| 579 HandleMark hm(VMThread::vm_thread()); | |
| 580 SafepointSynchronize::begin(); | |
| 581 SafepointSynchronize::end(); | |
| 582 } | |
| 583 } | |
| 584 } | |
| 585 } | |
| 586 | |
| 587 void VMThread::execute(VM_Operation* op) { | |
| 588 Thread* t = Thread::current(); | |
| 589 | |
| 590 if (!t->is_VM_thread()) { | |
|
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591 SkipGCALot sgcalot(t); // avoid re-entrant attempts to gc-a-lot |
| 0 | 592 // JavaThread or WatcherThread |
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593 bool concurrent = op->evaluate_concurrently(); |
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594 // only blocking VM operations need to verify the caller's safepoint state: |
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595 if (!concurrent) { |
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596 t->check_for_valid_safepoint_state(true); |
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597 } |
| 0 | 598 |
| 599 // New request from Java thread, evaluate prologue | |
| 600 if (!op->doit_prologue()) { | |
| 601 return; // op was cancelled | |
| 602 } | |
| 603 | |
| 604 // Setup VM_operations for execution | |
| 605 op->set_calling_thread(t, Thread::get_priority(t)); | |
| 606 | |
| 607 // It does not make sense to execute the epilogue, if the VM operation object is getting | |
| 608 // deallocated by the VM thread. | |
| 609 bool execute_epilog = !op->is_cheap_allocated(); | |
| 610 assert(!concurrent || op->is_cheap_allocated(), "concurrent => cheap_allocated"); | |
| 611 | |
| 612 // Get ticket number for non-concurrent VM operations | |
| 613 int ticket = 0; | |
| 614 if (!concurrent) { | |
| 615 ticket = t->vm_operation_ticket(); | |
| 616 } | |
| 617 | |
| 618 // Add VM operation to list of waiting threads. We are guaranteed not to block while holding the | |
| 619 // VMOperationQueue_lock, so we can block without a safepoint check. This allows vm operation requests | |
| 620 // to be queued up during a safepoint synchronization. | |
| 621 { | |
| 622 VMOperationQueue_lock->lock_without_safepoint_check(); | |
| 623 bool ok = _vm_queue->add(op); | |
| 10405 | 624 op->set_timestamp(os::javaTimeMillis()); |
| 0 | 625 VMOperationQueue_lock->notify(); |
| 626 VMOperationQueue_lock->unlock(); | |
| 627 // VM_Operation got skipped | |
| 628 if (!ok) { | |
| 629 assert(concurrent, "can only skip concurrent tasks"); | |
| 630 if (op->is_cheap_allocated()) delete op; | |
| 631 return; | |
| 632 } | |
| 633 } | |
| 634 | |
| 635 if (!concurrent) { | |
| 636 // Wait for completion of request (non-concurrent) | |
| 637 // Note: only a JavaThread triggers the safepoint check when locking | |
| 638 MutexLocker mu(VMOperationRequest_lock); | |
| 639 while(t->vm_operation_completed_count() < ticket) { | |
| 640 VMOperationRequest_lock->wait(!t->is_Java_thread()); | |
| 641 } | |
| 642 } | |
| 643 | |
| 644 if (execute_epilog) { | |
| 645 op->doit_epilogue(); | |
| 646 } | |
| 647 } else { | |
| 648 // invoked by VM thread; usually nested VM operation | |
| 649 assert(t->is_VM_thread(), "must be a VM thread"); | |
| 650 VM_Operation* prev_vm_operation = vm_operation(); | |
| 651 if (prev_vm_operation != NULL) { | |
| 652 // Check the VM operation allows nested VM operation. This normally not the case, e.g., the compiler | |
| 653 // does not allow nested scavenges or compiles. | |
| 654 if (!prev_vm_operation->allow_nested_vm_operations()) { | |
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655 fatal(err_msg("Nested VM operation %s requested by operation %s", |
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656 op->name(), vm_operation()->name())); |
| 0 | 657 } |
| 658 op->set_calling_thread(prev_vm_operation->calling_thread(), prev_vm_operation->priority()); | |
| 659 } | |
| 660 | |
| 661 EventMark em("Executing %s VM operation: %s", prev_vm_operation ? "nested" : "", op->name()); | |
| 662 | |
| 663 // Release all internal handles after operation is evaluated | |
| 664 HandleMark hm(t); | |
| 665 _cur_vm_operation = op; | |
| 666 | |
| 667 if (op->evaluate_at_safepoint() && !SafepointSynchronize::is_at_safepoint()) { | |
| 668 SafepointSynchronize::begin(); | |
| 669 op->evaluate(); | |
| 670 SafepointSynchronize::end(); | |
| 671 } else { | |
| 672 op->evaluate(); | |
| 673 } | |
| 674 | |
| 675 // Free memory if needed | |
| 676 if (op->is_cheap_allocated()) delete op; | |
| 677 | |
| 678 _cur_vm_operation = prev_vm_operation; | |
| 679 } | |
| 680 } | |
| 681 | |
| 682 | |
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683 void VMThread::oops_do(OopClosure* f, CLDToOopClosure* cld_f, CodeBlobClosure* cf) { |
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684 Thread::oops_do(f, cld_f, cf); |
| 0 | 685 _vm_queue->oops_do(f); |
| 686 } | |
| 687 | |
| 688 //------------------------------------------------------------------------------------------------------------------ | |
| 689 #ifndef PRODUCT | |
| 690 | |
| 691 void VMOperationQueue::verify_queue(int prio) { | |
| 692 // Check that list is correctly linked | |
| 693 int length = _queue_length[prio]; | |
| 694 VM_Operation *cur = _queue[prio]; | |
| 695 int i; | |
| 696 | |
| 697 // Check forward links | |
| 698 for(i = 0; i < length; i++) { | |
| 699 cur = cur->next(); | |
| 700 assert(cur != _queue[prio], "list to short (forward)"); | |
| 701 } | |
| 702 assert(cur->next() == _queue[prio], "list to long (forward)"); | |
| 703 | |
| 704 // Check backwards links | |
| 705 cur = _queue[prio]; | |
| 706 for(i = 0; i < length; i++) { | |
| 707 cur = cur->prev(); | |
| 708 assert(cur != _queue[prio], "list to short (backwards)"); | |
| 709 } | |
| 710 assert(cur->prev() == _queue[prio], "list to long (backwards)"); | |
| 711 } | |
| 712 | |
| 713 #endif | |
| 714 | |
| 715 void VMThread::verify() { | |
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716 oops_do(&VerifyOopClosure::verify_oop, NULL, NULL); |
| 0 | 717 } |