1 /* 2 * Copyright (c) 2017, 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 "logging/log.hpp" 27 #include "logging/logStream.hpp" 28 #include "memory/resourceArea.hpp" 29 #include "runtime/handshake.hpp" 30 #include "runtime/interfaceSupport.hpp" 31 #include "runtime/osThread.hpp" 32 #include "runtime/semaphore.hpp" 33 #include "runtime/task.hpp" 34 #include "runtime/timerTrace.hpp" 35 #include "runtime/thread.hpp" 36 #include "runtime/vmThread.hpp" 37 #include "utilities/formatBuffer.hpp" 38 #include "utilities/preserveException.hpp" 39 40 #define ALL_JAVA_THREADS(X) for (JavaThread* X = Threads::first(); X; X = X->next()) 41 42 class HandshakeOperation: public StackObj { 43 public: 44 virtual void do_handshake(JavaThread* thread) = 0; 45 virtual void cancel_handshake(JavaThread* thread) = 0; 46 }; 47 48 class HandshakeThreadsOperation: public HandshakeOperation { 49 Semaphore _done; 50 ThreadClosure* _thread_cl; 51 52 public: 53 HandshakeThreadsOperation(ThreadClosure* cl) : _done(0), _thread_cl(cl) {} 54 void do_handshake(JavaThread* thread); 55 void cancel_handshake(JavaThread* thread) { _done.signal(); }; 56 57 bool thread_has_completed() { return _done.trywait(); } 58 }; 59 60 class VM_Handshake: public VM_Operation { 61 HandshakeThreadsOperation* const _op; 62 const jlong _handshake_timeout; 63 public: 64 bool evaluate_at_safepoint() const { return false; } 65 66 bool evaluate_concurrently() const { return false; } 67 68 protected: 69 70 VM_Handshake(HandshakeThreadsOperation* op) : 71 _op(op), 72 _handshake_timeout(TimeHelper::millis_to_counter(HandshakeTimeout)) {} 73 74 void set_handshake(JavaThread* target) { 75 target->set_handshake_operation(_op); 76 } 77 78 // This method returns true for threads completed their operation 79 // and true for threads canceled their operation. 80 // A cancellation can happen if the thread is exiting. 81 bool poll_for_completed_thread() { return _op->thread_has_completed(); } 82 83 bool handshake_has_timed_out(jlong start_time); 84 static void handle_timeout(); 85 }; 86 87 bool VM_Handshake::handshake_has_timed_out(jlong start_time) { 88 // Check if handshake operation has timed out 89 if (_handshake_timeout > 0) { 90 return os::elapsed_counter() >= (start_time + _handshake_timeout); 91 } 92 return false; 93 } 94 95 void VM_Handshake::handle_timeout() { 96 LogStreamHandle(Warning, handshake) log_stream; 97 MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag); 98 ALL_JAVA_THREADS(thr) { 99 if (thr->has_handshake()) { 100 log_stream.print("Thread " PTR_FORMAT " has not cleared its handshake op", p2i(thr)); 101 thr->print_thread_state_on(&log_stream); 102 } 103 } 104 log_stream.flush(); 105 fatal("Handshake operation timed out"); 106 } 107 108 109 class VM_HandshakeOneThread: public VM_Handshake { 110 JavaThread* _target; 111 bool _thread_alive; 112 public: 113 VM_HandshakeOneThread(HandshakeThreadsOperation* op, JavaThread* target) : 114 VM_Handshake(op), _target(target), _thread_alive(false) {} 115 116 void doit() { 117 TraceTime timer("Performing single-target operation (vmoperation doit)", TRACETIME_LOG(Info, handshake)); 118 119 { 120 MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag); 121 if (Threads::includes(_target)) { 122 set_handshake(_target); 123 _thread_alive = true; 124 } 125 } 126 127 if (!_thread_alive) { 128 return; 129 } 130 131 if (!UseMembar) { 132 os::serialize_thread_states(); 133 } 134 135 log_trace(handshake)("Thread signaled, begin processing by VMThtread"); 136 jlong start_time = os::elapsed_counter(); 137 do { 138 if (handshake_has_timed_out(start_time)) { 139 handle_timeout(); 140 } 141 142 MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag); 143 _target->handshake_process_by_vmthread(); 144 145 } while (!poll_for_completed_thread()); 146 } 147 148 VMOp_Type type() const { return VMOp_HandshakeOneThread; } 149 150 bool thread_alive() const { return _thread_alive; } 151 }; 152 153 class VM_HandshakeAllThreads: public VM_Handshake { 154 public: 155 VM_HandshakeAllThreads(HandshakeThreadsOperation* op) : VM_Handshake(op) {} 156 157 void doit() { 158 TraceTime timer("Performing operation (vmoperation doit)", TRACETIME_LOG(Info, handshake)); 159 160 int number_of_threads_issued = -1; 161 int number_of_threads_completed = 0; 162 { 163 MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag); 164 number_of_threads_issued = Threads::number_of_threads(); 165 166 ALL_JAVA_THREADS(thr) { 167 set_handshake(thr); 168 } 169 } 170 171 if (!UseMembar) { 172 os::serialize_thread_states(); 173 } 174 175 log_debug(handshake)("Threads signaled, begin processing blocked threads by VMThtread"); 176 const jlong start_time = os::elapsed_counter(); 177 do { 178 // Check if handshake operation has timed out 179 if (handshake_has_timed_out(start_time)) { 180 handle_timeout(); 181 } 182 183 // Have VM thread perform the handshake operation for blocked threads. 184 // Observing a blocked state may of course be transient but the processing is guarded 185 // by semaphores and we optimistically begin by working on the blocked threads 186 { 187 MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag); 188 ALL_JAVA_THREADS(thr) { 189 thr->handshake_process_by_vmthread(); 190 } 191 } 192 193 while (poll_for_completed_thread()) { 194 number_of_threads_completed++; 195 } 196 197 } while (number_of_threads_issued != number_of_threads_completed); 198 } 199 200 VMOp_Type type() const { return VMOp_HandshakeAllThreads; } 201 }; 202 203 class VM_HandshakeFallbackOperation : public VM_Operation { 204 ThreadClosure* _thread_cl; 205 Thread* _target_thread; 206 bool _all_threads; 207 bool _thread_alive; 208 public: 209 VM_HandshakeFallbackOperation(ThreadClosure* cl) : 210 _thread_cl(cl), _target_thread(NULL), _all_threads(true), _thread_alive(true) {} 211 VM_HandshakeFallbackOperation(ThreadClosure* cl, Thread* target) : 212 _thread_cl(cl), _target_thread(target), _all_threads(false), _thread_alive(false) {} 213 214 void doit() { 215 ALL_JAVA_THREADS(t) { 216 if (_all_threads || t == _target_thread) { 217 if (t == _target_thread) { 218 _thread_alive = true; 219 } 220 _thread_cl->do_thread(t); 221 } 222 } 223 } 224 225 VMOp_Type type() const { return VMOp_HandshakeFallback; } 226 bool thread_alive() const { return _thread_alive; } 227 }; 228 229 #undef ALL_JAVA_THREADS 230 231 void HandshakeThreadsOperation::do_handshake(JavaThread* thread) { 232 ResourceMark rm; 233 FormatBufferResource message("Operation for thread " PTR_FORMAT ", is_vm_thread: %s", 234 p2i(thread), BOOL_TO_STR(Thread::current()->is_VM_thread())); 235 TraceTime timer(message, TRACETIME_LOG(Debug, handshake, task)); 236 _thread_cl->do_thread(thread); 237 238 // Use the semaphore to inform the VM thread that we have completed the operation 239 _done.signal(); 240 } 241 242 void Handshake::execute(ThreadClosure* thread_cl) { 243 if (ThreadLocalHandshakes) { 244 HandshakeThreadsOperation cto(thread_cl); 245 VM_HandshakeAllThreads handshake(&cto); 246 VMThread::execute(&handshake); 247 } else { 248 VM_HandshakeFallbackOperation op(thread_cl); 249 VMThread::execute(&op); 250 } 251 } 252 253 bool Handshake::execute(ThreadClosure* thread_cl, JavaThread* target) { 254 if (ThreadLocalHandshakes) { 255 HandshakeThreadsOperation cto(thread_cl); 256 VM_HandshakeOneThread handshake(&cto, target); 257 VMThread::execute(&handshake); 258 return handshake.thread_alive(); 259 } else { 260 VM_HandshakeFallbackOperation op(thread_cl, target); 261 VMThread::execute(&op); 262 return op.thread_alive(); 263 } 264 } 265 266 HandshakeState::HandshakeState() : _operation(NULL), _semaphore(1), _vmthread_holds_semaphore(false), _thread_in_process_handshake(false) {} 267 268 void HandshakeState::set_operation(JavaThread* target, HandshakeOperation* op) { 269 _operation = op; 270 SafepointMechanism::arm_local_poll(target); 271 } 272 273 void HandshakeState::clear_handshake(JavaThread* target) { 274 _operation = NULL; 275 SafepointMechanism::disarm_local_poll(target); 276 } 277 278 void HandshakeState::process_self_inner(JavaThread* thread) { 279 assert(Thread::current() == thread, "should call from thread"); 280 CautiouslyPreserveExceptionMark pem(thread); 281 ThreadInVMForHandshake tivm(thread); 282 if (!_semaphore.trywait()) { 283 ThreadBlockInVM tbivm(thread); 284 _semaphore.wait(); 285 } 286 if (has_operation()) { 287 HandshakeOperation* op = _operation; 288 clear_handshake(thread); 289 if (op != NULL) { 290 op->do_handshake(thread); 291 } 292 } 293 _semaphore.signal(); 294 } 295 296 void HandshakeState::cancel_inner(JavaThread* thread) { 297 assert(Thread::current() == thread, "should call from thread"); 298 assert(thread->thread_state() == _thread_in_vm, "must be in vm state"); 299 #ifdef DEBUG 300 { 301 MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag); 302 assert(!Threads::includes(thread), "java thread must not be on threads list"); 303 } 304 #endif 305 HandshakeOperation* op = _operation; 306 clear_handshake(thread); 307 if (op != NULL) { 308 op->cancel_handshake(thread); 309 } 310 } 311 312 bool HandshakeState::vmthread_can_process_handshake(JavaThread* target) { 313 return SafepointSynchronize::safepoint_safe(target, target->thread_state()); 314 } 315 316 bool HandshakeState::claim_handshake_for_vmthread() { 317 if (_semaphore.trywait()) { 318 if (has_operation()) { 319 _vmthread_holds_semaphore = true; 320 } else { 321 _semaphore.signal(); 322 } 323 } 324 return _vmthread_holds_semaphore; 325 } 326 327 void HandshakeState::process_by_vmthread(JavaThread* target) { 328 assert(Thread::current()->is_VM_thread(), "should call from vm thread"); 329 330 if (!has_operation()) { 331 // JT has already cleared its handshake 332 return; 333 } 334 335 if (!vmthread_can_process_handshake(target)) { 336 // JT is observed in an unsafe state, it must notice the handshake itself 337 return; 338 } 339 340 // If we own the semaphore at this point and while owning the semaphore 341 // can observe a safe state the thread cannot possibly continue without 342 // getting caught by the semaphore. 343 if (claim_handshake_for_vmthread() && vmthread_can_process_handshake(target)) { 344 guarantee(!_semaphore.trywait(), "we should already own the semaphore"); 345 346 _operation->do_handshake(target); 347 clear_handshake(target); 348 _vmthread_holds_semaphore = false; 349 // Release the thread 350 _semaphore.signal(); 351 } 352 }