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 }