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src/hotspot/share/runtime/handshake.cpp

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rev 47863 : imported patch 10.08.open.rebase_20171114.rehn
rev 47865 : dholmes CR: Fix indents, trailing spaces and various typos. Add descriptions for the '_cnt', '_max' and '_times" fields, add impl notes to document the type choices.


 120         _thread_alive = true;
 121       }
 122     }
 123 
 124     if (!_thread_alive) {
 125       return;
 126     }
 127 
 128     if (!UseMembar) {
 129       os::serialize_thread_states();
 130     }
 131 
 132     log_trace(handshake)("Thread signaled, begin processing by VMThtread");
 133     jlong start_time = os::elapsed_counter();
 134     do {
 135       if (handshake_has_timed_out(start_time)) {
 136         handle_timeout();
 137       }
 138 
 139       // We need to re-think this with SMR ThreadsList.
 140       // There is assumption in code that Threads_lock should be lock
 141       // during certain phases.
 142       MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
 143       ThreadsListHandle tlh;
 144       if (tlh.includes(_target)) { 
 145         // Warning threads address might be re-used.
 146         // handshake_process_by_vmthread will check the semaphore for us again
 147         // Since we can't have more then one handshake in flight a reuse of thread address
 148         // should be okey since the new thread will not have an operation.

 149         _target->handshake_process_by_vmthread();
 150       } else {
 151         // We can't warn here is since the thread do cancel_handshake after it have been removed
 152         // from ThreadsList. So we should just keep looping here until while below return negative
 153         // If we have a bug, then we deadlock here, which is good for debugging.

 154       }
 155 
 156     } while (!poll_for_completed_thread());
 157   }
 158 
 159   VMOp_Type type() const { return VMOp_HandshakeOneThread; }
 160 
 161   bool thread_alive() const { return _thread_alive; }
 162 };
 163 
 164 class VM_HandshakeAllThreads: public VM_Handshake {
 165  public:
 166   VM_HandshakeAllThreads(HandshakeThreadsOperation* op) : VM_Handshake(op) {}
 167 
 168   void doit() {
 169     TraceTime timer("Performing operation (vmoperation doit)", TRACETIME_LOG(Info, handshake));
 170 
 171     int number_of_threads_issued = 0;
 172     for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thr = jtiwh.next(); ) {
 173       set_handshake(thr);
 174       number_of_threads_issued++;
 175     }


 180     }
 181 
 182     if (!UseMembar) {
 183       os::serialize_thread_states();
 184     }
 185 
 186     log_debug(handshake)("Threads signaled, begin processing blocked threads by VMThtread");
 187     const jlong start_time = os::elapsed_counter();
 188     int number_of_threads_completed = 0;
 189     do {
 190       // Check if handshake operation has timed out
 191       if (handshake_has_timed_out(start_time)) {
 192         handle_timeout();
 193       }
 194 
 195       // Have VM thread perform the handshake operation for blocked threads.
 196       // Observing a blocked state may of course be transient but the processing is guarded
 197       // by semaphores and we optimistically begin by working on the blocked threads
 198       {
 199           // We need to re-think this with SMR ThreadsList.
 200           // There is assumption in code that Threads_lock should be lock
 201           // during certain phases.
 202           MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
 203           for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thr = jtiwh.next(); ) {
 204             // A new thread on the ThreadsList will not have an operation.
 205             // Hence is skipped in handshake_process_by_vmthread.
 206             thr->handshake_process_by_vmthread();
 207           }
 208       }
 209 
 210       while (poll_for_completed_thread()) {
 211         // Includes canceled operations by exiting threads.
 212         number_of_threads_completed++;
 213       }
 214 
 215     } while (number_of_threads_issued != number_of_threads_completed);
 216   }
 217 
 218   VMOp_Type type() const { return VMOp_HandshakeAllThreads; }
 219 };
 220 
 221 class VM_HandshakeFallbackOperation : public VM_Operation {
 222   ThreadClosure* _thread_cl;
 223   Thread* _target_thread;
 224   bool _all_threads;
 225   bool _thread_alive;




 120         _thread_alive = true;
 121       }
 122     }
 123 
 124     if (!_thread_alive) {
 125       return;
 126     }
 127 
 128     if (!UseMembar) {
 129       os::serialize_thread_states();
 130     }
 131 
 132     log_trace(handshake)("Thread signaled, begin processing by VMThtread");
 133     jlong start_time = os::elapsed_counter();
 134     do {
 135       if (handshake_has_timed_out(start_time)) {
 136         handle_timeout();
 137       }
 138 
 139       // We need to re-think this with SMR ThreadsList.
 140       // There is an assumption in the code that the Threads_lock should be
 141       // locked during certain phases.
 142       MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
 143       ThreadsListHandle tlh;
 144       if (tlh.includes(_target)) {
 145         // Warning _target's address might be re-used.
 146         // handshake_process_by_vmthread will check the semaphore for us again.
 147         // Since we can't have more then one handshake in flight a reuse of
 148         // _target's address should be okay since the new thread will not have
 149         // an operation.
 150         _target->handshake_process_by_vmthread();
 151       } else {
 152         // We can't warn here since the thread does cancel_handshake after
 153         // it has been removed from the ThreadsList. So we should just keep
 154         // looping here until while below returns false. If we have a bug,
 155         // then we hang here, which is good for debugging.
 156       }

 157     } while (!poll_for_completed_thread());
 158   }
 159 
 160   VMOp_Type type() const { return VMOp_HandshakeOneThread; }
 161 
 162   bool thread_alive() const { return _thread_alive; }
 163 };
 164 
 165 class VM_HandshakeAllThreads: public VM_Handshake {
 166  public:
 167   VM_HandshakeAllThreads(HandshakeThreadsOperation* op) : VM_Handshake(op) {}
 168 
 169   void doit() {
 170     TraceTime timer("Performing operation (vmoperation doit)", TRACETIME_LOG(Info, handshake));
 171 
 172     int number_of_threads_issued = 0;
 173     for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thr = jtiwh.next(); ) {
 174       set_handshake(thr);
 175       number_of_threads_issued++;
 176     }


 181     }
 182 
 183     if (!UseMembar) {
 184       os::serialize_thread_states();
 185     }
 186 
 187     log_debug(handshake)("Threads signaled, begin processing blocked threads by VMThtread");
 188     const jlong start_time = os::elapsed_counter();
 189     int number_of_threads_completed = 0;
 190     do {
 191       // Check if handshake operation has timed out
 192       if (handshake_has_timed_out(start_time)) {
 193         handle_timeout();
 194       }
 195 
 196       // Have VM thread perform the handshake operation for blocked threads.
 197       // Observing a blocked state may of course be transient but the processing is guarded
 198       // by semaphores and we optimistically begin by working on the blocked threads
 199       {
 200           // We need to re-think this with SMR ThreadsList.
 201           // There is an assumption in the code that the Threads_lock should
 202           // be locked during certain phases.
 203           MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
 204           for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thr = jtiwh.next(); ) {
 205             // A new thread on the ThreadsList will not have an operation,
 206             // hence it is skipped in handshake_process_by_vmthread.
 207             thr->handshake_process_by_vmthread();
 208           }
 209       }
 210 
 211       while (poll_for_completed_thread()) {
 212         // Includes canceled operations by exiting threads.
 213         number_of_threads_completed++;
 214       }
 215 
 216     } while (number_of_threads_issued != number_of_threads_completed);
 217   }
 218 
 219   VMOp_Type type() const { return VMOp_HandshakeAllThreads; }
 220 };
 221 
 222 class VM_HandshakeFallbackOperation : public VM_Operation {
 223   ThreadClosure* _thread_cl;
 224   Thread* _target_thread;
 225   bool _all_threads;
 226   bool _thread_alive;


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