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/*
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* Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*
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*/
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#include "precompiled.hpp"
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#include "logging/log.hpp"
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#include "logging/logStream.hpp"
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#include "memory/resourceArea.hpp"
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#include "runtime/handshake.hpp"
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#include "runtime/interfaceSupport.hpp"
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#include "runtime/osThread.hpp"
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#include "runtime/semaphore.hpp"
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#include "runtime/task.hpp"
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#include "runtime/timerTrace.hpp"
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#include "runtime/thread.hpp"
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#include "runtime/vmThread.hpp"
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#include "utilities/formatBuffer.hpp"
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#include "utilities/preserveException.hpp"
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#define ALL_JAVA_THREADS(X) for (JavaThread* X = Threads::first(); X; X = X->next())
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class HandshakeOperation: public StackObj {
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public:
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virtual void do_handshake(JavaThread* thread) = 0;
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virtual void cancel_handshake(JavaThread* thread) = 0;
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};
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class HandshakeThreadsOperation: public HandshakeOperation {
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Semaphore _done;
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ThreadClosure* _thread_cl;
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public:
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HandshakeThreadsOperation(ThreadClosure* cl) : _done(0), _thread_cl(cl) {}
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void do_handshake(JavaThread* thread);
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void cancel_handshake(JavaThread* thread) { _done.signal(); };
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bool thread_has_completed() { return _done.trywait(); }
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};
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class VM_Handshake: public VM_Operation {
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HandshakeThreadsOperation* const _op;
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const jlong _handshake_timeout;
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public:
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bool evaluate_at_safepoint() const { return false; }
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bool evaluate_concurrently() const { return false; }
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protected:
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VM_Handshake(HandshakeThreadsOperation* op) :
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_op(op),
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_handshake_timeout(TimeHelper::millis_to_counter(HandshakeTimeout)) {}
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void set_handshake(JavaThread* target) {
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target->set_handshake_operation(_op);
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}
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// This method returns true for threads completed their operation
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// and true for threads canceled their operation.
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// A cancellation can happen if the thread is exiting.
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bool poll_for_completed_thread() { return _op->thread_has_completed(); }
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bool handshake_has_timed_out(jlong start_time);
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static void handle_timeout();
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};
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bool VM_Handshake::handshake_has_timed_out(jlong start_time) {
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// Check if handshake operation has timed out
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if (_handshake_timeout > 0) {
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return os::elapsed_counter() >= (start_time + _handshake_timeout);
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}
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return false;
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}
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void VM_Handshake::handle_timeout() {
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LogStreamHandle(Warning, handshake) log_stream;
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MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
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ALL_JAVA_THREADS(thr) {
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if (thr->has_handshake()) {
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log_stream.print("Thread " PTR_FORMAT " has not cleared its handshake op", p2i(thr));
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thr->print_thread_state_on(&log_stream);
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}
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}
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log_stream.flush();
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fatal("Handshake operation timed out");
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}
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class VM_HandshakeOneThread: public VM_Handshake {
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JavaThread* _target;
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bool _thread_alive;
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public:
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VM_HandshakeOneThread(HandshakeThreadsOperation* op, JavaThread* target) :
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VM_Handshake(op), _target(target), _thread_alive(false) {}
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void doit() {
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TraceTime timer("Performing single-target operation (vmoperation doit)", TRACETIME_LOG(Info, handshake));
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{
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MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
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if (Threads::includes(_target)) {
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set_handshake(_target);
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_thread_alive = true;
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}
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}
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if (!_thread_alive) {
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return;
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}
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if (!UseMembar) {
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os::serialize_thread_states();
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}
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log_trace(handshake)("Thread signaled, begin processing by VMThtread");
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jlong start_time = os::elapsed_counter();
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do {
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if (handshake_has_timed_out(start_time)) {
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handle_timeout();
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}
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MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
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_target->handshake_process_by_vmthread();
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} while (!poll_for_completed_thread());
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}
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VMOp_Type type() const { return VMOp_HandshakeOneThread; }
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bool thread_alive() const { return _thread_alive; }
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};
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class VM_HandshakeAllThreads: public VM_Handshake {
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public:
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VM_HandshakeAllThreads(HandshakeThreadsOperation* op) : VM_Handshake(op) {}
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void doit() {
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TraceTime timer("Performing operation (vmoperation doit)", TRACETIME_LOG(Info, handshake));
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int number_of_threads_issued = -1;
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int number_of_threads_completed = 0;
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{
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MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
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number_of_threads_issued = Threads::number_of_threads();
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ALL_JAVA_THREADS(thr) {
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set_handshake(thr);
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}
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}
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if (!UseMembar) {
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os::serialize_thread_states();
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}
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log_debug(handshake)("Threads signaled, begin processing blocked threads by VMThtread");
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const jlong start_time = os::elapsed_counter();
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do {
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// Check if handshake operation has timed out
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if (handshake_has_timed_out(start_time)) {
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handle_timeout();
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}
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// Have VM thread perform the handshake operation for blocked threads.
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// Observing a blocked state may of course be transient but the processing is guarded
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// by semaphores and we optimistically begin by working on the blocked threads
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{
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MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
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ALL_JAVA_THREADS(thr) {
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thr->handshake_process_by_vmthread();
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}
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}
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while (poll_for_completed_thread()) {
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number_of_threads_completed++;
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}
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} while (number_of_threads_issued != number_of_threads_completed);
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}
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VMOp_Type type() const { return VMOp_HandshakeAllThreads; }
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};
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class VM_HandshakeFallbackOperation : public VM_Operation {
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ThreadClosure* _thread_cl;
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Thread* _target_thread;
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bool _all_threads;
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bool _thread_alive;
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public:
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VM_HandshakeFallbackOperation(ThreadClosure* cl) :
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_thread_cl(cl), _target_thread(NULL), _all_threads(true), _thread_alive(true) {}
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VM_HandshakeFallbackOperation(ThreadClosure* cl, Thread* target) :
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_thread_cl(cl), _target_thread(target), _all_threads(false), _thread_alive(false) {}
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void doit() {
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ALL_JAVA_THREADS(t) {
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if (_all_threads || t == _target_thread) {
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if (t == _target_thread) {
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_thread_alive = true;
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}
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_thread_cl->do_thread(t);
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}
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}
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}
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VMOp_Type type() const { return VMOp_HandshakeFallback; }
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bool thread_alive() const { return _thread_alive; }
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};
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#undef ALL_JAVA_THREADS
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void HandshakeThreadsOperation::do_handshake(JavaThread* thread) {
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ResourceMark rm;
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FormatBufferResource message("Operation for thread " PTR_FORMAT ", is_vm_thread: %s",
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p2i(thread), BOOL_TO_STR(Thread::current()->is_VM_thread()));
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TraceTime timer(message, TRACETIME_LOG(Debug, handshake, task));
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_thread_cl->do_thread(thread);
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// Use the semaphore to inform the VM thread that we have completed the operation
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_done.signal();
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}
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void Handshake::execute(ThreadClosure* thread_cl) {
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if (ThreadLocalHandshakes) {
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HandshakeThreadsOperation cto(thread_cl);
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VM_HandshakeAllThreads handshake(&cto);
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VMThread::execute(&handshake);
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} else {
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VM_HandshakeFallbackOperation op(thread_cl);
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VMThread::execute(&op);
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}
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}
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bool Handshake::execute(ThreadClosure* thread_cl, JavaThread* target) {
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if (ThreadLocalHandshakes) {
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HandshakeThreadsOperation cto(thread_cl);
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VM_HandshakeOneThread handshake(&cto, target);
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VMThread::execute(&handshake);
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return handshake.thread_alive();
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} else {
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VM_HandshakeFallbackOperation op(thread_cl, target);
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VMThread::execute(&op);
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return op.thread_alive();
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}
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}
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HandshakeState::HandshakeState() : _operation(NULL), _semaphore(1), _vmthread_holds_semaphore(false), _thread_in_process_handshake(false) {}
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void HandshakeState::set_operation(JavaThread* target, HandshakeOperation* op) {
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_operation = op;
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SafepointMechanism::arm_local_poll(target);
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}
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void HandshakeState::clear_handshake(JavaThread* target) {
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_operation = NULL;
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SafepointMechanism::disarm_local_poll(target);
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}
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void HandshakeState::process_self_inner(JavaThread* thread) {
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assert(Thread::current() == thread, "should call from thread");
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CautiouslyPreserveExceptionMark pem(thread);
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ThreadInVMForHandshake tivm(thread);
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if (!_semaphore.trywait()) {
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ThreadBlockInVM tbivm(thread);
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_semaphore.wait();
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}
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if (has_operation()) {
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HandshakeOperation* op = _operation;
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clear_handshake(thread);
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if (op != NULL) {
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op->do_handshake(thread);
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}
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}
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_semaphore.signal();
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}
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void HandshakeState::cancel_inner(JavaThread* thread) {
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assert(Thread::current() == thread, "should call from thread");
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assert(thread->thread_state() == _thread_in_vm, "must be in vm state");
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#ifdef DEBUG
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{
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MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
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assert(!Threads::includes(thread), "java thread must not be on threads list");
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}
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#endif
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HandshakeOperation* op = _operation;
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clear_handshake(thread);
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if (op != NULL) {
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op->cancel_handshake(thread);
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}
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}
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bool HandshakeState::vmthread_can_process_handshake(JavaThread* target) {
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return SafepointSynchronize::safepoint_safe(target, target->thread_state());
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}
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bool HandshakeState::claim_handshake_for_vmthread() {
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if (_semaphore.trywait()) {
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if (has_operation()) {
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_vmthread_holds_semaphore = true;
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} else {
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_semaphore.signal();
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}
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}
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return _vmthread_holds_semaphore;
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}
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void HandshakeState::process_by_vmthread(JavaThread* target) {
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assert(Thread::current()->is_VM_thread(), "should call from vm thread");
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if (!has_operation()) {
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// JT has already cleared its handshake
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return;
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}
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if (!vmthread_can_process_handshake(target)) {
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// JT is observed in an unsafe state, it must notice the handshake itself
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return;
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}
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// If we own the semaphore at this point and while owning the semaphore
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// can observe a safe state the thread cannot possibly continue without
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// getting caught by the semaphore.
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if (claim_handshake_for_vmthread() && vmthread_can_process_handshake(target)) {
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guarantee(!_semaphore.trywait(), "we should already own the semaphore");
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_operation->do_handshake(target);
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clear_handshake(target);
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_vmthread_holds_semaphore = false;
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// Release the thread
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_semaphore.signal();
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}
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}
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