--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/runtime/handshake.cpp Thu Aug 31 10:00:28 2017 +0200
@@ -0,0 +1,352 @@
+/*
+ * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "logging/log.hpp"
+#include "logging/logStream.hpp"
+#include "memory/resourceArea.hpp"
+#include "runtime/handshake.hpp"
+#include "runtime/interfaceSupport.hpp"
+#include "runtime/osThread.hpp"
+#include "runtime/semaphore.hpp"
+#include "runtime/task.hpp"
+#include "runtime/timerTrace.hpp"
+#include "runtime/thread.hpp"
+#include "runtime/vmThread.hpp"
+#include "utilities/formatBuffer.hpp"
+#include "utilities/preserveException.hpp"
+
+#define ALL_JAVA_THREADS(X) for (JavaThread* X = Threads::first(); X; X = X->next())
+
+class HandshakeOperation: public StackObj {
+public:
+ virtual void do_handshake(JavaThread* thread) = 0;
+ virtual void cancel_handshake(JavaThread* thread) = 0;
+};
+
+class HandshakeThreadsOperation: public HandshakeOperation {
+ Semaphore _done;
+ ThreadClosure* _thread_cl;
+
+public:
+ HandshakeThreadsOperation(ThreadClosure* cl) : _done(0), _thread_cl(cl) {}
+ void do_handshake(JavaThread* thread);
+ void cancel_handshake(JavaThread* thread) { _done.signal(); };
+
+ bool thread_has_completed() { return _done.trywait(); }
+};
+
+class VM_Handshake: public VM_Operation {
+ HandshakeThreadsOperation* const _op;
+ const jlong _handshake_timeout;
+ public:
+ bool evaluate_at_safepoint() const { return false; }
+
+ bool evaluate_concurrently() const { return false; }
+
+ protected:
+
+ VM_Handshake(HandshakeThreadsOperation* op) :
+ _op(op),
+ _handshake_timeout(TimeHelper::millis_to_counter(HandshakeTimeout)) {}
+
+ void set_handshake(JavaThread* target) {
+ target->set_handshake_operation(_op);
+ }
+
+ // This method returns true for threads completed their operation
+ // and true for threads canceled their operation.
+ // A cancellation can happen if the thread is exiting.
+ bool poll_for_completed_thread() { return _op->thread_has_completed(); }
+
+ bool handshake_has_timed_out(jlong start_time);
+ static void handle_timeout();
+};
+
+bool VM_Handshake::handshake_has_timed_out(jlong start_time) {
+ // Check if handshake operation has timed out
+ if (_handshake_timeout > 0) {
+ return os::elapsed_counter() >= (start_time + _handshake_timeout);
+ }
+ return false;
+}
+
+void VM_Handshake::handle_timeout() {
+ LogStreamHandle(Warning, handshake) log_stream;
+ MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
+ ALL_JAVA_THREADS(thr) {
+ if (thr->has_handshake()) {
+ log_stream.print("Thread " PTR_FORMAT " has not cleared its handshake op", p2i(thr));
+ thr->print_thread_state_on(&log_stream);
+ }
+ }
+ log_stream.flush();
+ fatal("Handshake operation timed out");
+}
+
+
+class VM_HandshakeOneThread: public VM_Handshake {
+ JavaThread* _target;
+ bool _thread_alive;
+ public:
+ VM_HandshakeOneThread(HandshakeThreadsOperation* op, JavaThread* target) :
+ VM_Handshake(op), _target(target), _thread_alive(false) {}
+
+ void doit() {
+ TraceTime timer("Performing single-target operation (vmoperation doit)", TRACETIME_LOG(Info, handshake));
+
+ {
+ MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
+ if (Threads::includes(_target)) {
+ set_handshake(_target);
+ _thread_alive = true;
+ }
+ }
+
+ if (!_thread_alive) {
+ return;
+ }
+
+ if (!UseMembar) {
+ os::serialize_thread_states();
+ }
+
+ log_trace(handshake)("Thread signaled, begin processing by VMThtread");
+ jlong start_time = os::elapsed_counter();
+ do {
+ if (handshake_has_timed_out(start_time)) {
+ handle_timeout();
+ }
+
+ MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
+ _target->handshake_process_by_vmthread();
+
+ } while (!poll_for_completed_thread());
+ }
+
+ VMOp_Type type() const { return VMOp_HandshakeOneThread; }
+
+ bool thread_alive() const { return _thread_alive; }
+};
+
+class VM_HandshakeAllThreads: public VM_Handshake {
+ public:
+ VM_HandshakeAllThreads(HandshakeThreadsOperation* op) : VM_Handshake(op) {}
+
+ void doit() {
+ TraceTime timer("Performing operation (vmoperation doit)", TRACETIME_LOG(Info, handshake));
+
+ int number_of_threads_issued = -1;
+ int number_of_threads_completed = 0;
+ {
+ MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
+ number_of_threads_issued = Threads::number_of_threads();
+
+ ALL_JAVA_THREADS(thr) {
+ set_handshake(thr);
+ }
+ }
+
+ if (!UseMembar) {
+ os::serialize_thread_states();
+ }
+
+ log_debug(handshake)("Threads signaled, begin processing blocked threads by VMThtread");
+ const jlong start_time = os::elapsed_counter();
+ do {
+ // Check if handshake operation has timed out
+ if (handshake_has_timed_out(start_time)) {
+ handle_timeout();
+ }
+
+ // Have VM thread perform the handshake operation for blocked threads.
+ // Observing a blocked state may of course be transient but the processing is guarded
+ // by semaphores and we optimistically begin by working on the blocked threads
+ {
+ MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
+ ALL_JAVA_THREADS(thr) {
+ thr->handshake_process_by_vmthread();
+ }
+ }
+
+ while (poll_for_completed_thread()) {
+ number_of_threads_completed++;
+ }
+
+ } while (number_of_threads_issued != number_of_threads_completed);
+ }
+
+ VMOp_Type type() const { return VMOp_HandshakeAllThreads; }
+};
+
+class VM_HandshakeFallbackOperation : public VM_Operation {
+ ThreadClosure* _thread_cl;
+ Thread* _target_thread;
+ bool _all_threads;
+ bool _thread_alive;
+public:
+ VM_HandshakeFallbackOperation(ThreadClosure* cl) :
+ _thread_cl(cl), _target_thread(NULL), _all_threads(true), _thread_alive(true) {}
+ VM_HandshakeFallbackOperation(ThreadClosure* cl, Thread* target) :
+ _thread_cl(cl), _target_thread(target), _all_threads(false), _thread_alive(false) {}
+
+ void doit() {
+ ALL_JAVA_THREADS(t) {
+ if (_all_threads || t == _target_thread) {
+ if (t == _target_thread) {
+ _thread_alive = true;
+ }
+ _thread_cl->do_thread(t);
+ }
+ }
+ }
+
+ VMOp_Type type() const { return VMOp_HandshakeFallback; }
+ bool thread_alive() const { return _thread_alive; }
+};
+
+#undef ALL_JAVA_THREADS
+
+void HandshakeThreadsOperation::do_handshake(JavaThread* thread) {
+ ResourceMark rm;
+ FormatBufferResource message("Operation for thread " PTR_FORMAT ", is_vm_thread: %s",
+ p2i(thread), BOOL_TO_STR(Thread::current()->is_VM_thread()));
+ TraceTime timer(message, TRACETIME_LOG(Debug, handshake, task));
+ _thread_cl->do_thread(thread);
+
+ // Use the semaphore to inform the VM thread that we have completed the operation
+ _done.signal();
+}
+
+void Handshake::execute(ThreadClosure* thread_cl) {
+ if (ThreadLocalHandshakes) {
+ HandshakeThreadsOperation cto(thread_cl);
+ VM_HandshakeAllThreads handshake(&cto);
+ VMThread::execute(&handshake);
+ } else {
+ VM_HandshakeFallbackOperation op(thread_cl);
+ VMThread::execute(&op);
+ }
+}
+
+bool Handshake::execute(ThreadClosure* thread_cl, JavaThread* target) {
+ if (ThreadLocalHandshakes) {
+ HandshakeThreadsOperation cto(thread_cl);
+ VM_HandshakeOneThread handshake(&cto, target);
+ VMThread::execute(&handshake);
+ return handshake.thread_alive();
+ } else {
+ VM_HandshakeFallbackOperation op(thread_cl, target);
+ VMThread::execute(&op);
+ return op.thread_alive();
+ }
+}
+
+HandshakeState::HandshakeState() : _operation(NULL), _semaphore(1), _vmthread_holds_semaphore(false), _thread_in_process_handshake(false) {}
+
+void HandshakeState::set_operation(JavaThread* target, HandshakeOperation* op) {
+ _operation = op;
+ SafepointMechanism::arm_local_poll(target);
+}
+
+void HandshakeState::clear_handshake(JavaThread* target) {
+ _operation = NULL;
+ SafepointMechanism::disarm_local_poll(target);
+}
+
+void HandshakeState::process_self_inner(JavaThread* thread) {
+ assert(Thread::current() == thread, "should call from thread");
+ CautiouslyPreserveExceptionMark pem(thread);
+ ThreadInVMForHandshake tivm(thread);
+ if (!_semaphore.trywait()) {
+ ThreadBlockInVM tbivm(thread);
+ _semaphore.wait();
+ }
+ if (has_operation()) {
+ HandshakeOperation* op = _operation;
+ clear_handshake(thread);
+ if (op != NULL) {
+ op->do_handshake(thread);
+ }
+ }
+ _semaphore.signal();
+}
+
+void HandshakeState::cancel_inner(JavaThread* thread) {
+ assert(Thread::current() == thread, "should call from thread");
+ assert(thread->thread_state() == _thread_in_vm, "must be in vm state");
+#ifdef DEBUG
+ {
+ MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
+ assert(!Threads::includes(thread), "java thread must not be on threads list");
+ }
+#endif
+ HandshakeOperation* op = _operation;
+ clear_handshake(thread);
+ if (op != NULL) {
+ op->cancel_handshake(thread);
+ }
+}
+
+bool HandshakeState::vmthread_can_process_handshake(JavaThread* target) {
+ return SafepointSynchronize::safepoint_safe(target, target->thread_state());
+}
+
+bool HandshakeState::claim_handshake_for_vmthread() {
+ if (_semaphore.trywait()) {
+ if (has_operation()) {
+ _vmthread_holds_semaphore = true;
+ } else {
+ _semaphore.signal();
+ }
+ }
+ return _vmthread_holds_semaphore;
+}
+
+void HandshakeState::process_by_vmthread(JavaThread* target) {
+ assert(Thread::current()->is_VM_thread(), "should call from vm thread");
+
+ if (!has_operation()) {
+ // JT has already cleared its handshake
+ return;
+ }
+
+ if (!vmthread_can_process_handshake(target)) {
+ // JT is observed in an unsafe state, it must notice the handshake itself
+ return;
+ }
+
+ // If we own the semaphore at this point and while owning the semaphore
+ // can observe a safe state the thread cannot possibly continue without
+ // getting caught by the semaphore.
+ if (claim_handshake_for_vmthread() && vmthread_can_process_handshake(target)) {
+ guarantee(!_semaphore.trywait(), "we should already own the semaphore");
+
+ _operation->do_handshake(target);
+ clear_handshake(target);
+ _vmthread_holds_semaphore = false;
+ // Release the thread
+ _semaphore.signal();
+ }
+}