/*

 * Copyright (c) 2017, 2019, 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/atomic.hpp"

#include "runtime/handshake.hpp"

#include "runtime/interfaceSupport.inline.hpp"

#include "runtime/osThread.hpp"

#include "runtime/semaphore.inline.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"

class HandshakeOperation: public StackObj {

public:

  virtual void do_handshake(JavaThread* thread) = 0;

};

class HandshakeThreadsOperation: public HandshakeOperation {

  static Semaphore _done;

  ThreadClosure* _thread_cl;

  bool _executed;

public:

  HandshakeThreadsOperation(ThreadClosure* cl) : _thread_cl(cl), _executed(false) {}

  void do_handshake(JavaThread* thread);

  bool thread_has_completed() { return _done.trywait(); }

  bool executed() const { return _executed; }

#ifdef ASSERT

  void check_state() {

    assert(!_done.trywait(), "Must be zero");

  }

#endif

};

Semaphore HandshakeThreadsOperation::_done(0);

class VM_Handshake: public VM_Operation {

  const jlong _handshake_timeout;

 public:

  bool evaluate_at_safepoint() const { return false; }

 protected:

  HandshakeThreadsOperation* const _op;

  VM_Handshake(HandshakeThreadsOperation* op) :

      _handshake_timeout(TimeHelper::millis_to_counter(HandshakeTimeout)), _op(op) {}

  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;

  for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thr = jtiwh.next(); ) {

    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;

 public:

  VM_HandshakeOneThread(HandshakeThreadsOperation* op, JavaThread* target) :

    VM_Handshake(op), _target(target) {}

  void doit() {

    DEBUG_ONLY(_op->check_state();)

    TraceTime timer("Finished executing single-target operation (VM_HandshakeOneThread::doit)", TRACETIME_LOG(Info, handshake));

    ThreadsListHandle tlh;

    if (tlh.includes(_target)) {

      set_handshake(_target);

    } else {

      log_trace(handshake)("JavaThread " INTPTR_FORMAT " is not alive", p2i(_target));

      return;

    }

    log_trace(handshake)("JavaThread " INTPTR_FORMAT " signaled, begin attempt to process by VMThtread", p2i(_target));

    jlong start_time = os::elapsed_counter();

    do {

      if (handshake_has_timed_out(start_time)) {

        handle_timeout();

      }

      // We need to re-think this with SMR ThreadsList.

      // There is an assumption in the code that the Threads_lock should be

      // locked during certain phases.

      {

        MutexLocker ml(Threads_lock);

        _target->handshake_process_by_vmthread();

      }

    } while (!poll_for_completed_thread());

    DEBUG_ONLY(_op->check_state();)

  }

  VMOp_Type type() const { return VMOp_HandshakeOneThread; }

  bool executed() const { return _op->executed(); }

};

class VM_HandshakeAllThreads: public VM_Handshake {

 public:

  VM_HandshakeAllThreads(HandshakeThreadsOperation* op) : VM_Handshake(op) {}

  void doit() {

    DEBUG_ONLY(_op->check_state();)

    TraceTime timer("Finished executing multi-target operation (VM_HandshakeAllThreads::doit)", TRACETIME_LOG(Info, handshake));

    JavaThreadIteratorWithHandle jtiwh;

    int number_of_threads_issued = 0;

    for (JavaThread *thr = jtiwh.next(); thr != NULL; thr = jtiwh.next()) {

      set_handshake(thr);

      number_of_threads_issued++;

    }

    if (number_of_threads_issued < 1) {

      log_debug(handshake)("No threads to handshake.");

      return;

    }

    log_debug(handshake)("Threads signaled, begin processing blocked threads by VMThtread");

    const jlong start_time = os::elapsed_counter();

    int number_of_threads_completed = 0;

    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

      {

          // We need to re-think this with SMR ThreadsList.

          // There is an assumption in the code that the Threads_lock should

          // be locked during certain phases.

          jtiwh.rewind();

          MutexLocker ml(Threads_lock);

          for (JavaThread *thr = jtiwh.next(); thr != NULL; thr = jtiwh.next()) {

            // A new thread on the ThreadsList will not have an operation,

            // hence it is skipped in handshake_process_by_vmthread.

            thr->handshake_process_by_vmthread();

          }

      }

      while (poll_for_completed_thread()) {

        // Includes canceled operations by exiting threads.

        number_of_threads_completed++;

      }

    } while (number_of_threads_issued > number_of_threads_completed);

    assert(number_of_threads_issued == number_of_threads_completed, "Must be the same");

    DEBUG_ONLY(_op->check_state();)

  }

  VMOp_Type type() const { return VMOp_HandshakeAllThreads; }

};

class VM_HandshakeFallbackOperation : public VM_Operation {

  ThreadClosure* _thread_cl;

  Thread* _target_thread;

  bool _all_threads;

  bool _executed;

public:

  VM_HandshakeFallbackOperation(ThreadClosure* cl) :

      _thread_cl(cl), _target_thread(NULL), _all_threads(true), _executed(false) {}

  VM_HandshakeFallbackOperation(ThreadClosure* cl, Thread* target) :

      _thread_cl(cl), _target_thread(target), _all_threads(false), _executed(false) {}

  void doit() {

    log_trace(handshake)("VMThread executing VM_HandshakeFallbackOperation");

    for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {

      if (_all_threads || t == _target_thread) {

        if (t == _target_thread) {

          _executed = true;

        }

        _thread_cl->do_thread(t);

      }

    }

  }

  VMOp_Type type() const { return VMOp_HandshakeFallback; }

  bool executed() const { return _executed; }

};

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));

  // Only actually execute the operation for non terminated threads.

  if (!thread->is_terminated()) {

    _thread_cl->do_thread(thread);

    _executed = true;

  }

  // 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.executed();

  } else {

    VM_HandshakeFallbackOperation op(thread_cl, target);

    VMThread::execute(&op);

    return op.executed();

  }

}

HandshakeState::HandshakeState() : _operation(NULL), _semaphore(1), _thread_in_process_handshake(false) {}

void HandshakeState::set_operation(JavaThread* target, HandshakeOperation* op) {

  _operation = op;

  SafepointMechanism::arm_local_poll_release(target);

}

void HandshakeState::clear_handshake(JavaThread* target) {

  _operation = NULL;

  SafepointMechanism::disarm_if_needed(target, true /* release */);

}

void HandshakeState::process_self_inner(JavaThread* thread) {

  assert(Thread::current() == thread, "should call from thread");

  assert(!thread->is_terminated(), "should not be a terminated thread");

  assert(thread->thread_state() != _thread_blocked, "should not be in a blocked state");

  assert(thread->thread_state() != _thread_in_native, "should not be in native");

  do {

    ThreadInVMForHandshake tivm(thread);

    if (!_semaphore.trywait()) {

      _semaphore.wait_with_safepoint_check(thread);

    }

    HandshakeOperation* op = Atomic::load_acquire(&_operation);

    if (op != NULL) {

      HandleMark hm(thread);

      CautiouslyPreserveExceptionMark pem(thread);

      // Disarm before execute the operation

      clear_handshake(thread);

      op->do_handshake(thread);

    }

    _semaphore.signal();

  } while (has_operation());

}

bool HandshakeState::vmthread_can_process_handshake(JavaThread* target) {

  // handshake_safe may only be called with polls armed.

  // VM thread controls this by first claiming the handshake via claim_handshake_for_vmthread.

  return SafepointSynchronize::handshake_safe(target);

}

static bool possibly_vmthread_can_process_handshake(JavaThread* target) {

  // An externally suspended thread cannot be resumed while the

  // Threads_lock is held so it is safe.

  // Note that this method is allowed to produce false positives.

  assert(Threads_lock->owned_by_self(), "Not holding Threads_lock.");

  if (target->is_ext_suspended()) {

    return true;

  }

  if (target->is_terminated()) {

    return true;

  }

  switch (target->thread_state()) {

  case _thread_in_native:

    // native threads are safe if they have no java stack or have walkable stack

    return !target->has_last_Java_frame() || target->frame_anchor()->walkable();

  case _thread_blocked:

    return true;

  default:

    return false;

  }

}

bool HandshakeState::claim_handshake_for_vmthread() {

  if (!_semaphore.trywait()) {

    return false;

  }

  if (has_operation()) {

    return true;

  }

  _semaphore.signal();

  return false;

}

void HandshakeState::process_by_vmthread(JavaThread* target) {

  assert(Thread::current()->is_VM_thread(), "should call from vm thread");

  // Threads_lock must be held here, but that is assert()ed in

  // possibly_vmthread_can_process_handshake().

  if (!has_operation()) {

    // JT has already cleared its handshake

    return;

  }

  if (!possibly_vmthread_can_process_handshake(target)) {

    // JT is observed in an unsafe state, it must notice the handshake itself

    return;

  }

  // Claim the semaphore if there still an operation to be executed.

  if (!claim_handshake_for_vmthread()) {

    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 (vmthread_can_process_handshake(target)) {

    guarantee(!_semaphore.trywait(), "we should already own the semaphore");

    log_trace(handshake)("Processing handshake by VMThtread");

    _operation->do_handshake(target);

    // Disarm after VM thread have executed the operation.

    clear_handshake(target);

    // Release the thread

  }

  _semaphore.signal();

}