src/hotspot/share/runtime/safepointMechanism.inline.hpp

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#ifndef SHARE_RUNTIME_SAFEPOINTMECHANISM_INLINE_HPP
#define SHARE_RUNTIME_SAFEPOINTMECHANISM_INLINE_HPP

#include "runtime/safepointMechanism.hpp"

#include "runtime/atomic.hpp"
#include "runtime/handshake.hpp"
#include "runtime/safepoint.hpp"
#include "runtime/stackWatermarkSet.hpp"

// Caller is responsible for using a memory barrier if needed.
inline void SafepointMechanism::ThreadData::set_polling_page(uintptr_t poll_value) {
  Atomic::store(&_polling_page, poll_value);
}

// Caller is responsible for using a memory barrier if needed.
inline void SafepointMechanism::ThreadData::set_polling_word(uintptr_t poll_value) {
  Atomic::store(&_polling_word, poll_value);
}

// The acquire makes sure reading of polling page is done before
// the reading the handshake operation or the global state
inline uintptr_t SafepointMechanism::ThreadData::get_polling_word() {
  return Atomic::load_acquire(&_polling_word);
}

bool SafepointMechanism::local_poll_armed(JavaThread* thread) {
  return thread->poll_data()->get_polling_word() & poll_bit();
}

bool SafepointMechanism::global_poll() {
  return (SafepointSynchronize::_state != SafepointSynchronize::_not_synchronized);
}

bool SafepointMechanism::should_process(JavaThread* thread, bool allow_suspend) {
  if (!local_poll_armed(thread)) {
    return false;
  }

  if (global_poll() || // Safepoint
      thread->handshake_state()->has_operation(allow_suspend, false /* check_async_exception */) || // Handshake
      !StackWatermarkSet::processing_started(thread)) { // StackWatermark processing is not started
    return true;
  }

  // It has boiled down to two possibilities:
  // 1: We have nothing to process, this just a disarm poll.
  // 2: We have a suspend or async exception handshake, which cannot be processed.
  // We update the poll value in case of a disarm, to reduce false positives.
  update_poll_values(thread);
  return false;
}

void SafepointMechanism::process_if_requested(JavaThread* thread, bool allow_suspend, bool check_async_exception) {
  // Check NoSafepointVerifier. This also clears unhandled oops if CheckUnhandledOops is used.
  thread->check_possible_safepoint();

  if (local_poll_armed(thread)) {
    process(thread, allow_suspend, check_async_exception);
  }
}

void SafepointMechanism::process_if_requested_with_exit_check(JavaThread* thread, bool check_async_exception) {
  process_if_requested(thread, true /* allow_suspend */, check_async_exception);
  if (thread->has_special_runtime_exit_condition()) {
    thread->handle_special_runtime_exit_condition();
  }
}

void SafepointMechanism::arm_local_poll(JavaThread* thread) {
  thread->poll_data()->set_polling_word(_poll_word_armed_value);
  thread->poll_data()->set_polling_page(_poll_page_armed_value);
}

void SafepointMechanism::disarm_local_poll(JavaThread* thread) {
  thread->poll_data()->set_polling_word(_poll_word_disarmed_value);
  thread->poll_data()->set_polling_page(_poll_page_disarmed_value);
}

void SafepointMechanism::arm_local_poll_release(JavaThread* thread) {
  OrderAccess::release();
  thread->poll_data()->set_polling_word(_poll_word_armed_value);
  thread->poll_data()->set_polling_page(_poll_page_armed_value);
}

#endif // SHARE_RUNTIME_SAFEPOINTMECHANISM_INLINE_HPP