c_WaitableWaitHandle* AsioContext::getBlamedWaitHandle() {
// first let's try to find wait handle, responsible for wakeup
auto session = AsioSession::Get();
auto ete_queue = session->getExternalThreadEventQueue();
c_ExternalThreadEventWaitHandle* ewh = ete_queue->lastReceived();
if (ewh != nullptr &&
ewh->getContextIdx() == session->getCurrentContextIdx()) {
return ewh;
}
// may return cancelled wait handle, which no longer has contextIdx
c_SleepWaitHandle* swh = session->nextSleepEvent();
if (swh != nullptr && !swh->isFinished() &&
swh->getContextIdx() == session->getCurrentContextIdx() &&
swh->getWakeTime() <= AsioSession::TimePoint::clock::now()) {
return swh;
}
// not found? let's find a wait handle from current context to blame
if (!m_externalThreadEvents.empty()) {
return m_externalThreadEvents[0];
}
if (!m_sleepEvents.empty()) {
return m_sleepEvents[0];
}
return nullptr;
}
void AsioContext::runUntil(c_WaitableWaitHandle* wait_handle) {
assert(!m_current);
assert(wait_handle);
assert(wait_handle->getContext() == this);
auto session = AsioSession::Get();
uint8_t check_ete_counter = 0;
if (!session->hasAbruptInterruptException()) {
session->initAbruptInterruptException();
}
while (!wait_handle->isFinished()) {
// process ready external thread events once per 256 other events
// (when 8-bit check_ete_counter overflows)
if (!++check_ete_counter) {
// queue may contain received unprocessed events from failed runUntil()
auto queue = session->getExternalThreadEventQueue();
if (UNLIKELY(queue->hasReceived()) || queue->tryReceiveSome()) {
queue->processAllReceived();
}
}
// run queue of ready continuations once
if (!m_runnableQueue.empty()) {
auto current = m_runnableQueue.front();
m_runnableQueue.pop();
m_current = current;
auto exit_guard = folly::makeGuard([&] {
m_current = nullptr;
decRefObj(current);
});
m_current->run();
continue;
}
// run default priority queue once
if (runSingle(m_priorityQueueDefault)) {
continue;
}
// pending external thread events? wait for at least one to become ready
if (!m_externalThreadEvents.empty()) {
// queue may contain received unprocessed events from failed runUntil()
auto queue = session->getExternalThreadEventQueue();
if (LIKELY(!queue->hasReceived())) {
// all your wait time are belong to us
queue->receiveSome();
}
queue->processAllReceived();
continue;
}
// run no-pending-io priority queue once
if (runSingle(m_priorityQueueNoPendingIO)) {
continue;
}
// What? The wait handle did not finish? We know it is part of the current
// context and since there is nothing else to run, it cannot be in RUNNING
// or SCHEDULED state. So it must be BLOCKED on something. Apparently, the
// same logic can be used recursively on the something, so there is an
// infinite chain of blocked wait handles. But our memory is not infinite.
// What could it possibly mean? I think we are in a deep sh^H^Hcycle.
// But we can't, the cycles are detected and avoided at blockOn() time.
// So, looks like it's not cycle, but the word I started typing first.
assert(false);
throw FatalErrorException(
"Invariant violation: queues are empty, but wait handle did not finish");
}
}
void AsioContext::runUntil(c_WaitableWaitHandle* wait_handle) {
assert(wait_handle);
assert(wait_handle->getContext() == this);
auto session = AsioSession::Get();
auto ete_queue = session->getExternalThreadEventQueue();
auto& sleep_queue = session->getSleepEventQueue();
if (!session->hasAbruptInterruptException()) {
session->initAbruptInterruptException();
}
while (!wait_handle->isFinished()) {
// Run queue of ready async functions once.
if (!m_runnableQueue.empty()) {
auto current = m_runnableQueue.back();
m_runnableQueue.pop_back();
current->resume();
continue;
}
// Process all sleep handles that have completed their sleep.
if (session->processSleepEvents()) {
continue;
}
// Process all external thread events that have completed their operation.
// Queue may contain received unprocessed events from failed runUntil().
if (UNLIKELY(ete_queue->hasReceived()) || ete_queue->tryReceiveSome()) {
ete_queue->processAllReceived();
continue;
}
// Run default priority queue once.
if (runSingle(m_priorityQueueDefault)) {
continue;
}
// Wait for pending external thread events...
if (!m_externalThreadEvents.empty()) {
// ...but only until the next sleeper (from any context) finishes.
AsioSession::TimePoint waketime;
if (sleep_queue.empty()) {
waketime = AsioSession::getLatestWakeTime();
} else {
waketime = sleep_queue.top()->getWakeTime();
}
// Wait if necessary.
if (LIKELY(!ete_queue->hasReceived())) {
onIOWaitEnter(session);
ete_queue->receiveSomeUntil(waketime);
onIOWaitExit(session);
}
if (ete_queue->hasReceived()) {
// Either we didn't have to wait, or we waited but no sleeper timed us
// out, so just handle the ETEs.
ete_queue->processAllReceived();
} else {
// No received events means the next-to-wake sleeper timed us out.
session->processSleepEvents();
}
continue;
}
// If we're here, then the only things left are sleepers. Wait for one to
// be ready (in any context).
if (!m_sleepEvents.empty()) {
onIOWaitEnter(session);
std::this_thread::sleep_until(sleep_queue.top()->getWakeTime());
onIOWaitExit(session);
session->processSleepEvents();
continue;
}
// Run no-pending-io priority queue once.
if (runSingle(m_priorityQueueNoPendingIO)) {
continue;
}
// What? The wait handle did not finish? We know it is part of the current
// context and since there is nothing else to run, it cannot be in RUNNING
// or SCHEDULED state. So it must be BLOCKED on something. Apparently, the
// same logic can be used recursively on the something, so there is an
// infinite chain of blocked wait handles. But our memory is not infinite.
// What could it possibly mean? I think we are in a deep sh^H^Hcycle.
// But we can't, the cycles are detected and avoided at blockOn() time.
// So, looks like it's not cycle, but the word I started typing first.
assert(false);
throw FatalErrorException(
"Invariant violation: queues are empty, but wait handle did not finish");
}
}
