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// Copyright (c) 2015-2017 The Starwels developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#include <scheduler.h>
#include <random.h>
#include <reverselock.h>
#include <assert.h>
#include <boost/bind.hpp>
#include <utility>
CScheduler::CScheduler() : nThreadsServicingQueue(0), stopRequested(false), stopWhenEmpty(false)
{
}
CScheduler::~CScheduler()
{
assert(nThreadsServicingQueue == 0);
}
#if BOOST_VERSION < 105000
static boost::system_time toPosixTime(const boost::chrono::system_clock::time_point& t)
{
// Creating the posix_time using from_time_t loses sub-second precision. So rather than exporting the time_point to time_t,
// start with a posix_time at the epoch (0) and add the milliseconds that have passed since then.
return boost::posix_time::from_time_t(0) + boost::posix_time::milliseconds(boost::chrono::duration_cast<boost::chrono::milliseconds>(t.time_since_epoch()).count());
}
#endif
void CScheduler::serviceQueue()
{
boost::unique_lock<boost::mutex> lock(newTaskMutex);
++nThreadsServicingQueue;
// newTaskMutex is locked throughout this loop EXCEPT
// when the thread is waiting or when the user's function
// is called.
while (!shouldStop()) {
try {
if (!shouldStop() && taskQueue.empty()) {
reverse_lock<boost::unique_lock<boost::mutex> > rlock(lock);
// Use this chance to get a tiny bit more entropy
RandAddSeedSleep();
}
while (!shouldStop() && taskQueue.empty()) {
// Wait until there is something to do.
newTaskScheduled.wait(lock);
}
// Wait until either there is a new task, or until
// the time of the first item on the queue:
// wait_until needs boost 1.50 or later; older versions have timed_wait:
#if BOOST_VERSION < 105000
while (!shouldStop() && !taskQueue.empty() &&
newTaskScheduled.timed_wait(lock, toPosixTime(taskQueue.begin()->first))) {
// Keep waiting until timeout
}
#else
// Some boost versions have a conflicting overload of wait_until that returns void.
// Explicitly use a template here to avoid hitting that overload.
while (!shouldStop() && !taskQueue.empty()) {
boost::chrono::system_clock::time_point timeToWaitFor = taskQueue.begin()->first;
if (newTaskScheduled.wait_until<>(lock, timeToWaitFor) == boost::cv_status::timeout)
break; // Exit loop after timeout, it means we reached the time of the event
}
#endif
// If there are multiple threads, the queue can empty while we're waiting (another
// thread may service the task we were waiting on).
if (shouldStop() || taskQueue.empty())
continue;
Function f = taskQueue.begin()->second;
taskQueue.erase(taskQueue.begin());
{
// Unlock before calling f, so it can reschedule itself or another task
// without deadlocking:
reverse_lock<boost::unique_lock<boost::mutex> > rlock(lock);
f();
}
} catch (...) {
--nThreadsServicingQueue;
throw;
}
}
--nThreadsServicingQueue;
newTaskScheduled.notify_one();
}
void CScheduler::stop(bool drain)
{
{
boost::unique_lock<boost::mutex> lock(newTaskMutex);
if (drain)
stopWhenEmpty = true;
else
stopRequested = true;
}
newTaskScheduled.notify_all();
}
void CScheduler::schedule(CScheduler::Function f, boost::chrono::system_clock::time_point t)
{
{
boost::unique_lock<boost::mutex> lock(newTaskMutex);
taskQueue.insert(std::make_pair(t, f));
}
newTaskScheduled.notify_one();
}
void CScheduler::scheduleFromNow(CScheduler::Function f, int64_t deltaMilliSeconds)
{
schedule(f, boost::chrono::system_clock::now() + boost::chrono::milliseconds(deltaMilliSeconds));
}
static void Repeat(CScheduler* s, CScheduler::Function f, int64_t deltaMilliSeconds)
{
f();
s->scheduleFromNow(boost::bind(&Repeat, s, f, deltaMilliSeconds), deltaMilliSeconds);
}
void CScheduler::scheduleEvery(CScheduler::Function f, int64_t deltaMilliSeconds)
{
scheduleFromNow(boost::bind(&Repeat, this, f, deltaMilliSeconds), deltaMilliSeconds);
}
size_t CScheduler::getQueueInfo(boost::chrono::system_clock::time_point &first,
boost::chrono::system_clock::time_point &last) const
{
boost::unique_lock<boost::mutex> lock(newTaskMutex);
size_t result = taskQueue.size();
if (!taskQueue.empty()) {
first = taskQueue.begin()->first;
last = taskQueue.rbegin()->first;
}
return result;
}
bool CScheduler::AreThreadsServicingQueue() const {
boost::unique_lock<boost::mutex> lock(newTaskMutex);
return nThreadsServicingQueue;
}
void SingleThreadedSchedulerClient::MaybeScheduleProcessQueue() {
{
LOCK(m_cs_callbacks_pending);
// Try to avoid scheduling too many copies here, but if we
// accidentally have two ProcessQueue's scheduled at once its
// not a big deal.
if (m_are_callbacks_running) return;
if (m_callbacks_pending.empty()) return;
}
m_pscheduler->schedule(std::bind(&SingleThreadedSchedulerClient::ProcessQueue, this));
}
void SingleThreadedSchedulerClient::ProcessQueue() {
std::function<void (void)> callback;
{
LOCK(m_cs_callbacks_pending);
if (m_are_callbacks_running) return;
if (m_callbacks_pending.empty()) return;
m_are_callbacks_running = true;
callback = std::move(m_callbacks_pending.front());
m_callbacks_pending.pop_front();
}
// RAII the setting of fCallbacksRunning and calling MaybeScheduleProcessQueue
// to ensure both happen safely even if callback() throws.
struct RAIICallbacksRunning {
SingleThreadedSchedulerClient* instance;
explicit RAIICallbacksRunning(SingleThreadedSchedulerClient* _instance) : instance(_instance) {}
~RAIICallbacksRunning() {
{
LOCK(instance->m_cs_callbacks_pending);
instance->m_are_callbacks_running = false;
}
instance->MaybeScheduleProcessQueue();
}
} raiicallbacksrunning(this);
callback();
}
void SingleThreadedSchedulerClient::AddToProcessQueue(std::function<void (void)> func) {
assert(m_pscheduler);
{
LOCK(m_cs_callbacks_pending);
m_callbacks_pending.emplace_back(std::move(func));
}
MaybeScheduleProcessQueue();
}
void SingleThreadedSchedulerClient::EmptyQueue() {
assert(!m_pscheduler->AreThreadsServicingQueue());
bool should_continue = true;
while (should_continue) {
ProcessQueue();
LOCK(m_cs_callbacks_pending);
should_continue = !m_callbacks_pending.empty();
}
}
size_t SingleThreadedSchedulerClient::CallbacksPending() {
LOCK(m_cs_callbacks_pending);
return m_callbacks_pending.size();
}