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127 lines
4.4 KiB
127 lines
4.4 KiB
// Copyright (c) 2015-2018 The Bitcoin Core developers
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// Distributed under the MIT software license, see the accompanying
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// file COPYING or http://www.opensource.org/licenses/mit-license.php.
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#ifndef BITCOIN_SCHEDULER_H
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#define BITCOIN_SCHEDULER_H
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//
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// NOTE:
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// boost::thread / boost::chrono should be ported to std::thread / std::chrono
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// when we support C++11.
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//
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#include <boost/chrono/chrono.hpp>
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#include <boost/thread.hpp>
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#include <map>
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#include <sync.h>
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//
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// Simple class for background tasks that should be run
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// periodically or once "after a while"
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//
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// Usage:
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//
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// CScheduler* s = new CScheduler();
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// s->scheduleFromNow(doSomething, 11); // Assuming a: void doSomething() { }
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// s->scheduleFromNow(std::bind(Class::func, this, argument), 3);
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// boost::thread* t = new boost::thread(std::bind(CScheduler::serviceQueue, s));
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//
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// ... then at program shutdown, clean up the thread running serviceQueue:
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// t->interrupt();
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// t->join();
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// delete t;
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// delete s; // Must be done after thread is interrupted/joined.
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//
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class CScheduler
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{
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public:
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CScheduler();
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~CScheduler();
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typedef std::function<void()> Function;
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// Call func at/after time t
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void schedule(Function f, boost::chrono::system_clock::time_point t=boost::chrono::system_clock::now());
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// Convenience method: call f once deltaMilliSeconds from now
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void scheduleFromNow(Function f, int64_t deltaMilliSeconds);
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// Another convenience method: call f approximately
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// every deltaMilliSeconds forever, starting deltaMilliSeconds from now.
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// To be more precise: every time f is finished, it
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// is rescheduled to run deltaMilliSeconds later. If you
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// need more accurate scheduling, don't use this method.
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void scheduleEvery(Function f, int64_t deltaMilliSeconds);
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// To keep things as simple as possible, there is no unschedule.
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// Services the queue 'forever'. Should be run in a thread,
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// and interrupted using boost::interrupt_thread
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void serviceQueue();
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// Tell any threads running serviceQueue to stop as soon as they're
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// done servicing whatever task they're currently servicing (drain=false)
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// or when there is no work left to be done (drain=true)
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void stop(bool drain=false);
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// Returns number of tasks waiting to be serviced,
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// and first and last task times
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size_t getQueueInfo(boost::chrono::system_clock::time_point &first,
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boost::chrono::system_clock::time_point &last) const;
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// Returns true if there are threads actively running in serviceQueue()
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bool AreThreadsServicingQueue() const;
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private:
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std::multimap<boost::chrono::system_clock::time_point, Function> taskQueue;
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boost::condition_variable newTaskScheduled;
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mutable boost::mutex newTaskMutex;
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int nThreadsServicingQueue;
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bool stopRequested;
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bool stopWhenEmpty;
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bool shouldStop() const { return stopRequested || (stopWhenEmpty && taskQueue.empty()); }
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};
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/**
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* Class used by CScheduler clients which may schedule multiple jobs
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* which are required to be run serially. Jobs may not be run on the
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* same thread, but no two jobs will be executed
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* at the same time and memory will be release-acquire consistent
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* (the scheduler will internally do an acquire before invoking a callback
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* as well as a release at the end). In practice this means that a callback
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* B() will be able to observe all of the effects of callback A() which executed
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* before it.
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*/
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class SingleThreadedSchedulerClient {
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private:
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CScheduler *m_pscheduler;
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CCriticalSection m_cs_callbacks_pending;
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std::list<std::function<void ()>> m_callbacks_pending GUARDED_BY(m_cs_callbacks_pending);
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bool m_are_callbacks_running GUARDED_BY(m_cs_callbacks_pending) = false;
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void MaybeScheduleProcessQueue();
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void ProcessQueue();
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public:
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explicit SingleThreadedSchedulerClient(CScheduler *pschedulerIn) : m_pscheduler(pschedulerIn) {}
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/**
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* Add a callback to be executed. Callbacks are executed serially
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* and memory is release-acquire consistent between callback executions.
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* Practically, this means that callbacks can behave as if they are executed
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* in order by a single thread.
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*/
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void AddToProcessQueue(std::function<void ()> func);
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// Processes all remaining queue members on the calling thread, blocking until queue is empty
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// Must be called after the CScheduler has no remaining processing threads!
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void EmptyQueue();
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size_t CallbacksPending();
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};
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#endif
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