diff --git a/src/scheduler.h b/src/scheduler.h index f5fc25ec04..3b935014a4 100644 --- a/src/scheduler.h +++ b/src/scheduler.h @@ -1,133 +1,133 @@ // Copyright (c) 2015 The Bitcoin Core developers // Distributed under the MIT software license, see the accompanying // file COPYING or http://www.opensource.org/licenses/mit-license.php. #ifndef BITCOIN_SCHEDULER_H #define BITCOIN_SCHEDULER_H #include // // NOTE: // boost::thread / boost::chrono should be ported to // std::thread / std::chrono when we support C++11. // #include #include #include // // Simple class for background tasks that should be run periodically or once // "after a while" // // Usage: // // CScheduler* s = new CScheduler(); // s->scheduleFromNow(doSomething, 11); // Assuming a: void doSomething() { } // s->scheduleFromNow(std::bind(Class::func, this, argument), 3); // boost::thread* t = new boost::thread(std::bind(CScheduler::serviceQueue, s)); // // ... then at program shutdown, clean up the thread running serviceQueue: // t->interrupt(); // t->join(); // delete t; // delete s; // Must be done after thread is interrupted/joined. // class CScheduler { public: CScheduler(); ~CScheduler(); typedef std::function Function; typedef std::function Predicate; // Call func at/after time t void schedule(Function f, boost::chrono::system_clock::time_point t = boost::chrono::system_clock::now()); // Convenience method: call f once deltaMilliSeconds from now void scheduleFromNow(Function f, int64_t deltaMilliSeconds); // Another convenience method: call p approximately every deltaMilliSeconds // forever, starting deltaMilliSeconds from now untill p returns false. To // be more precise: every time p is finished, it is rescheduled to run // deltaMilliSeconds later. If you need more accurate scheduling, don't use // this method. void scheduleEvery(Predicate p, int64_t deltaMilliSeconds); // To keep things as simple as possible, there is no unschedule. // Services the queue 'forever'. Should be run in a thread, and interrupted // using boost::interrupt_thread void serviceQueue(); // Tell any threads running serviceQueue to stop as soon as they're done // servicing whatever task they're currently servicing (drain=false) or when // there is no work left to be done (drain=true) void stop(bool drain = false); // Returns number of tasks waiting to be serviced, and first and last task // times size_t getQueueInfo(boost::chrono::system_clock::time_point &first, boost::chrono::system_clock::time_point &last) const; // Returns true if there are threads actively running in serviceQueue() bool AreThreadsServicingQueue() const; private: std::multimap taskQueue; boost::condition_variable newTaskScheduled; mutable boost::mutex newTaskMutex; int nThreadsServicingQueue; bool stopRequested; bool stopWhenEmpty; bool shouldStop() const { return stopRequested || (stopWhenEmpty && taskQueue.empty()); } }; /** * Class used by CScheduler clients which may schedule multiple jobs * which are required to be run serially. Jobs may not be run on the * same thread, but no two jobs will be executed * at the same time and memory will be release-acquire consistent * (the scheduler will internally do an acquire before invoking a callback * as well as a release at the end). In practice this means that a callback * B() will be able to observe all of the effects of callback A() which executed * before it. */ class SingleThreadedSchedulerClient { private: CScheduler *m_pscheduler; CCriticalSection m_cs_callbacks_pending; std::list> m_callbacks_pending GUARDED_BY(m_cs_callbacks_pending); bool m_are_callbacks_running GUARDED_BY(m_cs_callbacks_pending) = false; void MaybeScheduleProcessQueue(); void ProcessQueue(); public: explicit SingleThreadedSchedulerClient(CScheduler *pschedulerIn) : m_pscheduler(pschedulerIn) {} /** * Add a callback to be executed. Callbacks are executed serially - * and memory is sequentially consistent between callback executions. + * and memory is release-acquire consistent between callback executions. * Practially, this means that callbacks can behave as if they are executed * in order by a single thread. */ void AddToProcessQueue(std::function func); // Processes all remaining queue members on the calling thread, blocking // until queue is empty. Must be called after the CScheduler has no // remaining processing threads! void EmptyQueue(); size_t CallbacksPending(); }; #endif