1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
|
// Copyright (c) 2015-2020 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
//
// NOTE:
// boost::thread should be ported to std::thread
// when we support C++11.
//
#include <condition_variable>
#include <functional>
#include <list>
#include <map>
#include <sync.h>
//
// 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, make sure to call stop() to clean up the thread(s) running serviceQueue:
// s->stop();
// t->join();
// delete t;
// delete s; // Must be done after thread is interrupted/joined.
//
class CScheduler
{
public:
CScheduler();
~CScheduler();
typedef std::function<void()> Function;
// Call func at/after time t
void schedule(Function f, std::chrono::system_clock::time_point t);
// Convenience method: call f once deltaMilliSeconds from now
void scheduleFromNow(Function f, int64_t deltaMilliSeconds);
// Another convenience method: call f approximately
// every deltaMilliSeconds forever, starting deltaMilliSeconds from now.
// To be more precise: every time f is finished, it
// is rescheduled to run deltaMilliSeconds later. If you
// need more accurate scheduling, don't use this method.
void scheduleEvery(Function f, int64_t deltaMilliSeconds);
/**
* Mock the scheduler to fast forward in time.
* Iterates through items on taskQueue and reschedules them
* to be delta_seconds sooner.
*/
void MockForward(std::chrono::seconds delta_seconds);
// 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(std::chrono::system_clock::time_point &first,
std::chrono::system_clock::time_point &last) const;
// Returns true if there are threads actively running in serviceQueue()
bool AreThreadsServicingQueue() const;
private:
mutable Mutex newTaskMutex;
std::condition_variable newTaskScheduled;
std::multimap<std::chrono::system_clock::time_point, Function> taskQueue GUARDED_BY(newTaskMutex);
int nThreadsServicingQueue GUARDED_BY(newTaskMutex){0};
bool stopRequested GUARDED_BY(newTaskMutex){false};
bool stopWhenEmpty GUARDED_BY(newTaskMutex){false};
bool shouldStop() const EXCLUSIVE_LOCKS_REQUIRED(newTaskMutex) { 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;
RecursiveMutex m_cs_callbacks_pending;
std::list<std::function<void ()>> 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 release-acquire consistent between callback executions.
* Practically, this means that callbacks can behave as if they are executed
* in order by a single thread.
*/
void AddToProcessQueue(std::function<void ()> 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
|
