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
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
|
// Copyright (c) 2015-2016 The Bitcoin Core 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;
}
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;
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();
}
|
