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
|
#pragma once
#include <mbgl/actor/actor.hpp>
#include <mbgl/actor/mailbox.hpp>
#include <mbgl/actor/scheduler.hpp>
#include <mbgl/util/platform.hpp>
#include <mbgl/util/run_loop.hpp>
#include <mbgl/util/util.hpp>
#include <cassert>
#include <future>
#include <memory>
#include <mutex>
#include <queue>
#include <string>
#include <thread>
#include <utility>
namespace mbgl {
namespace util {
// Manages a thread with `Object`.
// Upon creation of this object, it launches a thread and creates an object of type `Object`
// in that thread. When the `Thread<>` object is destructed, the destructor waits
// for thread termination. The `Thread<>` constructor blocks until the thread and
// the `Object` are fully created, so after the object creation, it's safe to obtain the
// `Object` stored in this thread. The thread created will always have low priority on
// the platforms that support setting thread priority.
//
// The following properties make this class different from `ThreadPool`:
//
// - Only one thread is created.
// - `Object` will live in a single thread, providing thread affinity.
// - It is safe to use `ThreadLocal` in an `Object` managed by `Thread<>`
// - A `RunLoop` is created for the `Object` thread.
// - `Object` can use `Timer` and do asynchronous I/O, like wait for sockets events.
//
template<class Object>
class Thread {
public:
template <class... Args>
Thread(const std::string& name, Args&&... args) {
std::promise<void> running_;
running = running_.get_future();
auto capturedArgs = std::make_tuple(std::forward<Args>(args)...);
thread = std::thread([
this,
name,
capturedArgs = std::move(capturedArgs),
runningPromise = std::move(running_)
] () mutable {
platform::setCurrentThreadName(name);
platform::makeThreadLowPriority();
util::RunLoop loop_(util::RunLoop::Type::New);
loop = &loop_;
EstablishedActor<Object> establishedActor(loop_, object, std::move(capturedArgs));
runningPromise.set_value();
loop->run();
(void) establishedActor;
loop = nullptr;
});
}
~Thread() {
if (paused) {
resume();
}
std::promise<void> stoppable;
running.wait();
// Invoke a noop task on the run loop to ensure that we're executing
// run() before we call stop()
loop->invoke([&] {
stoppable.set_value();
});
stoppable.get_future().get();
loop->stop();
thread.join();
}
// Returns a non-owning reference to `Object` that
// can be used to send messages to `Object`. It is safe
// to the non-owning reference to outlive this object
// and be used after the `Thread<>` gets destroyed.
ActorRef<std::decay_t<Object>> actor() {
return object.self();
}
// Pauses the `Object` thread. It will prevent the object to wake
// up from events such as timers and file descriptor I/O. Messages
// sent to a paused `Object` will be queued and only processed after
// `resume()` is called.
void pause() {
MBGL_VERIFY_THREAD(tid);
assert(!paused);
paused = std::make_unique<std::promise<void>>();
resumed = std::make_unique<std::promise<void>>();
auto pausing = paused->get_future();
running.wait();
loop->invoke(RunLoop::Priority::High, [this] {
auto resuming = resumed->get_future();
paused->set_value();
resuming.get();
});
pausing.get();
}
// Resumes the `Object` thread previously paused by `pause()`.
void resume() {
MBGL_VERIFY_THREAD(tid);
assert(paused);
resumed->set_value();
resumed.reset();
paused.reset();
}
private:
MBGL_STORE_THREAD(tid);
AspiringActor<Object> object;
std::thread thread;
std::future<void> running;
std::unique_ptr<std::promise<void>> paused;
std::unique_ptr<std::promise<void>> resumed;
util::RunLoop* loop = nullptr;
};
} // namespace util
} // namespace mbgl
|
