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
194
195
196
197
198
199
200
201
202
203
204
205
206
207
|
// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/files/file_descriptor_watcher_posix.h"
#include "base/bind.h"
#include "base/lazy_instance.h"
#include "base/logging.h"
#include "base/memory/ptr_util.h"
#include "base/sequenced_task_runner.h"
#include "base/single_thread_task_runner.h"
#include "base/threading/sequenced_task_runner_handle.h"
#include "base/threading/thread_checker.h"
#include "base/threading/thread_local.h"
namespace base {
namespace {
// MessageLoopForIO used to watch file descriptors for which callbacks are
// registered from a given thread.
LazyInstance<ThreadLocalPointer<MessageLoopForIO>>::Leaky
tls_message_loop_for_io = LAZY_INSTANCE_INITIALIZER;
} // namespace
FileDescriptorWatcher::Controller::~Controller() {
DCHECK(sequence_checker_.CalledOnValidSequence());
// Delete |watcher_| on the MessageLoopForIO.
//
// If the MessageLoopForIO is deleted before Watcher::StartWatching() runs,
// |watcher_| is leaked. If the MessageLoopForIO is deleted after
// Watcher::StartWatching() runs but before the DeleteSoon task runs,
// |watcher_| is deleted from Watcher::WillDestroyCurrentMessageLoop().
message_loop_for_io_task_runner_->DeleteSoon(FROM_HERE, watcher_.release());
// Since WeakPtrs are invalidated by the destructor, RunCallback() won't be
// invoked after this returns.
}
class FileDescriptorWatcher::Controller::Watcher
: public MessageLoopForIO::Watcher,
public MessageLoop::DestructionObserver {
public:
Watcher(WeakPtr<Controller> controller, MessageLoopForIO::Mode mode, int fd);
~Watcher() override;
void StartWatching();
private:
friend class FileDescriptorWatcher;
// MessageLoopForIO::Watcher:
void OnFileCanReadWithoutBlocking(int fd) override;
void OnFileCanWriteWithoutBlocking(int fd) override;
// MessageLoop::DestructionObserver:
void WillDestroyCurrentMessageLoop() override;
// Used to instruct the MessageLoopForIO to stop watching the file descriptor.
MessageLoopForIO::FileDescriptorWatcher file_descriptor_watcher_;
// Runs tasks on the sequence on which this was instantiated (i.e. the
// sequence on which the callback must run).
const scoped_refptr<SequencedTaskRunner> callback_task_runner_ =
SequencedTaskRunnerHandle::Get();
// The Controller that created this Watcher.
WeakPtr<Controller> controller_;
// Whether this Watcher is notified when |fd_| becomes readable or writable
// without blocking.
const MessageLoopForIO::Mode mode_;
// The watched file descriptor.
const int fd_;
// Except for the constructor, every method of this class must run on the same
// MessageLoopForIO thread.
ThreadChecker thread_checker_;
// Whether this Watcher was registered as a DestructionObserver on the
// MessageLoopForIO thread.
bool registered_as_destruction_observer_ = false;
DISALLOW_COPY_AND_ASSIGN(Watcher);
};
FileDescriptorWatcher::Controller::Watcher::Watcher(
WeakPtr<Controller> controller,
MessageLoopForIO::Mode mode,
int fd)
: controller_(controller), mode_(mode), fd_(fd) {
DCHECK(callback_task_runner_);
thread_checker_.DetachFromThread();
}
FileDescriptorWatcher::Controller::Watcher::~Watcher() {
DCHECK(thread_checker_.CalledOnValidThread());
MessageLoopForIO::current()->RemoveDestructionObserver(this);
}
void FileDescriptorWatcher::Controller::Watcher::StartWatching() {
DCHECK(thread_checker_.CalledOnValidThread());
MessageLoopForIO::current()->WatchFileDescriptor(
fd_, false, mode_, &file_descriptor_watcher_, this);
if (!registered_as_destruction_observer_) {
MessageLoopForIO::current()->AddDestructionObserver(this);
registered_as_destruction_observer_ = true;
}
}
void FileDescriptorWatcher::Controller::Watcher::OnFileCanReadWithoutBlocking(
int fd) {
DCHECK_EQ(fd_, fd);
DCHECK_EQ(MessageLoopForIO::WATCH_READ, mode_);
DCHECK(thread_checker_.CalledOnValidThread());
// Run the callback on the sequence on which the watch was initiated.
callback_task_runner_->PostTask(FROM_HERE,
Bind(&Controller::RunCallback, controller_));
}
void FileDescriptorWatcher::Controller::Watcher::OnFileCanWriteWithoutBlocking(
int fd) {
DCHECK_EQ(fd_, fd);
DCHECK_EQ(MessageLoopForIO::WATCH_WRITE, mode_);
DCHECK(thread_checker_.CalledOnValidThread());
// Run the callback on the sequence on which the watch was initiated.
callback_task_runner_->PostTask(FROM_HERE,
Bind(&Controller::RunCallback, controller_));
}
void FileDescriptorWatcher::Controller::Watcher::
WillDestroyCurrentMessageLoop() {
DCHECK(thread_checker_.CalledOnValidThread());
// A Watcher is owned by a Controller. When the Controller is deleted, it
// transfers ownership of the Watcher to a delete task posted to the
// MessageLoopForIO. If the MessageLoopForIO is deleted before the delete task
// runs, the following line takes care of deleting the Watcher.
delete this;
}
FileDescriptorWatcher::Controller::Controller(MessageLoopForIO::Mode mode,
int fd,
const Closure& callback)
: callback_(callback),
message_loop_for_io_task_runner_(
tls_message_loop_for_io.Get().Get()->task_runner()),
weak_factory_(this) {
DCHECK(!callback_.is_null());
DCHECK(message_loop_for_io_task_runner_);
watcher_ = MakeUnique<Watcher>(weak_factory_.GetWeakPtr(), mode, fd);
StartWatching();
}
void FileDescriptorWatcher::Controller::StartWatching() {
DCHECK(sequence_checker_.CalledOnValidSequence());
// It is safe to use Unretained() below because |watcher_| can only be deleted
// by a delete task posted to |message_loop_for_io_task_runner_| by this
// Controller's destructor. Since this delete task hasn't been posted yet, it
// can't run before the task posted below.
message_loop_for_io_task_runner_->PostTask(
FROM_HERE, Bind(&Watcher::StartWatching, Unretained(watcher_.get())));
}
void FileDescriptorWatcher::Controller::RunCallback() {
DCHECK(sequence_checker_.CalledOnValidSequence());
WeakPtr<Controller> weak_this = weak_factory_.GetWeakPtr();
callback_.Run();
// If |this| wasn't deleted, re-enable the watch.
if (weak_this)
StartWatching();
}
FileDescriptorWatcher::FileDescriptorWatcher(
MessageLoopForIO* message_loop_for_io) {
DCHECK(message_loop_for_io);
DCHECK(!tls_message_loop_for_io.Get().Get());
tls_message_loop_for_io.Get().Set(message_loop_for_io);
}
FileDescriptorWatcher::~FileDescriptorWatcher() {
tls_message_loop_for_io.Get().Set(nullptr);
}
std::unique_ptr<FileDescriptorWatcher::Controller>
FileDescriptorWatcher::WatchReadable(int fd, const Closure& callback) {
return WrapUnique(new Controller(MessageLoopForIO::WATCH_READ, fd, callback));
}
std::unique_ptr<FileDescriptorWatcher::Controller>
FileDescriptorWatcher::WatchWritable(int fd, const Closure& callback) {
return WrapUnique(
new Controller(MessageLoopForIO::WATCH_WRITE, fd, callback));
}
} // namespace base
|
