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
|
// Copyright 2020 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_TASK_BIND_POST_TASK_INTERNAL_H_
#define BASE_TASK_BIND_POST_TASK_INTERNAL_H_
#include <utility>
#include "base/check.h"
#include "base/functional/bind.h"
#include "base/functional/callback.h"
#include "base/location.h"
#include "base/task/task_runner.h"
#include "base/task/thread_pool/thread_pool_instance.h"
namespace base {
namespace internal {
// Helper class to ensure that the input callback is always invoked and
// destroyed on the provided task runner.
template <typename CallbackType>
class BindPostTaskTrampoline {
public:
BindPostTaskTrampoline(scoped_refptr<TaskRunner> task_runner,
const Location& location,
CallbackType callback)
: task_runner_(std::move(task_runner)),
location_(location),
callback_(std::move(callback)) {
DCHECK(task_runner_);
// Crash immediately instead of when trying to Run() `callback_` on the
// destination `task_runner_`.
CHECK(callback_);
}
BindPostTaskTrampoline(const BindPostTaskTrampoline& other) = delete;
BindPostTaskTrampoline& operator=(const BindPostTaskTrampoline& other) =
delete;
~BindPostTaskTrampoline() {
if (callback_) {
// Allow this task to be leaked on shutdown even if `task_runner_` has the
// TaskShutdownBehaviour::BLOCK_SHUTDOWN trait. Without `fizzler`, such a
// task runner would DCHECK when posting to `task_runner_` after shutdown.
// Ignore this DCHECK as the poster isn't in control when its Callback is
// destroyed late into shutdown. Ref. crbug.com/1375270.
base::ThreadPoolInstance::ScopedFizzleBlockShutdownTasks fizzler;
// Post a task to ensure that `callback_` is destroyed on `task_runner_`.
// The callback's BindState may own an object that isn't threadsafe and is
// unsafe to destroy on a different task runner.
//
// Note that while this guarantees `callback_` will be destroyed when the
// posted task runs, it doesn't guarantee the ref-counted BindState is
// destroyed at the same time. If the callback was copied before being
// passed to BindPostTaskTrampoline then the BindState can outlive
// `callback_`, so the user must ensure any other copies of the callback
// are also destroyed on the correct task runner.
task_runner_->PostTask(
location_,
base::BindOnce(&DestroyCallbackOnTaskRunner, std::move(callback_)));
}
}
template <typename... Args>
void Run(Args... args) {
// If CallbackType is a OnceCallback then GetClosure() consumes `callback_`.
task_runner_->PostTask(location_,
GetClosure(&callback_, std::forward<Args>(args)...));
}
private:
static OnceClosure GetClosure(OnceClosure* callback) {
// `callback` is already a closure, no need to call BindOnce().
return std::move(*callback);
}
template <typename... Args>
static OnceClosure GetClosure(OnceCallback<void(Args...)>* callback,
Args&&... args) {
return base::BindOnce(std::move(*callback), std::forward<Args>(args)...);
}
static OnceClosure GetClosure(RepeatingClosure* callback) {
// `callback` is already a closure, no need to call BindOnce().
return *callback;
}
template <typename... Args>
static OnceClosure GetClosure(RepeatingCallback<void(Args...)>* callback,
Args&&... args) {
return base::BindOnce(*callback, std::forward<Args>(args)...);
}
static void DestroyCallbackOnTaskRunner(CallbackType callback) {}
const scoped_refptr<TaskRunner> task_runner_;
const Location location_;
CallbackType callback_;
};
} // namespace internal
} // namespace base
#endif // BASE_TASK_BIND_POST_TASK_INTERNAL_H_
|
