1 // Copyright 2023 The Pigweed Authors
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License"); you may not
4 // use this file except in compliance with the License. You may obtain a copy of
5 // the License at
6 //
7 // https://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
11 // WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
12 // License for the specific language governing permissions and limitations under
13 // the License.
14 #include "pw_async_basic/dispatcher.h"
15
16 #include <mutex>
17
18 #include "pw_chrono/system_clock.h"
19
20 using namespace std::chrono_literals;
21
22 namespace pw::async {
23
~BasicDispatcher()24 BasicDispatcher::~BasicDispatcher() {
25 RequestStop();
26 lock_.lock();
27 DrainTaskQueue();
28 lock_.unlock();
29 }
30
Run()31 void BasicDispatcher::Run() {
32 lock_.lock();
33 while (!stop_requested_) {
34 MaybeSleep();
35 ExecuteDueTasks();
36 }
37 DrainTaskQueue();
38 lock_.unlock();
39 }
40
RunUntilIdle()41 void BasicDispatcher::RunUntilIdle() {
42 lock_.lock();
43 ExecuteDueTasks();
44 if (stop_requested_) {
45 DrainTaskQueue();
46 }
47 lock_.unlock();
48 }
49
RunUntil(chrono::SystemClock::time_point end_time)50 void BasicDispatcher::RunUntil(chrono::SystemClock::time_point end_time) {
51 lock_.lock();
52 while (end_time < now() && !stop_requested_) {
53 MaybeSleep();
54 ExecuteDueTasks();
55 }
56 if (stop_requested_) {
57 DrainTaskQueue();
58 }
59 lock_.unlock();
60 }
61
RunFor(chrono::SystemClock::duration duration)62 void BasicDispatcher::RunFor(chrono::SystemClock::duration duration) {
63 RunUntil(now() + duration);
64 }
65
MaybeSleep()66 void BasicDispatcher::MaybeSleep() {
67 if (task_queue_.empty() || task_queue_.front().due_time_ > now()) {
68 // Sleep until a notification is received or until the due time of the
69 // next task. Notifications are sent when tasks are posted or 'stop' is
70 // requested.
71 std::optional<chrono::SystemClock::time_point> wake_time = std::nullopt;
72 if (!task_queue_.empty()) {
73 wake_time = task_queue_.front().due_time_;
74 }
75 lock_.unlock();
76 if (wake_time.has_value()) {
77 timed_notification_.try_acquire_until(*wake_time);
78 } else {
79 timed_notification_.acquire();
80 }
81 lock_.lock();
82 }
83 }
84
ExecuteDueTasks()85 void BasicDispatcher::ExecuteDueTasks() {
86 while (!task_queue_.empty() && task_queue_.front().due_time_ <= now() &&
87 !stop_requested_) {
88 backend::NativeTask& task = task_queue_.front();
89 task_queue_.pop_front();
90
91 lock_.unlock();
92 Context ctx{this, &task.task_};
93 task(ctx, OkStatus());
94 lock_.lock();
95 }
96 }
97
RequestStop()98 void BasicDispatcher::RequestStop() {
99 {
100 std::lock_guard lock(lock_);
101 stop_requested_ = true;
102 }
103 timed_notification_.release();
104 }
105
DrainTaskQueue()106 void BasicDispatcher::DrainTaskQueue() {
107 while (!task_queue_.empty()) {
108 backend::NativeTask& task = task_queue_.front();
109 task_queue_.pop_front();
110
111 lock_.unlock();
112 Context ctx{this, &task.task_};
113 task(ctx, Status::Cancelled());
114 lock_.lock();
115 }
116 }
117
PostAt(Task & task,chrono::SystemClock::time_point time)118 void BasicDispatcher::PostAt(Task& task, chrono::SystemClock::time_point time) {
119 PostTaskInternal(task.native_type(), time);
120 }
121
Cancel(Task & task)122 bool BasicDispatcher::Cancel(Task& task) {
123 std::lock_guard lock(lock_);
124 return task_queue_.remove(task.native_type());
125 }
126
PostTaskInternal(backend::NativeTask & task,chrono::SystemClock::time_point time_due)127 void BasicDispatcher::PostTaskInternal(
128 backend::NativeTask& task, chrono::SystemClock::time_point time_due) {
129 lock_.lock();
130 task.due_time_ = time_due;
131 // Insert the new task in the queue after all tasks with the same or earlier
132 // deadline to ensure FIFO execution order.
133 auto it_front = task_queue_.begin();
134 auto it_behind = task_queue_.before_begin();
135 while (it_front != task_queue_.end() && time_due >= it_front->due_time_) {
136 ++it_front;
137 ++it_behind;
138 }
139 task_queue_.insert_after(it_behind, task);
140 lock_.unlock();
141 timed_notification_.release();
142 }
143
144 } // namespace pw::async
145