1 /**
2 * Copyright (C) 2021 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include "EvsCallbackThread.h"
18
19 #include <android-base/logging.h>
20
21 namespace android {
22 namespace automotive {
23 namespace evs {
24
EvsCallbackThread(JavaVM * vm)25 EvsCallbackThread::EvsCallbackThread(JavaVM* vm) :
26 mVm(vm), mRunning(true), mThread(&EvsCallbackThread::threadLoop, this) {
27 LOG(DEBUG) << "Started the native callback handler thread = " << this;
28 }
29
~EvsCallbackThread()30 EvsCallbackThread::~EvsCallbackThread() {
31 // Stops the loop
32 stop();
33 }
34
threadLoop()35 void EvsCallbackThread::threadLoop() {
36 // Attaches the current thread to the Java VM.
37 JNIEnv* env = nullptr;
38 JavaVMAttachArgs args = {JNI_VERSION_1_4, "EvsCallbackThread", nullptr};
39 if (mVm->AttachCurrentThread(&env, &args) != JNI_OK || env == nullptr) {
40 LOG(ERROR) << "Failed to be attached to the VM.";
41 mRunning = false;
42 return;
43 }
44
45 while (true) {
46 Task task;
47 {
48 std::unique_lock<std::mutex> lock(mLock);
49 if (!mRunning) {
50 break;
51 }
52
53 if (mTaskQueue.empty()) {
54 mCondition.wait(lock);
55 // The conditional variable is signalled when either a new task
56 // is enqueued or we are requested to stop. If we wake up
57 // spuriously, the task queue must be empty so go back to sleep.
58 if (!mRunning) {
59 break;
60 } else if (mTaskQueue.empty()) {
61 LOG(DEBUG) << "No pending tasks; continue.";
62 continue;
63 }
64 }
65
66 task = mTaskQueue.front();
67 mTaskQueue.pop();
68 }
69
70 // Executes the task and check the exception
71 task(env);
72 if (env->ExceptionCheck()) {
73 LOG(ERROR) << "Exception happens while handling a task:";
74 env->ExceptionDescribe();
75 env->ExceptionClear();
76 }
77 }
78
79 auto res = mVm->DetachCurrentThread();
80 if (res != JNI_OK) {
81 LOG(WARNING) << "Failed to be detached from the VM.";
82 }
83
84 if (!mTaskQueue.empty()) {
85 LOG(WARNING) << mTaskQueue.size() << " tasks are ignored.";
86 }
87
88 LOG(DEBUG) << "Exiting a callback handler thread.";
89 }
90
enqueue(const Task & task)91 void EvsCallbackThread::enqueue(const Task& task) {
92 std::lock_guard<std::mutex> lock(mLock);
93 if (!mRunning) {
94 LOG(WARNING) << "A callback handler thread is not running.";
95 return;
96 }
97
98 mTaskQueue.push(task);
99 mCondition.notify_one();
100 }
101
stop()102 void EvsCallbackThread::stop() {
103 {
104 std::lock_guard<std::mutex> lock(mLock);
105 if (!mRunning) {
106 // Nothing to do if the handler thread is not running.
107 return;
108 }
109
110 mRunning = false;
111 mCondition.notify_all();
112 }
113
114 if (mThread.get_id() == std::this_thread::get_id()) {
115 // Should not join by myself
116 mThread.detach();
117 } else if (mThread.joinable()) {
118 mThread.join();
119 }
120 }
121
122 } // namespace evs
123 } // namespace automotive
124 } // namespace android
125