1 /*
2  * Copyright (C) 2013 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 package com.android.internal.os;
18 
19 import android.os.Handler;
20 import android.os.HandlerExecutor;
21 import android.os.HandlerThread;
22 import android.os.Looper;
23 import android.os.Trace;
24 
25 import java.util.concurrent.Executor;
26 
27 /**
28  * Shared singleton background thread for each process.
29  */
30 public final class BackgroundThread extends HandlerThread {
31     private static final long SLOW_DISPATCH_THRESHOLD_MS = 10_000;
32     private static final long SLOW_DELIVERY_THRESHOLD_MS = 30_000;
33     private static BackgroundThread sInstance;
34     private static Handler sHandler;
35     private static HandlerExecutor sHandlerExecutor;
36 
BackgroundThread()37     private BackgroundThread() {
38         super("android.bg", android.os.Process.THREAD_PRIORITY_BACKGROUND);
39     }
40 
ensureThreadLocked()41     private static void ensureThreadLocked() {
42         if (sInstance == null) {
43             sInstance = new BackgroundThread();
44             sInstance.start();
45             final Looper looper = sInstance.getLooper();
46             looper.setTraceTag(Trace.TRACE_TAG_SYSTEM_SERVER);
47             looper.setSlowLogThresholdMs(
48                     SLOW_DISPATCH_THRESHOLD_MS, SLOW_DELIVERY_THRESHOLD_MS);
49             sHandler = new Handler(sInstance.getLooper());
50             sHandlerExecutor = new HandlerExecutor(sHandler);
51         }
52     }
53 
get()54     public static BackgroundThread get() {
55         synchronized (BackgroundThread.class) {
56             ensureThreadLocked();
57             return sInstance;
58         }
59     }
60 
getHandler()61     public static Handler getHandler() {
62         synchronized (BackgroundThread.class) {
63             ensureThreadLocked();
64             return sHandler;
65         }
66     }
67 
getExecutor()68     public static Executor getExecutor() {
69         synchronized (BackgroundThread.class) {
70             ensureThreadLocked();
71             return sHandlerExecutor;
72         }
73     }
74 }
75