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(), /*callback=*/ null, /* async=*/ false,
50                     /* shared=*/ true);
51             sHandlerExecutor = new HandlerExecutor(sHandler);
52         }
53     }
54 
get()55     public static BackgroundThread get() {
56         synchronized (BackgroundThread.class) {
57             ensureThreadLocked();
58             return sInstance;
59         }
60     }
61 
getHandler()62     public static Handler getHandler() {
63         synchronized (BackgroundThread.class) {
64             ensureThreadLocked();
65             return sHandler;
66         }
67     }
68 
getExecutor()69     public static Executor getExecutor() {
70         synchronized (BackgroundThread.class) {
71             ensureThreadLocked();
72             return sHandlerExecutor;
73         }
74     }
75 }
76