SystemService.java revision 6090995951c6e2e4dcf38102f01793f8a94166e1 
1/*
2 * Copyright (C) 2006 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
17package android.os;
18
19import com.google.android.collect.Maps;
20
21import java.util.HashMap;
22import java.util.concurrent.TimeoutException;
23
24/**
25 * Controls and utilities for low-level {@code init} services.
26 *
27 * @hide
28 */
29public class SystemService {
30
31    private static HashMap<String, State> sStates = Maps.newHashMap();
32
33    /**
34     * State of a known {@code init} service.
35     */
36    public enum State {
37        RUNNING("running"),
38        STOPPING("stopping"),
39        STOPPED("stopped"),
40        RESTARTING("restarting");
41
42        State(String state) {
43            sStates.put(state, this);
44        }
45    }
46
47    private static Object sPropertyLock = new Object();
48
49    static {
50        SystemProperties.addChangeCallback(new Runnable() {
51            @Override
52            public void run() {
53                synchronized (sPropertyLock) {
54                    sPropertyLock.notifyAll();
55                }
56            }
57        });
58    }
59
60    /** Request that the init daemon start a named service. */
61    public static void start(String name) {
62        SystemProperties.set("ctl.start", name);
63    }
64
65    /** Request that the init daemon stop a named service. */
66    public static void stop(String name) {
67        SystemProperties.set("ctl.stop", name);
68    }
69
70    /** Request that the init daemon restart a named service. */
71    public static void restart(String name) {
72        SystemProperties.set("ctl.restart", name);
73    }
74
75    /**
76     * Return current state of given service.
77     */
78    public static State getState(String service) {
79        final String rawState = SystemProperties.get("init.svc." + service);
80        final State state = sStates.get(rawState);
81        if (state != null) {
82            return state;
83        } else {
84            return State.STOPPED;
85        }
86    }
87
88    /**
89     * Check if given service is {@link State#STOPPED}.
90     */
91    public static boolean isStopped(String service) {
92        return State.STOPPED.equals(getState(service));
93    }
94
95    /**
96     * Check if given service is {@link State#RUNNING}.
97     */
98    public static boolean isRunning(String service) {
99        return State.RUNNING.equals(getState(service));
100    }
101
102    /**
103     * Wait until given service has entered specific state.
104     */
105    public static void waitForState(String service, State state, long timeoutMillis)
106            throws TimeoutException {
107        final long endMillis = SystemClock.elapsedRealtime() + timeoutMillis;
108        while (true) {
109            synchronized (sPropertyLock) {
110                final State currentState = getState(service);
111                if (state.equals(currentState)) {
112                    return;
113                }
114
115                if (SystemClock.elapsedRealtime() >= endMillis) {
116                    throw new TimeoutException("Service " + service + " currently " + currentState
117                            + "; waited " + timeoutMillis + "ms for " + state);
118                }
119
120                try {
121                    sPropertyLock.wait(timeoutMillis);
122                } catch (InterruptedException e) {
123                }
124            }
125        }
126    }
127
128    /**
129     * Wait until any of given services enters {@link State#STOPPED}.
130     */
131    public static void waitForAnyStopped(String... services)  {
132        while (true) {
133            synchronized (sPropertyLock) {
134                for (String service : services) {
135                    if (State.STOPPED.equals(getState(service))) {
136                        return;
137                    }
138                }
139
140                try {
141                    sPropertyLock.wait();
142                } catch (InterruptedException e) {
143                }
144            }
145        }
146    }
147}
148