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/*
* Copyright (C) 2006 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package dalvik.system;
import java.io.File;
/**
* Provides hooks for the zygote to call back into the runtime to perform
* parent or child specific initialization..
*
* @hide
*/
public final class ZygoteHooks {
private long token;
/**
* Called by the zygote prior to every fork. Each call to {@code preFork}
* is followed by a matching call to {@link #postForkChild(int)} on the child
* process and {@link #postForkCommon()} on both the parent and the child
* process. {@code postForkCommon} is called after {@code postForkChild} in
* the child process.
*/
public void preFork() {
Daemons.stop();
waitUntilAllThreadsStopped();
token = nativePreFork();
}
/**
* Called by the zygote in the child process after every fork. The debug
* flags from {@code debugFlags} are applied to the child process. The string
* {@code instructionSet} determines whether to use a native bridge.
*/
public void postForkChild(int debugFlags, String instructionSet) {
nativePostForkChild(token, debugFlags, instructionSet);
}
/**
* Called by the zygote in both the parent and child processes after
* every fork. In the child process, this method is called after
* {@code postForkChild}.
*/
public void postForkCommon() {
Daemons.start();
}
private static native long nativePreFork();
private static native void nativePostForkChild(long token, int debugFlags,
String instructionSet);
/**
* We must not fork until we're single-threaded again. Wait until /proc shows we're
* down to just one thread.
*/
private static void waitUntilAllThreadsStopped() {
File tasks = new File("/proc/self/task");
while (tasks.list().length > 1) {
try {
// Experimentally, booting and playing about with a stingray, I never saw us
// go round this loop more than once with a 10ms sleep.
Thread.sleep(10);
} catch (InterruptedException ignored) {
}
}
}
}
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