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 17 package dalvik.system; 18 19 import java.io.File; 20 21 /** 22 * Provides hooks for the zygote to call back into the runtime to perform 23 * parent or child specific initialization.. 24 * 25 * @hide 26 */ 27 public final class ZygoteHooks { 28 private long token; 29 30 /** 31 * Called by the zygote prior to every fork. Each call to {@code preFork} 32 * is followed by a matching call to {@link #postForkChild(int, String)} on the child 33 * process and {@link #postForkCommon()} on both the parent and the child 34 * process. {@code postForkCommon} is called after {@code postForkChild} in 35 * the child process. 36 */ 37 public void preFork() { 38 Daemons.stop(); 39 waitUntilAllThreadsStopped(); 40 token = nativePreFork(); 41 } 42 43 /** 44 * Called by the zygote in the child process after every fork. The debug 45 * flags from {@code debugFlags} are applied to the child process. The string 46 * {@code instructionSet} determines whether to use a native bridge. 47 */ 48 public void postForkChild(int debugFlags, String instructionSet) { 49 nativePostForkChild(token, debugFlags, instructionSet); 50 51 Math.setRandomSeedInternal(System.currentTimeMillis()); 52 } 53 54 /** 55 * Called by the zygote in both the parent and child processes after 56 * every fork. In the child process, this method is called after 57 * {@code postForkChild}. 58 */ 59 public void postForkCommon() { 60 Daemons.start(); 61 } 62 63 private static native long nativePreFork(); 64 private static native void nativePostForkChild(long token, int debugFlags, 65 String instructionSet); 66 67 /** 68 * We must not fork until we're single-threaded again. Wait until /proc shows we're 69 * down to just one thread. 70 */ 71 private static void waitUntilAllThreadsStopped() { 72 File tasks = new File("/proc/self/task"); 73 // All Java daemons are stopped already. We're just waiting for their OS counterparts to 74 // finish as well. This shouldn't take much time so spinning is ok here. 75 while (tasks.list().length > 1) { 76 Thread.yield(); 77 } 78 } 79 } 80