应用进程异常被kill后ams重新拉起机制分析

最新推荐文章于 2024-07-31 09:53:33 发布

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最新推荐文章于 2024-07-31 09:53:33 发布 · 1.4k 阅读

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#android ams

当Android应用进程因异常被kill后，AMS通过IBinder.DeathRecipient接口接收到进程消亡回调，调用appDiedLocked方法。接着在handleAppDiedLocked和cleanUpApplicationRecordLocked中进行一系列操作，最终通过startProcessLocked重新启动应用进程。这个过程涉及应用启动超时的ANR检测机制。

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应用进程异常被kill后ams重新拉起机制分析

在AMS中有用于专门接收进程消亡回调的类如下：

private final class AppDeathRecipient implements IBinder.DeathRecipient {
        final ProcessRecord mApp;
        final int mPid;
        final IApplicationThread mAppThread;

        AppDeathRecipient(ProcessRecord app, int pid,
                IApplicationThread thread) {
            if (DEBUG_ALL) Slog.v(
                TAG, "New death recipient " + this
                + " for thread " + thread.asBinder());
            mApp = app;
            mPid = pid;
            mAppThread = thread;
        }

        @Override
        public void binderDied() {
            if (DEBUG_ALL) Slog.v(
                TAG, "Death received in " + this
                + " for thread " + mAppThread.asBinder());
            synchronized(ActivityManagerService.this) {
                appDiedLocked(mApp, mPid, mAppThread, true);
            }
        }
    }

IBinder.DeathRecipient如下,从字面理解意思是，当托管IBinder的进程消失时接收回调的接口，具体如何从binder中获知进程的消失，本文暂时不深究，主要目的是搞清楚应用进程被kill后，是如何再次被AMS拉起的。

/**
     * Interface for receiving a callback when the process hosting an IBinder
     * has gone away.
     * 
     * @see #linkToDeath
     */
    public interface DeathRecipient {
        public void binderDied();
    }

可知，当应用被kill后，就会调用到AMS的appDiedLocked方法中:

final void appDiedLocked(ProcessRecord app, int pid, IApplicationThread thread,
            boolean fromBinderDied) {
        // First check if this ProcessRecord is actually active for the pid.
        synchronized (mPidsSelfLocked) {
            ProcessRecord curProc = mPidsSelfLocked.get(pid);
            if (curProc != app) {
                Slog.w(TAG, "Spurious death for " + app + ", curProc for " + pid + ": " + curProc);
                return;