Android 常驻应用崩溃导致进入recovery过程_android 系统异常进入recovery模式

应用崩溃过程：常驻应用不断崩溃，救援等级增加，最终达到LEVEL_FACTORY_RESET等级。进入recovery（Android 9.0源码）：
frameworks\base\services\core\java\com\android\server\am\AppErrors.java

/**
     * Bring up the "unexpected error" dialog box for a crashing app.
     * Deal with edge cases (intercepts from instrumented applications,
     * ActivityController, error intent receivers, that sort of thing).
     * @param r the application crashing
     * @param crashInfo describing the failure
     */
    void crashApplication(ProcessRecord r, ApplicationErrorReport.CrashInfo crashInfo) {
        final int callingPid = Binder.getCallingPid();
        final int callingUid = Binder.getCallingUid();

        final long origId = Binder.clearCallingIdentity();
        try {
            crashApplicationInner(r, crashInfo, callingPid, callingUid);
        } finally {
            Binder.restoreCallingIdentity(origId);
        }
    }
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    void crashApplicationInner(ProcessRecord r, ApplicationErrorReport.CrashInfo crashInfo,
            int callingPid, int callingUid) {
        long timeMillis = System.currentTimeMillis();
        String shortMsg = crashInfo.exceptionClassName;
        String longMsg = crashInfo.exceptionMessage;
        String stackTrace = crashInfo.stackTrace;
        if (shortMsg != null && longMsg != null) {
            longMsg = shortMsg + ": " + longMsg;
        } else if (shortMsg != null) {
            longMsg = shortMsg;
        }

        // If a persistent app is stuck in a crash loop, the device isn't very
        // usable, so we want to consider sending out a rescue party.
        if (r != null && r.persistent) {
         //常驻应用调用，该地方可以添加自己的代码保存Log日志，shortMsg longMsg stackTrace 
            RescueParty.notePersistentAppCrash(mContext, r.uid);
        }
......................
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 /**
     * Take note of a persistent app crash. If we notice too many of these
     * events happening in rapid succession, we'll send out a rescue party.
     */
    public static void notePersistentAppCrash(Context context, int uid) {
        if (isDisabled()) return;
        Threshold t = sApps.get(uid);
        if (t == null) {
            t = new AppThreshold(uid);
            sApps.put(uid, t);
        }
        if (t.incrementAndTest()) {
            t.reset();
            incrementRescueLevel(t.uid);
            executeRescueLevel(context);
        }
    }
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/**
     * Escalate to the next rescue level. After incrementing the level you'll
     * probably want to call {@link #executeRescueLevel(Context)}.
     * 增加救援等级，执行executeRescueLevel
     */
    private static void incrementRescueLevel(int triggerUid) {
        final int level = MathUtils.constrain(
                SystemProperties.getInt(PROP_RESCUE_LEVEL, LEVEL_NONE) + 1,
                LEVEL_NONE, LEVEL_FACTORY_RESET);
        SystemProperties.set(PROP_RESCUE_LEVEL, Integer.toString(level));

        EventLogTags.writeRescueLevel(level, triggerUid);
        logCriticalInfo(Log.WARN, "Incremented rescue level to "
                + levelToString(level) + " triggered by UID " + triggerUid);
    }

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   private static void executeRescueLevel(Context context) {
        final int level = SystemProperties.getInt(PROP_RESCUE_LEVEL, LEVEL_NONE);
        if (level == LEVEL_NONE) return;

        Slog.w(TAG, "Attempting rescue level " + levelToString(level));
        try {
            executeRescueLevelInternal(context, level);
            EventLogTags.writeRescueSuccess(level);
            logCriticalInfo(Log.DEBUG,
                    "Finished rescue level " + levelToString(level));
        } catch (Throwable t) {
            final String msg = ExceptionUtils.getCompleteMessage(t);
            EventLogTags.writeRescueFailure(level, msg);
            logCriticalInfo(Log.ERROR,
                    "Failed rescue level " + levelToString(level) + ": " + msg);
        }
    }

    private static void executeRescueLevelInternal(Context context, int level) throws Exception {
        switch (level) {
            case LEVEL_RESET_SETTINGS_UNTRUSTED_DEFAULTS:
                resetAllSettings(context, Settings.RESET_MODE_UNTRUSTED_DEFAULTS);
                break;
            case LEVEL_RESET_SETTINGS_UNTRUSTED_CHANGES:
                resetAllSettings(context, Settings.RESET_MODE_UNTRUSTED_CHANGES);
                break;
            case LEVEL_RESET_SETTINGS_TRUSTED_DEFAULTS:
                resetAllSettings(context, Settings.RESET_MODE_TRUSTED_DEFAULTS);
                break;
            case LEVEL_FACTORY_RESET:
            //进入Recovery
                RecoverySystem.rebootPromptAndWipeUserData(context, TAG);
                break;
        }
    }
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 /** {@hide} */
    public static void rebootPromptAndWipeUserData(Context context, String reason)
            throws IOException {
        String reasonArg = null;
        if (!TextUtils.isEmpty(reason)) {
            reasonArg = "--reason=" + sanitizeArg(reason);
        }

        final String localeArg = "--locale=" + Locale.getDefault().toString();
        bootCommand(context, null, "--prompt_and_wipe_data", reasonArg, localeArg);
    }
  /**
     * Reboot into the recovery system with the supplied argument.
     * @param args to pass to the recovery utility.
     * @throws IOException if something goes wrong.
     */
    private static void bootCommand(Context context, String... args) throws IOException {
        LOG_FILE.delete();

        StringBuilder command = new StringBuilder();
        for (String arg : args) {
            if (!TextUtils.isEmpty(arg)) {
                command.append(arg);
                command.append("\n");
            }
        }

        // Write the command into BCB (bootloader control block) and boot from
        // there. Will not return unless failed.
        //进入 Recovery
        RecoverySystem rs = (RecoverySystem) context.getSystemService(Context.RECOVERY_SERVICE);
        rs.rebootRecoveryWithCommand(command.toString());

        throw new IOException("Reboot failed (no permissions?)");
    }
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