android 设置系统时间的流程

代码摘抄至系统源码
frameworks\base\core\java\android\app\timedetector\TimeDetector.java

if (when / 1000 < Integer.MAX_VALUE) {
             TimeDetector timeDetector = mContext.getSystemService(TimeDetector.class);
             ManualTimeSuggestion manualTimeSuggestion =
             TimeDetector.createManualTimeSuggestion(when, "Settings: Set time");
             timeDetector.suggestManualTime(manualTimeSuggestion);
         }

        

          
        
        
        

          

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/**
     * A shared utility method to create a {@link ManualTimeSuggestion}.
     *
     * @hide
     */
    static ManualTimeSuggestion createManualTimeSuggestion(long when, String why) {
        TimestampedValue<Long> utcTime =
                new TimestampedValue<>(SystemClock.elapsedRealtime(), when);
        ManualTimeSuggestion manualTimeSuggestion = new ManualTimeSuggestion(utcTime);
        manualTimeSuggestion.addDebugInfo(why);
        return manualTimeSuggestion;
    }

        

          
        
        
        

          

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@RequiresPermission(android.Manifest.permission.SUGGEST_MANUAL_TIME_AND_ZONE)
    boolean suggestManualTime(@NonNull ManualTimeSuggestion timeSuggestion);

        

          
        
        
        

          

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frameworks\base\core\java\android\app\timedetector\TimeDetectorImpl.java

@Override
    public boolean suggestManualTime(@NonNull ManualTimeSuggestion timeSuggestion) {
        if (DEBUG) {
            Log.d(TAG, "suggestManualTime called: " + timeSuggestion);
        }
        try {
            return mITimeDetectorService.suggestManualTime(timeSuggestion);
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

        

          
        
        
        

          

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通过aidl调用mITimeDetectorService的suggestManualTime方法
frameworks\base\services\core\java\com\android\server\timedetector\TimeDetectorService.java

@Override
    public boolean suggestManualTime(@NonNull ManualTimeSuggestion timeSignal) {
        enforceSuggestManualTimePermission();
        Objects.requireNonNull(timeSignal);

        final long token = Binder.clearCallingIdentity();
        try {
            return mTimeDetectorStrategy.suggestManualTime(timeSignal);
        } finally {
            Binder.restoreCallingIdentity(token);
        }
    }

        

          
        
        
        

          

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 @Override
    public synchronized boolean suggestManualTime(@NonNull ManualTimeSuggestion suggestion) {
        final TimestampedValue<Long> newUnixEpochTime = suggestion.getUnixEpochTime();

        if (!validateSuggestionTime(newUnixEpochTime, suggestion)) {
            return false;
        }

        String cause = "Manual time suggestion received: suggestion=" + suggestion;
        return setSystemClockIfRequired(ORIGIN_MANUAL, newUnixEpochTime, cause);
    }

        

          
        
        
        

          

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    @GuardedBy("this")
    private boolean setSystemClockIfRequired(
            @Origin int origin, @NonNull TimestampedValue<Long> time, @NonNull String cause) {

        boolean isOriginAutomatic = isOriginAutomatic(origin);
        if (isOriginAutomatic) {
            if (!mEnvironment.isAutoTimeDetectionEnabled()) {
                if (DBG) {
                    Slog.d(LOG_TAG, "Auto time detection is not enabled."
                            + " origin=" + originToString(origin)
                            + ", time=" + time
                            + ", cause=" + cause);
                }
                return false;
            }
        } else {
            if (mEnvironment.isAutoTimeDetectionEnabled()) {
                if (DBG) {
                    Slog.d(LOG_TAG, "Auto time detection is enabled."
                            + " origin=" + originToString(origin)
                            + ", time=" + time
                            + ", cause=" + cause);
                }
                return false;
            }
        }

        mEnvironment.acquireWakeLock();
        try {
            return setSystemClockUnderWakeLock(origin, time, cause);
        } finally {
            mEnvironment.releaseWakeLock();
        }
    }

    private static boolean isOriginAutomatic(@Origin int origin) {
        return origin != ORIGIN_MANUAL;
    }

    @GuardedBy("this")
    private boolean setSystemClockUnderWakeLock(
            @Origin int origin, @NonNull TimestampedValue<Long> newTime, @NonNull String cause) {

        long elapsedRealtimeMillis = mEnvironment.elapsedRealtimeMillis();
        boolean isOriginAutomatic = isOriginAutomatic(origin);
        long actualSystemClockMillis = mEnvironment.systemClockMillis();
        if (isOriginAutomatic) {
            // CLOCK_PARANOIA : Check to see if this class owns the clock or if something else
            // may be setting the clock.
            if (mLastAutoSystemClockTimeSet != null) {
                long expectedTimeMillis = TimeDetectorStrategy.getTimeAt(
                        mLastAutoSystemClockTimeSet, elapsedRealtimeMillis);
                long absSystemClockDifference =
                        Math.abs(expectedTimeMillis - actualSystemClockMillis);
                if (absSystemClockDifference > SYSTEM_CLOCK_PARANOIA_THRESHOLD_MILLIS) {
                    Slog.w(LOG_TAG,
                            "System clock has not tracked elapsed real time clock. A clock may"
                                    + " be inaccurate or something unexpectedly set the system"
                                    + " clock."
                                    + " elapsedRealtimeMillis=" + elapsedRealtimeMillis
                                    + " expectedTimeMillis=" + expectedTimeMillis
                                    + " actualTimeMillis=" + actualSystemClockMillis
                                    + " cause=" + cause);
                }
            }
        }

        // Adjust for the time that has elapsed since the signal was received.
        long newSystemClockMillis = TimeDetectorStrategy.getTimeAt(newTime, elapsedRealtimeMillis);

        // Check if the new signal would make sufficient difference to the system clock. If it's
        // below the threshold then ignore it.
        long absTimeDifference = Math.abs(newSystemClockMillis - actualSystemClockMillis);
        long systemClockUpdateThreshold = mEnvironment.systemClockUpdateThresholdMillis();
        if (absTimeDifference < systemClockUpdateThreshold) {
            if (DBG) {
                Slog.d(LOG_TAG, "Not setting system clock. New time and"
                        + " system clock are close enough."
                        + " elapsedRealtimeMillis=" + elapsedRealtimeMillis
                        + " newTime=" + newTime
                        + " cause=" + cause
                        + " systemClockUpdateThreshold=" + systemClockUpdateThreshold
                        + " absTimeDifference=" + absTimeDifference);
            }
            return true;
        }

        mEnvironment.setSystemClock(newSystemClockMillis);
        String logMsg = "Set system clock using time=" + newTime
                + " cause=" + cause
                + " elapsedRealtimeMillis=" + elapsedRealtimeMillis
                + " (old) actualSystemClockMillis=" + actualSystemClockMillis
                + " newSystemClockMillis=" + newSystemClockMillis;
        if (DBG) {
            Slog.d(LOG_TAG, logMsg);
        }
        mTimeChangesLog.log(logMsg);

        // CLOCK_PARANOIA : Record the last time this class set the system clock due to an auto-time
        // signal, or clear the record it is being done manually.
        if (isOriginAutomatic(origin)) {
            mLastAutoSystemClockTimeSet = newTime;
        } else {
            mLastAutoSystemClockTimeSet = null;
        }
        return true;
    }

        

          
        
        
        

          

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mEnvironment.setSystemClock(newSystemClockMillis);
frameworks\base\services\core\java\com\android\server\timedetector\EnvironmentImpl.java

@Override
    public void setSystemClock(long newTimeMillis) {
        checkWakeLockHeld();
        mAlarmManager.setTime(newTimeMillis);
    }

        

          
        
        
        

          

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@RequiresPermission(android.Manifest.permission.SET_TIME)
    public void setTime(long millis) {
        try {
            mService.setTime(millis);
        } catch (RemoteException ex) {
            throw ex.rethrowFromSystemServer();
        }
    }

        

          
        
        
        

          

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IAlarmManager 通过aidl通信

frameworks\base\apex\jobscheduler\service\java\com\android\server\alarm\AlarmManagerService.java

@Override
        public boolean setTime(long millis) {
            getContext().enforceCallingOrSelfPermission(
                    "android.permission.SET_TIME",
                    "setTime");

            return setTimeImpl(millis);
        }

        

          
        
        
        

          

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    boolean setTimeImpl(long millis) {
        if (!mInjector.isAlarmDriverPresent()) {
            Slog.w(TAG, "Not setting time since no alarm driver is available.");
            return false;
        }

        synchronized (mLock) {
            final long currentTimeMillis = mInjector.getCurrentTimeMillis();
            mInjector.setKernelTime(millis);
            final TimeZone timeZone = TimeZone.getDefault();
            final int currentTzOffset = timeZone.getOffset(currentTimeMillis);
            final int newTzOffset = timeZone.getOffset(millis);
            if (currentTzOffset != newTzOffset) {
                Slog.i(TAG, "Timezone offset has changed, updating kernel timezone");
                mInjector.setKernelTimezone(-(newTzOffset / 60000));
            }
            // The native implementation of setKernelTime can return -1 even when the kernel
            // time was set correctly, so assume setting kernel time was successful and always
            // return true.
            return true;
        }
    }

        

          
        
        
        

          

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Injector为内部类

void setKernelTime(long millis) {
            if (mNativeData != 0) {
                AlarmManagerService.setKernelTime(mNativeData, millis);
            }
        }

        

          
        
        
        

          

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private static native int setKernelTime(long nativeData, long millis);
转到native层
framework/base/apex/jobscheduler/service/jni/com_android_server_alarm_AlarmManagerService.cpp

static jint android_server_alarm_AlarmManagerService_setKernelTime(JNIEnv*, jobject, jlong nativeData, jlong millis)
{
    AlarmImpl *impl = reinterpret_cast<AlarmImpl *>(nativeData);

    if (millis <= 0 || millis / 1000LL >= std::numeric_limits<time_t>::max()) {
        return -1;
    }

    struct timeval tv;
    tv.tv_sec = (millis / 1000LL);
    tv.tv_usec = ((millis % 1000LL) * 1000LL);

    ALOGD("Setting time of day to sec=%ld", tv.tv_sec);

    int ret = impl->setTime(&tv);
    if (ret < 0) {
        ALOGW("Unable to set rtc to %ld: %s", tv.tv_sec, strerror(errno));
        ret = -1;
    }
    return ret;
}

        

          
        
        
        

          

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int AlarmImpl::setTime(struct timeval *tv)
{
    if (settimeofday(tv, NULL) == -1) {
        ALOGV("settimeofday() failed: %s", strerror(errno));
        return -1;
    }

    android::base::unique_fd fd{open(rtc_dev.c_str(), O_RDWR)};
    if (!fd.ok()) {
        ALOGE("Unable to open %s: %s", rtc_dev.c_str(), strerror(errno));
        return -1;
    }

    struct tm tm;
    if (!gmtime_r(&tv->tv_sec, &tm)) {
        ALOGV("gmtime_r() failed: %s", strerror(errno));
        return -1;
    }

    struct rtc_time rtc = {};
    rtc.tm_sec = tm.tm_sec;
    rtc.tm_min = tm.tm_min;
    rtc.tm_hour = tm.tm_hour;
    rtc.tm_mday = tm.tm_mday;
    rtc.tm_mon = tm.tm_mon;
    rtc.tm_year = tm.tm_year;
    rtc.tm_wday = tm.tm_wday;
    rtc.tm_yday = tm.tm_yday;
    rtc.tm_isdst = tm.tm_isdst;
    if (ioctl(fd, RTC_SET_TIME, &rtc) == -1) {
        ALOGV("RTC_SET_TIME ioctl failed: %s", strerror(errno));
        return -1;
    }

    return 0;
}

        

          
        
        
        

          

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