Make NtpTrustedTime safer / expand docs

This commit makes a number of changes:
1) Documents / enforces thread safety, removes or deprecates unsafe
check-then-do methods / adds a way to get the NTP query result
atomically.
2) Delays configuration lookup until point of use: the config can change
due to various possible config overlays, e.g. MCC-based config.

(1) is because the threading model is currently unclear / possibly
unsafe - it looks like NtpTrustedTime is supposed to be single threaded
but it's also a singleton so could be accessed from multiple threads.
If NtpTrustedTime were not a singleton things might be easier but the
@UnsupportedAppUsage makes it difficult to change now.
(2) is to address the same issue as https://r.android.com/1182530,
contributed by Luca Stefani.

Bug: 140712361
Test: build only
Change-Id: Ie09da9db5d853b59829886a020de21a88da5dd51

1 files changed, 12 insertions, 5 deletions

diff --git a/services/robotests/src/com/android/server/location/NtpTimeHelperTest.java b/services/robotests/src/com/android/server/location/NtpTimeHelperTest.java
index a8a258fc5ff7..9c5d4ad6ceeb 100644
--- a/services/robotests/src/com/android/server/location/NtpTimeHelperTest.java
+++ b/services/robotests/src/com/android/server/location/NtpTimeHelperTest.java
@@ -3,6 +3,7 @@ package com.android.server.location;
 import static com.google.common.truth.Truth.assertThat;
 
 import static org.mockito.Mockito.doReturn;
+import static org.mockito.Mockito.mock;
 
 import android.os.Looper;
 import android.os.SystemClock;
@@ -52,8 +53,10 @@ public class NtpTimeHelperTest {
 
     @Test
     public void handleInjectNtpTime_cachedAgeLow_injectTime() throws InterruptedException {
-        doReturn(NtpTimeHelper.NTP_INTERVAL - 1).when(mMockNtpTrustedTime).getCacheAge();
-        doReturn(MOCK_NTP_TIME).when(mMockNtpTrustedTime).getCachedNtpTime();
+        NtpTrustedTime.TimeResult result = mock(NtpTrustedTime.TimeResult.class);
+        doReturn(NtpTimeHelper.NTP_INTERVAL - 1).when(result).getAgeMillis();
+        doReturn(MOCK_NTP_TIME).when(result).getTimeMillis();
+        doReturn(result).when(mMockNtpTrustedTime).getCachedTimeResult();
 
         mNtpTimeHelper.retrieveAndInjectNtpTime();
 
@@ -64,7 +67,9 @@ public class NtpTimeHelperTest {
     @Test
     public void handleInjectNtpTime_injectTimeFailed_injectTimeDelayed()
             throws InterruptedException {
-        doReturn(NtpTimeHelper.NTP_INTERVAL + 1).when(mMockNtpTrustedTime).getCacheAge();
+        NtpTrustedTime.TimeResult result1 = mock(NtpTrustedTime.TimeResult.class);
+        doReturn(NtpTimeHelper.NTP_INTERVAL + 1).when(result1).getAgeMillis();
+        doReturn(result1).when(mMockNtpTrustedTime).getCachedTimeResult();
         doReturn(false).when(mMockNtpTrustedTime).forceRefresh();
 
         mNtpTimeHelper.retrieveAndInjectNtpTime();
@@ -72,8 +77,10 @@ public class NtpTimeHelperTest {
         assertThat(mCountDownLatch.await(2, TimeUnit.SECONDS)).isFalse();
 
         doReturn(true).when(mMockNtpTrustedTime).forceRefresh();
-        doReturn(1L).when(mMockNtpTrustedTime).getCacheAge();
-        doReturn(MOCK_NTP_TIME).when(mMockNtpTrustedTime).getCachedNtpTime();
+        NtpTrustedTime.TimeResult result2 = mock(NtpTrustedTime.TimeResult.class);
+        doReturn(1L).when(result2).getAgeMillis();
+        doReturn(MOCK_NTP_TIME).when(result2).getTimeMillis();
+        doReturn(result2).when(mMockNtpTrustedTime).getCachedTimeResult();
         SystemClock.sleep(NtpTimeHelper.RETRY_INTERVAL);
 
         waitForTasksToBePostedOnHandlerAndRunThem();