Fix alarm throttling.

Alarm throttling wasn't happening if the queue became empty before a new
alarm was scheduled. This fixes that so the min time between alarms is
always enforced.

Bug: 288975061
Test: atest FrameworksMockingServicesTests:AlarmQueueTest
Change-Id: Id01bcf4e7d53ae7d89c99cb7f97b86163c43ea88
(cherry picked from commit ef46dcbc567938823b600eca5d3349d661a5aeaf)

2 files changed, 29 insertions, 1 deletions

diff --git a/services/core/java/com/android/server/utils/AlarmQueue.java b/services/core/java/com/android/server/utils/AlarmQueue.java
index 09ba19508476..83605ae09e97 100644
--- a/services/core/java/com/android/server/utils/AlarmQueue.java
+++ b/services/core/java/com/android/server/utils/AlarmQueue.java
@@ -151,6 +151,10 @@ public abstract class AlarmQueue<K> implements AlarmManager.OnAlarmListener {
     @GuardedBy("mLock")
     @ElapsedRealtimeLong
     private long mTriggerTimeElapsed = NOT_SCHEDULED;
+    /** The last time an alarm went off (ie. the last time {@link #onAlarm()} was called}). */
+    @GuardedBy("mLock")
+    @ElapsedRealtimeLong
+    private long mLastFireTimeElapsed;
 
     /**
      * @param alarmTag               The tag to use when scheduling the alarm with AlarmManager.
@@ -284,7 +288,7 @@ public abstract class AlarmQueue<K> implements AlarmManager.OnAlarmListener {
     /** Sets an alarm with {@link AlarmManager} for the earliest alarm in the queue after now. */
     @GuardedBy("mLock")
     private void setNextAlarmLocked() {
-        setNextAlarmLocked(mInjector.getElapsedRealtime());
+        setNextAlarmLocked(mLastFireTimeElapsed + mMinTimeBetweenAlarmsMs);
     }
 
     /**
@@ -334,6 +338,7 @@ public abstract class AlarmQueue<K> implements AlarmManager.OnAlarmListener {
         final ArraySet<K> expired = new ArraySet<>();
         synchronized (mLock) {
             final long nowElapsed = mInjector.getElapsedRealtime();
+            mLastFireTimeElapsed = nowElapsed;
             while (mAlarmPriorityQueue.size() > 0) {
                 final Pair<K, Long> alarm = mAlarmPriorityQueue.peek();
                 if (alarm.second <= nowElapsed) {
diff --git a/services/tests/mockingservicestests/src/com/android/server/utils/AlarmQueueTest.java b/services/tests/mockingservicestests/src/com/android/server/utils/AlarmQueueTest.java
index a3a49d7035d9..f3aa4274b3cd 100644
--- a/services/tests/mockingservicestests/src/com/android/server/utils/AlarmQueueTest.java
+++ b/services/tests/mockingservicestests/src/com/android/server/utils/AlarmQueueTest.java
@@ -259,6 +259,29 @@ public class AlarmQueueTest {
     }
 
     @Test
+    public void testMinTimeBetweenAlarms_freshAlarm() {
+        final AlarmQueue<String> alarmQueue = createAlarmQueue(true, 5 * MINUTE_IN_MILLIS);
+        final long fixedTimeElapsed = mInjector.getElapsedRealtime();
+
+        InOrder inOrder = inOrder(mAlarmManager);
+
+        final String pkg1 = "com.android.test.1";
+        final String pkg2 = "com.android.test.2";
+        alarmQueue.addAlarm(pkg1, fixedTimeElapsed + MINUTE_IN_MILLIS);
+        inOrder.verify(mAlarmManager, timeout(1000).times(1)).setExact(
+                anyInt(), eq(fixedTimeElapsed + MINUTE_IN_MILLIS), eq(ALARM_TAG), any(), any());
+
+        advanceElapsedClock(MINUTE_IN_MILLIS);
+
+        alarmQueue.onAlarm();
+        // Minimum of 5 minutes between alarms, so the next alarm should be 5 minutes after the
+        // first.
+        alarmQueue.addAlarm(pkg2, fixedTimeElapsed + 2 * MINUTE_IN_MILLIS);
+        inOrder.verify(mAlarmManager, timeout(1000).times(1)).setExact(
+                anyInt(), eq(fixedTimeElapsed + 6 * MINUTE_IN_MILLIS), eq(ALARM_TAG), any(), any());
+    }
+
+    @Test
     public void testOnAlarm() {
         final AlarmQueue<String> alarmQueue = createAlarmQueue(true, 0);
         final long nowElapsed = mInjector.getElapsedRealtime();