Always re-establish kernel alarms when considering new alarm set

As a backstop against missed alarm delivery / wakeups or clock slew,
make sure to always schedule a kernel alarm for the next alarm events
of interest when we've reexamined the set of deliverable alarms.

Bug 19201933

Change-Id: I3cd37a63dfb0c8258941497d4ba516ed00e2edad

1 files changed, 4 insertions, 2 deletions

diff --git a/services/core/java/com/android/server/AlarmManagerService.java b/services/core/java/com/android/server/AlarmManagerService.java
index a9a756e..65a5c23 100644
--- a/services/core/java/com/android/server/AlarmManagerService.java
+++ b/services/core/java/com/android/server/AlarmManagerService.java
@@ -1230,7 +1230,8 @@ class AlarmManagerService extends SystemService {
         if (mAlarmBatches.size() > 0) {
             final Batch firstWakeup = findFirstWakeupBatchLocked();
             final Batch firstBatch = mAlarmBatches.get(0);
-            if (firstWakeup != null && mNextWakeup != firstWakeup.start) {
+            // always update the kernel alarms, as a backstop against missed wakeups
+            if (firstWakeup != null) {
                 mNextWakeup = firstWakeup.start;
                 setLocked(ELAPSED_REALTIME_WAKEUP, firstWakeup.start);
             }
@@ -1243,7 +1244,8 @@ class AlarmManagerService extends SystemService {
                 nextNonWakeup = mNextNonWakeupDeliveryTime;
             }
         }
-        if (nextNonWakeup != 0 && mNextNonWakeup != nextNonWakeup) {
+        // always update the kernel alarm, as a backstop against missed wakeups
+        if (nextNonWakeup != 0) {
             mNextNonWakeup = nextNonWakeup;
             setLocked(ELAPSED_REALTIME, nextNonWakeup);
         }