am 04eb368d: Merge "Prevent some alarm pathologies" into lmp-mr1-dev

* commit '04eb368d0381b0f94365b4e270afb610fe3564c2':
  Prevent some alarm pathologies

services/core/java/com/android/server/AlarmManagerService.java

@@ -75,6 +75,12 @@ class AlarmManagerService extends SystemService {
     // warning message.  The time duration is in milliseconds.
     private static final long LATE_ALARM_THRESHOLD = 10 * 1000;
 
+    // Minimum futurity of a new alarm
+    private static final long MIN_FUTURITY = 5 * 1000;  // 5 seconds, in millis
+
+    // Minimum alarm recurrence interval
+    private static final long MIN_INTERVAL = 60 * 1000;  // one minute, in millis
+
     private static final int RTC_WAKEUP_MASK = 1 << RTC_WAKEUP;
     private static final int RTC_MASK = 1 << RTC;
     private static final int ELAPSED_REALTIME_WAKEUP_MASK = 1 << ELAPSED_REALTIME_WAKEUP;
@@ -696,6 +702,15 @@ class AlarmManagerService extends SystemService {
             windowLength = AlarmManager.INTERVAL_HOUR;
         }
 
+        // Sanity check the recurrence interval.  This will catch people who supply
+        // seconds when the API expects milliseconds.
+        if (interval > 0 && interval < MIN_INTERVAL) {
+            Slog.w(TAG, "Suspiciously short interval " + interval
+                    + " millis; expanding to " + (int)(MIN_INTERVAL/1000)
+                    + " seconds");
+            interval = MIN_INTERVAL;
+        }
+
         if (type < RTC_WAKEUP || type > ELAPSED_REALTIME) {
             throw new IllegalArgumentException("Invalid alarm type " + type);
         }
@@ -709,7 +724,11 @@ class AlarmManagerService extends SystemService {
         }
 
         final long nowElapsed = SystemClock.elapsedRealtime();
-        final long triggerElapsed = convertToElapsed(triggerAtTime, type);
+        final long nominalTrigger = convertToElapsed(triggerAtTime, type);
+        // Try to prevent spamming by making sure we aren't firing alarms in the immediate future
+        final long minTrigger = nowElapsed + MIN_FUTURITY;
+        final long triggerElapsed = (nominalTrigger > minTrigger) ? nominalTrigger : minTrigger;
+
         final long maxElapsed;
         if (windowLength == AlarmManager.WINDOW_EXACT) {
             maxElapsed = triggerElapsed;