From b860752a0b25c6c1c8be8995c18a87a70a4f84ac Mon Sep 17 00:00:00 2001
From: Hui Yu <huiyu@google.com>
Date: Wed, 31 Aug 2022 10:59:44 -0700
Subject: [PATCH] Another way to keep track number of foreground services in
 the device.

Add staic field sNumForegroundServices to keep track of number of
foreground services and apps in the device. This field is used
to report statsd atom LmkKillOccurred which can not hold
AMS lock.

Bug: 243768727
Test: statsd_testdrive 51
Change-Id: Id4e53ecf8902c8373e79537a2732586c8cb553d5
---
 .../java/com/android/server/am/ActiveServices.java | 14 ++++++++++++++
 .../java/com/android/server/am/ProcessList.java    | 12 +++++++-----
 2 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/services/core/java/com/android/server/am/ActiveServices.java b/services/core/java/com/android/server/am/ActiveServices.java
index a580f985dd137..3b299a201b7ac 100644
--- a/services/core/java/com/android/server/am/ActiveServices.java
+++ b/services/core/java/com/android/server/am/ActiveServices.java
@@ -192,6 +192,7 @@ import java.util.Comparator;
 import java.util.List;
 import java.util.Objects;
 import java.util.Set;
+import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Predicate;
 
 public final class ActiveServices {
@@ -222,6 +223,11 @@ public final class ActiveServices {
                     | ServiceInfo.FOREGROUND_SERVICE_TYPE_CONNECTED_DEVICE
                     | ServiceInfo.FOREGROUND_SERVICE_TYPE_MEDIA_PROJECTION;
 
+    // Keep track of number of foreground services and number of apps that have foreground
+    // services in the device. This field is made to be directly accessed without holding AMS lock.
+    static final AtomicReference<Pair<Integer, Integer>> sNumForegroundServices =
+            new AtomicReference(new Pair<>(0, 0));
+
     // Foreground service is stopped for unknown reason.
     static final int FGS_STOP_REASON_UNKNOWN = 0;
     // Foreground service is stopped by app calling Service.stopForeground().
@@ -456,6 +462,7 @@ public final class ActiveServices {
         final ArrayList<ServiceRecord> mStartingBackground = new ArrayList<>();
 
         final ArrayMap<String, ActiveForegroundApp> mActiveForegroundApps = new ArrayMap<>();
+
         boolean mActiveForegroundAppsChanged;
 
         static final int MSG_BG_START_TIMEOUT = 1;
@@ -2027,6 +2034,7 @@ public final class ActiveServices {
                         logFGSStateChangeLocked(r,
                                 FrameworkStatsLog.FOREGROUND_SERVICE_STATE_CHANGED__STATE__ENTER,
                                 0, FGS_STOP_REASON_UNKNOWN);
+                        updateNumForegroundServicesLocked();
                     }
                     // Even if the service is already a FGS, we need to update the notification,
                     // so we need to call it again.
@@ -2118,6 +2126,7 @@ public final class ActiveServices {
                     mAm.updateLruProcessLocked(r.app, false, null);
                     updateServiceForegroundLocked(r.app.mServices, true);
                 }
+                updateNumForegroundServicesLocked();
             }
         }
     }
@@ -4836,6 +4845,7 @@ public final class ActiveServices {
         }
 
         smap.ensureNotStartingBackgroundLocked(r);
+        updateNumForegroundServicesLocked();
     }
 
     private void dropFgsNotificationStateLocked(ServiceRecord r) {
@@ -7040,6 +7050,10 @@ public final class ActiveServices {
                 fgsStopReasonToString(fgsStopReason));
     }
 
+    private void updateNumForegroundServicesLocked() {
+        sNumForegroundServices.set(mAm.mProcessList.getNumForegroundServices());
+    }
+
     boolean canAllowWhileInUsePermissionInFgsLocked(int callingPid, int callingUid,
             String callingPackage) {
         return shouldAllowFgsWhileInUsePermissionLocked(callingPackage, callingPid, callingUid,
diff --git a/services/core/java/com/android/server/am/ProcessList.java b/services/core/java/com/android/server/am/ProcessList.java
index ccbca76d18683..a7048a7e27bb9 100644
--- a/services/core/java/com/android/server/am/ProcessList.java
+++ b/services/core/java/com/android/server/am/ProcessList.java
@@ -814,12 +814,14 @@ public final class ProcessList {
                                                 < LmkdStatsReporter.KILL_OCCURRED_MSG_SIZE) {
                                             return false;
                                         }
-                                        Pair<Integer, Integer> temp = getNumForegroundServices();
-                                        final int totalForegroundServices = temp.first;
-                                        final int procsWithForegroundServices = temp.second;
+                                        // Note: directly access
+                                        // ActiveServices.sNumForegroundServices, do not try to
+                                        // hold AMS lock here, otherwise it is a potential deadlock.
+                                        Pair<Integer, Integer> foregroundServices =
+                                                ActiveServices.sNumForegroundServices.get();
                                         LmkdStatsReporter.logKillOccurred(inputData,
-                                                totalForegroundServices,
-                                                procsWithForegroundServices);
+                                                foregroundServices.first,
+                                                foregroundServices.second);
                                         return true;
                                     case LMK_STATE_CHANGED:
                                         if (receivedLen