From 9edad83f3ccde21438a86b496c51e3b8559d258f Mon Sep 17 00:00:00 2001
From: Songchun Fan <schfan@google.com>
Date: Wed, 21 Sep 2022 15:04:37 -0700
Subject: [PATCH] [AppsFilter] read sysprop only when it's changed

Bisection shows ag/19669172 likely caused a small regression on the
health metrics possibly due to the overhead of parsing.

Given that system properties don't change much, optimize the reading of
the debug property to be called when any system property is changed.

BUG: 241751330
Test: atest AppEnumerationTests
Change-Id: Ib1c71db0e668b10ddb92fd842fa3a18dd2cf323c
---
 .../core/java/com/android/server/pm/AppsFilterBase.java    | 5 ++---
 .../core/java/com/android/server/pm/AppsFilterImpl.java    | 7 +++++++
 .../java/com/android/server/pm/AppsFilterSnapshotImpl.java | 1 +
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/services/core/java/com/android/server/pm/AppsFilterBase.java b/services/core/java/com/android/server/pm/AppsFilterBase.java
index 14140b5fe2640..5fa5de75eaf35 100644
--- a/services/core/java/com/android/server/pm/AppsFilterBase.java
+++ b/services/core/java/com/android/server/pm/AppsFilterBase.java
@@ -28,7 +28,6 @@ import android.content.pm.SigningDetails;
 import android.os.Binder;
 import android.os.Handler;
 import android.os.Process;
-import android.os.SystemProperties;
 import android.os.Trace;
 import android.os.UserHandle;
 import android.text.TextUtils;
@@ -199,6 +198,7 @@ public abstract class AppsFilterBase implements AppsFilterSnapshot {
     protected SnapshotCache<WatchedSparseBooleanMatrix> mShouldFilterCacheSnapshot;
 
     protected volatile boolean mCacheReady = false;
+    protected volatile boolean mCacheEnabled = true;
 
     protected static final boolean CACHE_VALID = true;
     protected static final boolean CACHE_INVALID = false;
@@ -342,8 +342,7 @@ public abstract class AppsFilterBase implements AppsFilterSnapshot {
                       && !isImplicitlyQueryable(callingAppId, targetPkgSetting.getAppId());
             }
             // use cache
-            if (mCacheReady && SystemProperties.getBoolean("debug.pm.use_app_filter_cache",
-                    true)) {
+            if (mCacheReady && mCacheEnabled) {
                 if (!shouldFilterApplicationUsingCache(callingUid,
                         targetPkgSetting.getAppId(),
                         userId)) {
diff --git a/services/core/java/com/android/server/pm/AppsFilterImpl.java b/services/core/java/com/android/server/pm/AppsFilterImpl.java
index 79d72a3ad7f0c..4c21195e28903 100644
--- a/services/core/java/com/android/server/pm/AppsFilterImpl.java
+++ b/services/core/java/com/android/server/pm/AppsFilterImpl.java
@@ -36,6 +36,7 @@ import android.content.pm.PackageManagerInternal;
 import android.content.pm.SigningDetails;
 import android.content.pm.UserInfo;
 import android.os.Handler;
+import android.os.SystemProperties;
 import android.os.Trace;
 import android.os.UserHandle;
 import android.provider.DeviceConfig;
@@ -223,6 +224,12 @@ public final class AppsFilterImpl extends AppsFilterLocked implements Watchable,
                 return new AppsFilterSnapshotImpl(AppsFilterImpl.this);
             }
         };
+        readCacheEnabledSysProp();
+        SystemProperties.addChangeCallback(this::readCacheEnabledSysProp);
+    }
+
+    private void readCacheEnabledSysProp() {
+        mCacheEnabled = SystemProperties.getBoolean("debug.pm.use_app_filter_cache", true);
     }
 
     /**
diff --git a/services/core/java/com/android/server/pm/AppsFilterSnapshotImpl.java b/services/core/java/com/android/server/pm/AppsFilterSnapshotImpl.java
index 019c853471fe5..4e268a277102b 100644
--- a/services/core/java/com/android/server/pm/AppsFilterSnapshotImpl.java
+++ b/services/core/java/com/android/server/pm/AppsFilterSnapshotImpl.java
@@ -74,6 +74,7 @@ public final class AppsFilterSnapshotImpl extends AppsFilterBase {
             // cache is not ready, use an empty cache for the snapshot
             mShouldFilterCache = new WatchedSparseBooleanMatrix();
         }
+        mCacheEnabled = orig.mCacheEnabled;
         mShouldFilterCacheSnapshot = new SnapshotCache.Sealed<>();
 
         mBackgroundHandler = null;