From b7309895fa82beb4b7ceeb5f66ec3b1ecff16738 Mon Sep 17 00:00:00 2001
From: zachh <zachh@google.com>
Date: Tue, 3 Apr 2018 13:51:52 -0700
Subject: Don't deadlock in DialerDatabaseHelper.

The fix is to use FutureSerializer instead of synchronizing on the method. FutureSerializer provides the guarantee that the next AsyncCallable won't even be submitted until the ListenableFuture returned by the previous one completes.

Bug: 73877234
Test: added sleep to update task, and verified that resuming activity > 5 times does not deadlock the app
PiperOrigin-RevId: 191494662
Change-Id: I5dc2bed7e117fd3ba5a3cd6a8c39c82a565ce070
---
 .../dialer/database/DialerDatabaseHelper.java      | 38 ++++++++++++----------
 1 file changed, 20 insertions(+), 18 deletions(-)

diff --git a/java/com/android/dialer/database/DialerDatabaseHelper.java b/java/com/android/dialer/database/DialerDatabaseHelper.java
index efff11ecc..b172d7039 100644
--- a/java/com/android/dialer/database/DialerDatabaseHelper.java
+++ b/java/com/android/dialer/database/DialerDatabaseHelper.java
@@ -32,21 +32,23 @@ import android.provider.ContactsContract.CommonDataKinds.Phone;
 import android.provider.ContactsContract.Contacts;
 import android.provider.ContactsContract.Data;
 import android.provider.ContactsContract.Directory;
-import android.support.annotation.Nullable;
 import android.support.annotation.VisibleForTesting;
 import android.support.annotation.WorkerThread;
 import android.text.TextUtils;
 import com.android.contacts.common.R;
 import com.android.contacts.common.util.StopWatch;
 import com.android.dialer.common.LogUtil;
-import com.android.dialer.common.concurrent.DialerExecutor.Worker;
+import com.android.dialer.common.concurrent.DefaultFutureCallback;
 import com.android.dialer.common.concurrent.DialerExecutorComponent;
+import com.android.dialer.common.concurrent.DialerFutureSerializer;
 import com.android.dialer.common.database.Selection;
 import com.android.dialer.configprovider.ConfigProviderBindings;
 import com.android.dialer.database.FilteredNumberContract.FilteredNumberColumns;
 import com.android.dialer.smartdial.util.SmartDialNameMatcher;
 import com.android.dialer.smartdial.util.SmartDialPrefix;
 import com.android.dialer.util.PermissionsUtil;
+import com.google.common.util.concurrent.Futures;
+import com.google.common.util.concurrent.MoreExecutors;
 import java.util.ArrayList;
 import java.util.HashSet;
 import java.util.Objects;
@@ -85,6 +87,8 @@ public class DialerDatabaseHelper extends SQLiteOpenHelper {
   private static final int MAX_ENTRIES = 20;
 
   private final Context context;
+  private final DialerFutureSerializer dialerFutureSerializer = new DialerFutureSerializer();
+
   private boolean isTestInstance = false;
 
   protected DialerDatabaseHelper(Context context, String databaseName, int dbVersion) {
@@ -344,11 +348,19 @@ public class DialerDatabaseHelper extends SQLiteOpenHelper {
    */
   public void startSmartDialUpdateThread(boolean forceUpdate) {
     if (PermissionsUtil.hasContactsReadPermissions(context)) {
-      DialerExecutorComponent.get(context)
-          .dialerExecutorFactory()
-          .createNonUiTaskBuilder(new UpdateSmartDialWorker())
-          .build()
-          .executeParallel(forceUpdate);
+      Futures.addCallback(
+          // Serialize calls to updateSmartDialDatabase. Use FutureSerializer instead of
+          // synchronizing on the method to prevent deadlocking thread pool. FutureSerializer
+          // provides the guarantee that the next AsyncCallable won't even be submitted until the
+          // ListenableFuture returned by the previous one completes. See a bug.
+          dialerFutureSerializer.submit(
+              () -> {
+                updateSmartDialDatabase(forceUpdate);
+                return null;
+              },
+              DialerExecutorComponent.get(context).backgroundExecutor()),
+          new DefaultFutureCallback<>(),
+          MoreExecutors.directExecutor());
     }
   }
 
@@ -657,7 +669,7 @@ public class DialerDatabaseHelper extends SQLiteOpenHelper {
    * @param forceUpdate If set to true, update the database by reloading all contacts.
    */
   @WorkerThread
-  public synchronized void updateSmartDialDatabase(boolean forceUpdate) {
+  public void updateSmartDialDatabase(boolean forceUpdate) {
     LogUtil.enterBlock("DialerDatabaseHelper.updateSmartDialDatabase");
 
     final SQLiteDatabase db = getWritableDatabase();
@@ -1296,14 +1308,4 @@ public class DialerDatabaseHelper extends SQLiteOpenHelper {
       return false;
     }
   }
-
-  private class UpdateSmartDialWorker implements Worker<Boolean, Void> {
-
-    @Nullable
-    @Override
-    public Void doInBackground(Boolean forceUpdate) throws Throwable {
-      updateSmartDialDatabase(forceUpdate);
-      return null;
-    }
-  }
 }
-- 
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