Issue 4041 - Missing engine startup synchronization causing 'blocker not available' message

src/org/adblockplus/sbrowser/contentblocker/ContentBlockerContentProvider.java

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2016 Eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 21 matching lines @@
 import android.net.Uri;
 import android.os.Bundle;
 import android.os.ParcelFileDescriptor;
 import android.preference.PreferenceManager;
 import android.util.Log;
 
 public class ContentBlockerContentProvider extends ContentProvider implements
     EngineService.OnEngineCreatedCallback
 {
   private static final String TAG = ContentBlockerContentProvider.class.getSimpleName();
-  private Engine engine = null;
+  private volatile Engine engine = null;
+  private volatile boolean engineInitDone = false;
 
   @Override
   public Bundle call(String method, String arg, Bundle extras)
   {
     // As of SBC interface v1.4 we return `null` here to signal that we do not
     // use encryption
     return null;
   }
 
   private static boolean getBooleanPref(final SharedPreferences prefs, final String key,
@@ skipping 20 matching lines @@
       prefs.edit()
           .putBoolean(key, true)
           .commit();
     }
   }
 
   @Override
   public ParcelFileDescriptor openFile(final Uri uri, final String mode)
       throws FileNotFoundException
   {
+    if (!this.engineInitDone)
+    {
+      Log.i(TAG, "Engine not ready yet, waiting...");
+      while (!this.engineInitDone)
+      {
+        try
+        {
+          Thread.sleep(10);
+        }
+        catch (InterruptedException e)
+        {
+          Log.e(TAG, "Interrupted: " + e.getMessage(), e);
+          return null;
+        }
+      }
+      Log.i(TAG, "Engine ready");
+    }
+
     if (this.engine == null)
     {
-      Log.e(TAG, "Engine not initialized");
-      throw new FileNotFoundException("Engine not yet initialized");
+      Log.e(TAG, "Engine failed to initialized");

[Felix Dahlke, 2016/05/13 14:29:09]

Nit: "failed to initialize" (minus the last d)

+      return null;
     }
 
     try
     {
       this.setApplicationActivated();
       Log.d(TAG, "Writing filters...");
       final File filterFile = this.engine.createAndWriteFile();
       Log.d(TAG, "Delivering filters...");
       return ParcelFileDescriptor.open(filterFile, ParcelFileDescriptor.MODE_READ_ONLY);
     }
     catch (IOException e)
     {
       Log.e(TAG, "File creation failed: " + e.getMessage(), e);
       return null;
     }
   }
 
   @Override
   public boolean onCreate()
   {
-    EngineService.startService(this.getContext().getApplicationContext(), this);
+    Log.i(TAG, "onCreate() called");
+    EngineService.startService(this.getContext().getApplicationContext(), this, false);
+    Log.i(TAG, "Requested service startup");
     return true;
   }
 
   @Override
   public Cursor query(final Uri uri, final String[] projection, final String selection,
       final String[] selectionArgs, final String sortOrder)
   {
     return null;
   }
 
@@ skipping 18 matching lines @@
   @Override
   public int update(final Uri uri, final ContentValues values, final String selection,
       final String[] selectionArgs)
   {
     return 0;
   }
 
   @Override
   public void onEngineCreated(Engine engine, boolean success)
   {
+    Log.i(TAG, "Service started, success: " + success);
+    this.engineInitDone = true;
     if (success)
     {
       this.engine = engine;
     }
   }
 }