Fix PrioritizedSerialExecutor.

It was possible that fetchNextTasks() would be called by multiple
threads concurrently.
If it happens, some tasks in the task queues might be ignored.

cherrypick of Idc81c43c45e382da3850cc55b9a42c281548d2a8

bug: 10957075
Change-Id: I41bf90dda15306ee879350f96a791d940ea31da1

3 files changed, 42 insertions, 38 deletions

diff --git a/java/src/com/android/inputmethod/latin/ExpandableBinaryDictionary.java b/java/src/com/android/inputmethod/latin/ExpandableBinaryDictionary.java
index 183f12ad9..712520212 100644
--- a/java/src/com/android/inputmethod/latin/ExpandableBinaryDictionary.java
+++ b/java/src/com/android/inputmethod/latin/ExpandableBinaryDictionary.java
@@ -727,7 +727,7 @@ abstract public class ExpandableBinaryDictionary extends Dictionary {
                         holder.set(mBinaryDictionary.isValidWord(word));
                     } else {
                         holder.set(((DynamicPersonalizationDictionaryWriter) mDictionaryWriter)
-                                .isInDictionaryForTests(word));
+                                .isInBigramListForTests(word));
                     }
                 }
             }
diff --git a/java/src/com/android/inputmethod/latin/personalization/DynamicPersonalizationDictionaryWriter.java b/java/src/com/android/inputmethod/latin/personalization/DynamicPersonalizationDictionaryWriter.java
index 0af028a9e..305088536 100644
--- a/java/src/com/android/inputmethod/latin/personalization/DynamicPersonalizationDictionaryWriter.java
+++ b/java/src/com/android/inputmethod/latin/personalization/DynamicPersonalizationDictionaryWriter.java
@@ -79,7 +79,7 @@ public class DynamicPersonalizationDictionaryWriter extends AbstractDictionaryWr
     public void addUnigramWord(final String word, final String shortcutTarget, final int frequency,
             final boolean isNotAWord) {
         if (mBigramList.size() > mMaxHistoryBigrams * 2) {
-            // Too many entries: just stop adding new vocabrary and wait next refresh.
+            // Too many entries: just stop adding new vocabulary and wait next refresh.
             return;
         }
         mExpandableDictionary.addWord(word, shortcutTarget, frequency);
@@ -90,7 +90,7 @@ public class DynamicPersonalizationDictionaryWriter extends AbstractDictionaryWr
     public void addBigramWords(final String word0, final String word1, final int frequency,
             final boolean isValid, final long lastModifiedTime) {
         if (mBigramList.size() > mMaxHistoryBigrams * 2) {
-            // Too many entries: just stop adding new vocabrary and wait next refresh.
+            // Too many entries: just stop adding new vocabulary and wait next refresh.
             return;
         }
         if (lastModifiedTime > 0) {
@@ -176,8 +176,8 @@ public class DynamicPersonalizationDictionaryWriter extends AbstractDictionaryWr
     }
 
     @UsedForTesting
-    public boolean isInDictionaryForTests(final String word) {
+    public boolean isInBigramListForTests(final String word) {
         // TODO: Use native method to determine whether the word is in dictionary or not
-        return mBigramList.containsKey(word);
+        return mBigramList.containsKey(word) || mBigramList.getBigrams(null).containsKey(word);
     }
 }
diff --git a/java/src/com/android/inputmethod/latin/utils/PrioritizedSerialExecutor.java b/java/src/com/android/inputmethod/latin/utils/PrioritizedSerialExecutor.java
index 5dc0b5893..201a70d42 100644
--- a/java/src/com/android/inputmethod/latin/utils/PrioritizedSerialExecutor.java
+++ b/java/src/com/android/inputmethod/latin/utils/PrioritizedSerialExecutor.java
@@ -16,8 +16,11 @@
 
 package com.android.inputmethod.latin.utils;
 
-import java.util.ArrayDeque;
 import java.util.Queue;
+import java.util.concurrent.ArrayBlockingQueue;
+import java.util.concurrent.ConcurrentLinkedQueue;
+import java.util.concurrent.ThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
 
 /**
  * An object that executes submitted tasks using a thread.
@@ -27,19 +30,20 @@ public class PrioritizedSerialExecutor {
 
     private final Object mLock = new Object();
 
-    // The default value of capacities of task queues.
-    private static final int TASK_QUEUE_CAPACITY = 1000;
     private final Queue<Runnable> mTasks;
     private final Queue<Runnable> mPrioritizedTasks;
     private boolean mIsShutdown;
+    private final ThreadPoolExecutor mThreadPoolExecutor;
 
     // The task which is running now.
     private Runnable mActive;
 
     public PrioritizedSerialExecutor() {
-        mTasks = new ArrayDeque<Runnable>(TASK_QUEUE_CAPACITY);
-        mPrioritizedTasks = new ArrayDeque<Runnable>(TASK_QUEUE_CAPACITY);
+        mTasks = new ConcurrentLinkedQueue<Runnable>();
+        mPrioritizedTasks = new ConcurrentLinkedQueue<Runnable>();
         mIsShutdown = false;
+        mThreadPoolExecutor = new ThreadPoolExecutor(1 /* corePoolSize */, 1 /* maximumPoolSize */,
+                0 /* keepAliveTime */, TimeUnit.MILLISECONDS, new ArrayBlockingQueue<Runnable>(1));
     }
 
     /**
@@ -59,7 +63,16 @@ public class PrioritizedSerialExecutor {
     public void execute(final Runnable r) {
         synchronized(mLock) {
             if (!mIsShutdown) {
-                mTasks.offer(r);
+                mTasks.offer(new Runnable() {
+                    @Override
+                    public void run() {
+                        try {
+                            r.run();
+                        } finally {
+                            scheduleNext();
+                        }
+                    }
+                });
                 if (mActive == null) {
                     scheduleNext();
                 }
@@ -74,45 +87,36 @@ public class PrioritizedSerialExecutor {
     public void executePrioritized(final Runnable r) {
         synchronized(mLock) {
             if (!mIsShutdown) {
-                mPrioritizedTasks.offer(r);
-                if (mActive ==  null) {
+                mPrioritizedTasks.offer(new Runnable() {
+                    @Override
+                    public void run() {
+                        try {
+                            r.run();
+                        } finally {
+                            scheduleNext();
+                        }
+                    }
+                });
+                if (mActive == null) {
                     scheduleNext();
                 }
             }
         }
     }
 
-    private boolean fetchNextTasks() {
-        synchronized(mLock) {
-            mActive = mPrioritizedTasks.poll();
-            if (mActive == null) {
-                mActive = mTasks.poll();
-            }
-            return mActive != null;
+    private boolean fetchNextTasksLocked() {
+        mActive = mPrioritizedTasks.poll();
+        if (mActive == null) {
+            mActive = mTasks.poll();
         }
+        return mActive != null;
     }
 
     private void scheduleNext() {
         synchronized(mLock) {
-            if (!fetchNextTasks()) {
-                return;
+            if (fetchNextTasksLocked()) {
+                mThreadPoolExecutor.execute(mActive);
             }
-            new Thread(new Runnable() {
-                @Override
-                public void run() {
-                    try {
-                        do {
-                            synchronized(mLock) {
-                                if (mActive != null) {
-                                    mActive.run();
-                                }
-                            }
-                        } while (fetchNextTasks());
-                    } finally {
-                        scheduleNext();
-                    }
-                }
-            }).start();
         }
     }