Fix bug 2025765.

Talkback produced a null pointer exception when being enabled and disabled
repeatedly due to a race condition between the onDestroy() of the service,
and the use of the service itself. The error occurs when one Talkback
thread initiates the destruction of the service (call to onDestroy()) when
it invokes shutdown() on its TextToSpeech instance (the client of the
service). At the same time, Talkback tries to say that "Accessibility" is
unchecked from another thread. During onDestroy(), the reference to the
TTS engine (sNativeSynth) is reset to null, which is used in the service
in speakInternalOnly(), and setLanguage().
The fix consists in the addition of a static variable that signals that
the service has entered onDestroy(). Once this flag is set, all method
invocations on sNativeSynth will be dismissed. Note that access to the
native resources used by sNativeSynth are synchronized at the native
layer, therefore preventing sNativeSynth.shutdown() to interfere with
a sNativeSynth.speak() call already underway.

1 files changed, 42 insertions, 4 deletions

diff --git a/packages/TtsService/src/android/tts/TtsService.java b/packages/TtsService/src/android/tts/TtsService.java
index 1b99d32..70960b5 100755
--- a/packages/TtsService/src/android/tts/TtsService.java
+++ b/packages/TtsService/src/android/tts/TtsService.java
@@ -142,6 +142,8 @@ public class TtsService extends Service implements OnCompletionListener {
     private final ReentrantLock synthesizerLock = new ReentrantLock();
 
     private static SynthProxy sNativeSynth = null;
+    private static Boolean sIsKillingSynth = true;
+
     @Override
     public void onCreate() {
         super.onCreate();
@@ -152,6 +154,7 @@ public class TtsService extends Service implements OnCompletionListener {
         String soLibPath = "/system/lib/libttspico.so";
         if (sNativeSynth == null) {
             sNativeSynth = new SynthProxy(soLibPath);
+            sIsKillingSynth = false;
         }
 
         mSelf = this;
@@ -172,6 +175,9 @@ public class TtsService extends Service implements OnCompletionListener {
     @Override
     public void onDestroy() {
         super.onDestroy();
+
+        sIsKillingSynth = true;
+        Log.i("TtsService", "TtsService.onDestroy()");
         // Don't hog the media player
         cleanUpPlayer();
 
@@ -180,6 +186,7 @@ public class TtsService extends Service implements OnCompletionListener {
 
         // Unregister all callbacks.
         mCallbacks.kill();
+        //Log.i("TtsService", "TtsService.onDestroy() ended");
     }
 
 
@@ -243,6 +250,9 @@ public class TtsService extends Service implements OnCompletionListener {
 
 
     private int setSpeechRate(String callingApp, int rate) {
+        if (sIsKillingSynth) {
+            return TextToSpeech.ERROR;
+        }
         if (isDefaultEnforced()) {
             return sNativeSynth.setSpeechRate(getDefaultRate());
         } else {
@@ -252,23 +262,37 @@ public class TtsService extends Service implements OnCompletionListener {
 
 
     private int setPitch(String callingApp, int pitch) {
+        if (sIsKillingSynth) {
+            return TextToSpeech.ERROR;
+        }
         return sNativeSynth.setPitch(pitch);
     }
 
 
     private int isLanguageAvailable(String lang, String country, String variant) {
+        if (sIsKillingSynth) {
+            return TextToSpeech.LANG_NOT_SUPPORTED;
+        }
         //Log.v("TtsService", "TtsService.isLanguageAvailable(" + lang + ", " + country + ", " +variant+")");
         return sNativeSynth.isLanguageAvailable(lang, country, variant);
     }
 
 
     private String[] getLanguage() {
+        if (sIsKillingSynth) {
+            Log.v("TtsService", "killing synth:: aborting getLanguage()");
+            return null;
+        }
         return sNativeSynth.getLanguage();
     }
 
 
     private int setLanguage(String callingApp, String lang, String country, String variant) {
         Log.v("TtsService", "TtsService.setLanguage(" + lang + ", " + country + ", " + variant + ")");
+        if (sIsKillingSynth) {
+            Log.v("TtsService", "killing synth:: aborting setLanguage()");
+            return TextToSpeech.ERROR;
+        }
         if (isDefaultEnforced()) {
             return sNativeSynth.setLanguage(getDefaultLanguage(), getDefaultCountry(),
                     getDefaultLocVariant());
@@ -402,7 +426,12 @@ public class TtsService extends Service implements OnCompletionListener {
                 }
                 if ((mCurrentSpeechItem != null) &&
                      mCurrentSpeechItem.mCallingApp.equals(callingApp)) {
-                    result = sNativeSynth.stop();
+                    if (sIsKillingSynth) {
+                        Log.v("TtsService", "killing synth:: aborting stop()");
+                        result = TextToSpeech.ERROR;
+                    } else {
+                        result = sNativeSynth.stop();
+                    }
                     mKillList.put(mCurrentSpeechItem, true);
                     if (mPlayer != null) {
                         try {
@@ -451,7 +480,12 @@ public class TtsService extends Service implements OnCompletionListener {
                 if ((mCurrentSpeechItem != null) &&
                     ((mCurrentSpeechItem.mType != SpeechItem.TEXT_TO_FILE) ||
                       mCurrentSpeechItem.mCallingApp.equals(callingApp))) {
-                    result = sNativeSynth.stop();
+                    if (sIsKillingSynth) {
+                        Log.v("TtsService", "killing synth:: aborting stop()");
+                        result = TextToSpeech.ERROR;
+                    } else {
+                        result = sNativeSynth.stop();
+                    }
                     mKillList.put(mCurrentSpeechItem, true);
                     if (mPlayer != null) {
                         try {
@@ -591,7 +625,9 @@ public class TtsService extends Service implements OnCompletionListener {
                         if (speechRate.length() > 0){
                             setSpeechRate("", Integer.parseInt(speechRate));
                         }
-                        sNativeSynth.speak(speechItem.mText, streamType);
+                        if (!sIsKillingSynth) {
+                            sNativeSynth.speak(speechItem.mText, streamType);
+                        }
                     }
                 } catch (InterruptedException e) {
                     Log.e("TtsService", "TTS speakInternalOnly(): tryLock interrupted");
@@ -660,7 +696,9 @@ public class TtsService extends Service implements OnCompletionListener {
                         if (speechRate.length() > 0){
                             setSpeechRate("", Integer.parseInt(speechRate));
                         }
-                        sNativeSynth.synthesizeToFile(speechItem.mText, speechItem.mFilename);
+                        if (!sIsKillingSynth) {
+                            sNativeSynth.synthesizeToFile(speechItem.mText, speechItem.mFilename);
+                        }
                     }
                 } catch (InterruptedException e) {
                     Log.e("TtsService", "TTS synthToFileInternalOnly(): tryLock interrupted");